Thermoplastic elastomeric blend of monoolefin copolymer rubber, amorphous polypropylene resin and crystalline polyolefin resin
This invention relates to a thermoplastic elastomer composition. 
     Thermoplastic elastomers are materials which can be processed and fabricated by methods used for thermoplastics and do not require any cure in the shaped state to develop elastomeric properties, unlike ordinary elastomers which require cure or vulcanization. Thermoplastic elastomers can be reprocessed since they remain thermoplastic, and therefore scrap and rejects can be recycled, unlike conventional elastomers which are thermoset once they are cured and cannot be reworked. Thermoplastic elastomers therefore combine in an economical manner the processing advantages of a thermoplastic with certain desirable physical properties of a cured elastomer. 
     Thermoplastic elastomers based on blends of saturated or low unsaturation monoolefin copolymer rubber (EPM or EPDM type rubber) with crystalline polyolefin resin are known. Typically they are made by dynamically partially curing the blend of rubber and resin (see, for example, U.S. Pat. No. 3,806,558, Fischer, Apr. 23, 1974; see also Fischer U.S. Pat. Nos. 3,758,643 issed Sept. 11, 1973, 3,835,201 issued Sept. 10, 1974, and 3,862,106 issued Jan. 21, 1975, and U.S. Pat. No. 4,031,169, Morris, June 21, 1977. Shaped articles having elastomeric properties can be fabricated from the resulting thermoplastic blends without further cure. It has been desired to improve the processing behavior of such thermoplastic elastomers. 
     U.S. Pat. No. 3,564,080, Pedretti et al, Feb. 16, 1971, discloses extending or diluting vulcanizable EPM or EPDM type rubber compositions with amorphous polypropylene for the purpose of improving the processability; the compositions are vulcanized in the conventional manner to a thermoset, unprocessable state. 
     U.S. Pat. No. 4,076,669, Harper, Feb. 28, 1978, discloses extending certain hydrogenated SBR rubbery block copolymers with amorphous polypropylene to provide good tensile and flow properties. 
     In accordance with the present invention, it has now been found that improved thermoplastic elastomers having good processing characteristics and desirable physical properties are obtained by blending: 
     A. a monoolefin copolymer rubber; 
     B. an amorphous non-elastomeric polypropylene resin or amorphous non-elastomeric resinous copolymer of propylene with another monoolefin; and 
     C. a crystalline polyolefin resin; 
     the said ingredients A, B and C being present in the following proportions; expressed as percent by weight based on the total weight of A, B and C: 
     15 to 80% of A 
     5 to 45% of B 
     15 to 80% of C 
     These proportions fall within a trapezoid a b c d having the following triangular coordinates, expressed as weight percent, based on the sum of the weights of A, B and C: 
     
         ______________________________________                                    
         a      b        c        d                                       
______________________________________                                    
A          80       40       15     15                                    
B          5        45       45     5                                     
C          15       15       40     80                                    
______________________________________                                    
 
    
     Preferred proportions of A, B and C are: 
     20 to 50% of A 
     5 to 35% of B 
     15 to 75% of C 
     These fall within the trapezoid a b&#39; c&#39; d&#39; represented by the following triangular coordinates: 
     
         ______________________________________                                    
         a      b&#39;       c&#39;       d&#39;                                      
______________________________________                                    
A          80       50       20     20                                    
B          5        35       35     5                                     
C          15       15       45     75                                    
______________________________________                                    
 
    
     In the accompanying drawing the single FIGURE is a graph, on triangular coordinates, representing the proportions of the three polymeric ingredients in the compositions of the invention. In the graph, the trapezoid a b c d represents the broad proportions set forth above, while the trapezoid a b&#39;c&#39;d&#39; represents the preferred proportions. 
    
    
     Particularly valuable compositions of the invention further include up to 70 percent by weight, preferably from 5 to 30 percent by weight, of extender oil, based on the sum of the weights of the polymeric components A, B and C. 
     The blend may be subjected to a dynamic partial curing step as in the above-mentioned Fischer U.S. Pat. No. 3,806,558 but this is not essential. 
     If a dynamic partial curing step is utilized it may be carried out on the monoolefin copolymer rubber component A above before blending with the other two polymeric components B (the amorphous polypropylene homopolymer or copolymer resin) or C (the crystalline polyolefin resin), or the dynamic curing step may be carried out after mixing the monolefin copolymer rubber component A with some or all of either or both of the two other polymeric components B and C. In any event, it will be noted that the present blend is distinguished from the conventional Fischer-type of thermoplastic elastomer in that component B, the amorphous non-elastomeric polypropylene homopolymer or copolymer resin, is included in the final blend, whether a dynamic curing step is undertaken or not. 
     The monoolefin copolymer rubber A employed in the blend of the invention is an amorphous, random, elastomeric copolymer of two or more monoolefins, with or without a copolymerizable polyene. Usually two monoolefins are used, but three or more may be used. Ordinarily one of the monoolefins is ethylene while the other is preferably propylene. However, other alphamonoolefins may be used including those of the formula CH 2  ═CHR where R is an alkyl radical having for example one to 12 carbon atoms (e.g., butene-1, pentene-1, hexene-1, 4-methylpentene-1, 5-methylhexene-1, 4-ethylhexene-1, etc.). While the monoolefin copolymer rubber may be a saturated material, as in ethylene propylene binary copolymer rubber (&#34;EPM&#34;), it is ordinarily preferred to include in the copolymer a small amount of at least one copolymerizable polyene to confer unsaturation on the copolymer (&#34;EPDM&#34;). Although conjugated dienes such as butadiene or isoprene may be used for this purpose (British Pat. No. 983,437, Belgian Pat. No. 736,717, Sumitomo Chemical Co., Jan. 29, 1970), in practice it is usual to employ a non-conjugated diene, including the open-chain non-conjugated diolefins such as 1,4-hexadiene (U.S. Pat. No. 2,933,480 Gresham et al., Apr. 19, 1960) or a cyclic diene, especially a bridged ring cyclic diene, as in dicyclopentadiene (U.S. Pat. No. 3,211,709, Adamek et al., Oct. 12, 1965), or an alkylideneorbornene as in methylenenorbornene or ethylidenenorbornene (U.S. Pat. No. 3,151,173, Nyce, Sept. 29, 1964), as well as cyclooctadeiene, methyltetrahydroindene, etc. (see also such U.S. Pat. Nos. as 3,093,620 and 3,093,621; also 3,538,192 col. 6 line 49 to col. 7, line 51). The polyenes employed are not limited to those having only two double bonds, but include those having three or more double bonds. Typically, conventional monoolefin copolymer rubber has a Brookfield viscosity in excess of 5,000,000 at 375° F., and a Mooney viscosity, of at least 20 ML-4 at 212° F. 
     The crystalline polyolefin resin C used to make the blend of the invention is a solid, high molecular weight resinous plastic material made by polymerizing such olefins as ethylene, propylene, butene-1, pentene-1, 4-methylpentene, etc., in conventional manner. Thus, such crystalline polyolefins as polyethylene (either of the low density e.g., 0.910-0.925 g/cc, medium density 0.926-0.940 g/cc or high density e.g., 0.941-0.965 type) may be used, whether prepared by high pressure processes or low pressure processes, including linear polyethylene. Polypropylene is a preferred polyolefin plastic, having highly crystalline isotactic and syndiotactic forms. Frequently the density of polypropylene is from 0.800 to 0.980 g/cc. Largely isotactic polypropylene having a density of from 0.900 to 0.910 g/cc may be mentioned particularly. Crystalline block copolymers of ethylene and propylene (which are plastics distinguished from amorphous, random ethylene-propylene elastomers) can also be used. Included among the polyolefin resins are the higher alpha-olefin modified polyethylenes and polypropylenes (see &#34;Polyolefins&#34;, N. V. Boenig, Elsevier Publishing Co., N.Y., 1966). 
     Component B, the amorphous, non-elastomeric polypropylene homopolymer or amorphous, non-elastomeric copolymer of propylene with another monoolefin (e.g., ethylene), is characterized by low degree of isotactic or syndiotactic blocks of said propylene or alpha-olefin copolymer. Unlike crystalline polyolefins such as crystalline polypropylene, such amorphous polymers or copolymers are generally soluble below 100° C. with most aliphatic, aromatic, and halogenated hydrocarbons. 
     Whereas largely isotactic crystalline polypropylene has a density of from 0.900 to 0.910 g/cc, amorphous polypropylene has a density below 0.900 g/cc, usually within a range 0.82 to 0.88 g/cc. 
     Amorphous polypropylene is generally obtained as a byproduct in the production of crystalline isotactic polypropylene. Whereas crystalline isotactic polypropylene is not soluble except at high temperatures (above about 120° C.) in any organic solvents, the amorphous polypropylene will dissolve. 
     Amorphous polypropylene is usually obtained by extracting the mixture of crystalline isotactic polypropylene and amorphous polypropylene produced by typical polymerization catalysts with an appropriate solvent. The amorphous polypropylene is that fraction which is soluble in the extraction solvent. 
     Low viscosity is one characterizing property of conventional amorphous polypropylene obtained by extraction from crystalline polypropylene. Viscosity ranges for several grades are summarized in Table A. 
     
                                           Table A                                 
__________________________________________________________________________
Amorphous Polypropylene or Propylene-Ethylene Copolymer Properties        
               Ring &amp; Ball                 GPC,                           
               Softening                                                  
                      Brookfield                                          
                               Intrinsic   Polystyrene                    
                                                   Number                 
                                                         Weight           
          Density                                                         
               Point  Viscosity 375° F.                            
                               Viscosity                                  
                                     Relative                             
                                           equivalent                     
                                                   average                
                                                         average          
Trademark g/cc °F.                                                 
                      cps      dl/g  Viscosity                            
                                           peaks, mol. wt.                
                                                   mol.                   
                                                         mol.             
__________________________________________________________________________
                                                         wt.              
A-Fax 500 0.863                                                           
               305    500-     0.3-  1.03-                                
                                         ca 500 &amp;  --    --               
                      10,000   0.7   1.07                                 
                                         ca 18,000                        
A-Fax 600 0.863                                                           
               205-   50-      0.17  1.017                                
                                         500       --    --               
               220    100                                                 
A-Fax 700 0.84 305    310,000  0.84  --  2940 &amp;    2,470 164,000          
(propylene-                              152,000                          
ethylene copolymer                                                        
resin)                                                                    
A-Fax 800 0.84 --     50       0.15  --  5540 &amp;    2,010  10,300          
                                         190                              
A-Fax 900A                                                                
          0.86 310    1,650    0.39  --  5870      3,460  43,200          
A-Fax 900B                                                                
          0.86 310    3,565    0.42  --  --        --    --               
A-Fax 900D                                                                
          0.86 310    5,450    0.51  --  --        --    --               
__________________________________________________________________________
 
    
     Because of the lack of crystallinity, the softening points as measured by ring and ball are much lower than expected for crystalline isotactic polypropylene. Crystalline isotactic polypropylene has a melting point in the range of about 165°-189° C. Commercially available isotactic polypropylene generally shows a melting transition by differential thermal analysis (DTA) somewhat lower, usually in the range of about 155°-165° C. 
     The non-elastomeric, amorphous copolymer of propylene and ethylene or the like suitable for use in this invention differs from the rubbery copolymers of alpha-olefins, typically propylene and ethylene, in the very low viscosity. Whereas the EPM and EPDM have high viscosity, typically measured on a Mooney viscometer, the amorphous non-elastomeric copolymers employed as Component B herein have viscosity ranges too low to be measured by a Mooney viscometer as a practical matter. Ordinarily the viscosity of amorphous non-rubbery ethylene-propylene copolymer at 375° F. in a Brookfield Thermosel will be less than 500,000 cps, and typically is in the range 300,000-350,000 cps. A typical copolymer rubber EPM or EPDM in contrast would have a Brookfield viscosity at 375° F., one or more order of magnitude higher than 500,000. 
     Typical conventional amorphous polypropylene is a solid low molecular weight polymer of propylene (number average molecular weight of 500-35,000 preferably 1,000-10,000), soluble in lower hydrocarbons such as pentane or xylene, and usually having less than 5% by weight crystalline component. For the purposes of this invention, amorphous polypropylene made by any of the known processes may be used. Preferably, it is the propylene soluble constituent of the total polymer prepared from propylene monomer using a catalyst comprising a titanium halide and alkyl aluminum as disclosed in Scoggin, U.S. Pat. No. 3,280,090 and Moon, U.S. Pat. No. 3,257,372, the disclosures of which are hereby incorporated by reference. It can be made also using a metal oxide type catalyst such as chromic oxide on alumina. 
     An examplary conventional amorphous polypropylene is the hot methanol extraction product of a waste stream of impure amorphous polypropylene recovered from a propylene polymerization process employing a titanium halide/alkyl aluminum catalyst. The methanol extraction is described in U.S. Pat. No. 3,661,884, the disclosure of which is hereby incorporated by reference. Properties are as follows: 
     
         ______________________________________                                    
Weight Average - Molecular Wt.                                            
                        about 4,000                                       
Ring &amp; Ball Softening Point                                               
                        187° F.                                    
Melt Viscosity at 200° F.                                          
                        890                                               
Melt Viscosity at 275° F.                                          
                        125                                               
Melt Viscosity at 375° F.                                          
                         35                                               
______________________________________                                    
 
    
     A remarkable feature of the present invention is the effect of amorphous polypropylene or amorphous ethylene-alpha-olefin non-elastomeric copolymer on the blend of crystalline alpha-olefin resin with alpha-olefin copolymer rubber. The chemical structure of the repeating units of amorphous polypropylene is identical with the repeating units of crystalline polypropylene, the difference being the tacticity. The chemical structure is not identical with that of the alpha-olefin copolymer rubber, which unlike the amorphous polypropylene contains two or more alpha-olefin repeating units. It is thus surprising that the physical characteristics of the blend indicate that all the amorphous polypropylene blends only with the alpha-olefin rubber phase of the blend, and none with the crystalline alpha-olefin resin. Thus, modulus and tensile of the blend, measured at room temperature depend only upon the percentage composition of crystalline alpha-olefin, and does not depend upon the relative percentage composition of alpha-olefin and amorphous polypropylene. If amorphous polypropylene, being much softer than crystalline polypropylene, had mixed with crystalline polypropylene the hardness of the blend would be expected to decrease. The hardness, measured in Shore A or Shore D units is not, however, decreased. 
     The remarkable utility of the blends of the invention will be manifest from the physical properties of representative blends as illustrated by the examples below. Replacing a portion of the alpha-olefin copolymer rubber A by amorphous polypropylene B in effect extends the rubber, while substantially maintaining good tensile strength and modulus, with generally no adverse effect upon hardness, and with generally increased elongation. In the conventional thermoplastic elastomeric blends based on monolefin copolymer rubber A and crystalline polyolefin resin C, the use of other extenders such as hydrocarbon oil as a partical replacement of the alpha-olefin copolymer rubber unfortunately decreases the hardness and leads to tensiles substantially lower than the mixes without such extenders. In contrast, such hydrocarbon oils can be used advantageously in blends of this invention. It is a remarkable feature of the present invention that incorporation of oil into a blend in which a portion of alpha-olefin copolymer rubber A has been replaced by amorphous polypropylene B does not lead to a decrease in hardness nor loss of tensile strength of the magnitude such oil produces in a comparable blend containing only alpha-olefin copolymer rubber in addition to crystalline polypropylene. 
     Blends of this invention containing amorphous polypropylene are generally somewhat harder than comparable blends containing alpha-olefin copolymer rubber with levels of crystalline polypropylene and oil equivalent to the blend containing a portion of amorphous polypropylene in place of an equivalent portion of alpha-olefin copolymer rubber. By adjusting proportionate amounts of amorphous polypropylene, alpha-olefin copolymer rubber, and oil with a fixed amount of crystalline polypropylene, blends can be prepared which are equivalent in hardness to a blend containing the fixed amount of crystalline polypropylene, alpha-olefin copolymer rubber, and oil, but said blend can be made to contain a much higher proportion of oil plus amorphous polypropylene. 
     Greatly improved flow characteristics are exhibited by the composition of the present invention over comparable blends not containing amorphous polypropylene. This improved flow is characterized by greatly decreased capillary viscosity measured by a McKelvey rheometer at suitable temperature. The decreased viscosity makes fabrication of injection-molded objects much faster and easier, both by improving flow into a mold, and by decreasing the pressure needed to fill the mold with the thermoplastic elastomer. 
     Usually the following procedure is applied in carrying out the invention: 
     (1) The monoolefin copolymer elastomer, the polyalpha-olefin plastic, the amorphous polypropylene or amorphous propylene alpha-olefin compolymer, and if so desired, the curing agent and/or filler, are charged at the desired ratio to a suitable mixer such as Banbury internal mixer, transfer-type extruder-mixer, extruder, or any such device that will enable efficient mastication at the desired temperature. Such blending apparatus may be preheated to reduce the time required to reach a processing temperature range, provided that such preheating temperature is below the decomposition temperature of the curing agent used. 
     (2) While mixing, the temperature is increased to above the decomposition temperature of the curing agent, if used, and usually the mix is held at such a temperature, while continuing the mixing, for a time period long enough to ensure at least 95% decomposition of the curing agent, based on its theoretical half life at said temperature, and thorough mixing of the blend. If no curing agent is used, the mix is simply worked at a temperature sufficiently elevated to soften the ingredients and mix them intimately. 
     (3) After having processed the blend to a degree described under (2), an antioxidant is ordinarily added to the blend and processing is continued usually for one minute or more in order to thoroughly incorporate the antioxidant in the blend for the purpose of deactivating any residual curing agent and enhancing protection against oxidative degradation of the composition. 
     (4) If so desired the resultant product may be refined on a mill before being used to form shaped articles by means of extrusion, injection molding, press molding or any suitable means of manufacture. 
     If a dynamic semi-curing step is carried out, suitable curing agents and curing conditions are as described in Fischer U.S. Pat. No. 3,806,558 (including col. 3, line 21 to col 4, line 24 and col 5, line 25 to col 6, line 51), the disclosure of which is hereby incorporated herein by reference. Briefly, such curatives include any conventional curing or vulcanizing agents effective in the monoolefin copolymer rubber A, especially peroxides, with or without sulfur or other co-curing agents or activators. It will be understood that the thus dynamically semi-cured blend remains a thermoplastic materal that can be reprocessed repeatedly, but it has elastomeric properties without requiring further cure. Without desiring to be limited to any particular theory of operation, it appears that the shearing imparted during the dynamic cure (cure while masticating or working) may break down a certain amount of the cross-linkages, so that the material remains thermoplastic in spite of the curing reaction. For this purpose any conventional curative or radiation may generally be employed. Examples of conventional curatives include such free-radical generating agents or cross-linking agents as the peroxides, whether aromatic or aliphatic as in the aromatic diacyl peroxides and aliphatic diacyl peroxides, dibasic acid peroxides, ketone peroxides, alkyl peroxyesters, alkyl hydroperoxides, e.g., diacetylperoxide, dibenzoylperoxide, bis-2,4-dichlorobenzoylperoxide, di-tert-butylperoxide, dicumylperoxide, tert-butylperbenzoate, tert-butylcumylperoxide, 2,5-bis(tert-butylperoxy)2,5-dimethylhexane, 2,5-bis-(tert-butylperoxy)-2,5-dimethylhexyne-3; 4,4,4&#39;,4&#39;-tetra-(tert-butylperoxy)-2,2-dicyclohexylpropane, 1,4-bis-(tert-butylperoxyisopropyl)-benzene, 1,1-bis-(tert-butylperoxy) 3,3,5-trimethylcyclohexane, lauroyl peroxide, succinic acid peroxide, cyclohexanone peroxide, tert-butyl peracetate, butyl hydroperoxide, etc. Also suitable are the azide types of curing agents including such materials as the azidoformates (e.g., tetramethylenebis (azidofomrate); for others see U.S. Pat. No. 3,284,421, Breslow, Nov. 8, 1966), aromatic polyazides (e.g., 4,4&#39;-diphenylmethan diazide; for others see U.S. Pat. No. 3,297,674, Breslow et al., Jan. 10, 1967), and sulfonazides such as p,p&#39;-oxybis(benzene sulfonyl azide), etc. Other curatives that may be used include the aldehydeamine reaction products such as formaldehyde-ammonia formaldehyde-ethylchloride-ammonia, acetaldehyde-ammonia, formaldehyde-aniline, butyraldehyde-aniline, heptaldehydeaniline, heptaldehyde-formaldehyde-aniline, hexamethylenetetramine, alpha-ethyl-beta-propyl-acrolein-aniline; the substituted ureas (e.g., trimethylthiourea, diethylthiourea, dibutylthiourea, tripentylthiourea, 1,3-bis (2-benzothiazolylmercaptomethyl) urea, and N,N-diphenylthiourea); guanidines (e.g., diphenylguanidine, di-o-tolylguanidine, diphenylguanidine phthalate, and di-o-tolylguanidine salt of dicatechol borate); xanthates (e.g. zinc ethylxanthate, sodium isopropylxanthate, butylxanthic disulfide, potassium isopropylxanthate, and zinc butylxanthate; dithiocarbamates (e.g., copper dimethyl-, zinc dimethyl-, tollurium diethyl-, cadmium dicyclohexyl-, lead dimethyl-, selenium dibutyl-, zinc pentamethylene-, zinc didecyl-, and zinc isopropyloctyl-, dithiocarbamate); thiazoles (e.g., 2-mercaptobenzothiazole; zinc mercaptothiazolyl mercaptide, 2-benzothiazolyl-N,N-diethylthiocarbamyl sulfide, and 2,2&#39;-dithiobis(benzothiazole); imidazoles (e.g., 2-mercaptoimidazoline and 2-mercapto-4,4,6-trimethyldihydropyrimidine); sulfenamides (e.g., N-t-butyl-2-benzothiazole-, N-cyclohexylbenzothiazole-, N,N-di-isopropylbenzothiazole-, N-(2,6-dimethylmorpholino)-2-benzothiazole-, and N,N-diethylbenzothiazole-sulfenamide); thiuramdisulfides (e.g., N,N&#39;-diethyl-, tetrabutyl-, N,N&#39;-di-isopropyldioethyl-, tetramethyl-, N,N&#39;-dicyclohexyl-, and N,N&#39;-tetralaurylthiuramdisulfide); also paraquinone-dioxime, dibenzoparaquinonedioxime, etc. as well as sulfur itself (see Encyclopedia of Chemical Technology, Vol. 17, 2nd edition, Interscience Publishers, 1968; also Organic Peroxides, Daniel Severn, Vol. 1, Wiley-Interscience, 1970). The peroxide curative may be used alone, or in conjunction with the usual auxiliary substances such as sulfur, maleimides including bis-maleimides, poly-unsaturated compounds (e.g., cyanurate), acrylic esters (e.g., trimethylolpropanetrimethacrylate), etc. With sulfur curatives, such as sulfur itself or sulfur donors, it is usually desirable to include an accelerator of sulfur vulcanization as well as an activator (e.g., a metal salt or oxide), as in conventional practice. Mixed peroxide-type or mixed sulfur-type curing systems may be employed if desired such as dicumylperoxide plus 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane or sulfur plus tetramethylthiuramdisulfide. The preferred monnolefin copolymers having residual unsaturation, conferred by the presence of a polyene, such as EPDM, afford the widest choice of curatives. Reference may be had to &#34;Vulcanization and Vulcanizing Agents,&#34; W. Hoffman, Palmerton Publishing Co., New York, 1967, for an extensive disclosure of curing agents. The time and temperature required for cure are in accordance with known practice, and will depend mainly in the particular curative selected as well as other details of the formulation, as is well understood by those skilled in the art. The curative is believed to affect mainly the monoolefin copolymer rubber component A, but, depending on the particular curative, there may be some cross-linking effect on the resinous components B and/or C as well. In any case the treatment may be regarded as a semi-cure or partial cure, to the extent that the product remains processable and thermoplastic, probably because of breaking down of crosslinks by the masticating action while the dynamic cure is in progress. Thus, the blend does not become crosslinked to the extent that it will no longer knit together into a coherent mass in conventional rubber or plastic processing machinery. 
     Any conventional extender oil may be employed in the composition of the invention. Non-limiting examples are extender and process oils, whether derived from petroleum, obtained from other natural sources or manufactured synthtically, examples of extender and process oils being paraffinic oils and naphthenic oils. Further description of conventional extender oils in softeners will be found in Whitby, &#34;Synthetic Rubber,&#34; Wiley &amp; Sons, New York, 1954, page 383 wherein they are classified into solvents (aromatic hydrocarbons, chlorinated hydrocarbons, aliphatic hydrocarbons, and terpenes and related compounds such as gum turpentine and resin), partial solvents (esters, high-molecular weight ketones, and naphthalenes), and non-solvents (alcohols, phenols, low-molecular weight ketones, branched-chain aliphatic hydrocarbons, amines, and other alcohols). Important extender oils include the paraffinic, naphthenic and aromatic type substantially non-volatile compatible mineral oils described in U.S. Pat. No. 3,438,920, Halper et al, Apr. 15, 1969, especially col. 2, lines 38-48 and the table at cols. 3 and 4, lines 7-40, the disclosure of which is hereby incorporated herein by reference; see also U.S. Pat. No. 2,964,083, Pfau et al, Dec.  13, 1960. 
     The composition may further include other conventional compounding ingredients such as particulate or fibrous fillers (non-limiting examples are calcium carbonate, carbon black, silica, glass, asbestos, clay, talc), pigments, processing aids or lubricants, mold release agents, u.v. screening agents, antioxidants or stabilizers for the rubber or resin or both, etc. Any conventional antioxidant or stabilizer may be used, including, by way of non-limiting example, amine types, phenolic types, sulfides, phenyl alkanes, phosphites, etc. Representative materials are listed in &#34;Rubber: Natural and Synthetic,&#34; Stern, Palmerton Publishing Co., New York, 1967, especially at pages 244-256; see also &#34;Chemistry and Technology of Rubber,&#34; Davis &amp; Blake, Reinhold, New York, 1937, Chapter XII. Included are such materials as 2,2,4-trimethyl-1,2-dihydroquinoline, diphenylamine acetone condensate, aldol-alpha-naphthylamine, octylated diphenylamine, N-phenyl-N&#39;-cyclohexyl-p-phenylenediamine, 2,6-di-tert-butyl-4-methylphenol, styrene-resorcinol resin, o-cresol-monosulfide, di-p-cresol-2-propane, 2,5-di-tert-amyl-hydroquinone, dilauryl-3,3&#39;-thiodipropionate and similar dialkyl thiodipropionates, etc. 
     The form of the invention involving a dynamic semi-curing step is particularly advantageous from the standpoint of providing better melt flow, improved high temperature physicals and better die swell. A preferred elastomer for use in the invention is the low unsaturation type of EPDM terpolymer, containing such non-conjugated dienes as 1,4-hexadiene, dicyclopentadiene or 5-ethylidene-2-norbornene. Preferred curatives for these are the peroxide, sulfur or azide types described above. 
     The following examples, in which all quantities are expressed by weight unless otherwise indicated, will serve to illustrate the practice of the invention in more detail. 
     EXAMPLE 1 
     This example illustrates uncured thermoplastic elastomers of the invention. Table I shows a series of blends, identified by the letters A through AAA, containing the ingredients shown in the table, expressed in parts by weight mixed following the general procedure described above. The ingredients are identified as follows: 
     EPDM is an unsaturated sulfur-vulcanizable elastomeric terpolymer of ethylene, propylene and dicyclopentadiene, in which the ethylene: propylene weight ratio is 53: 47; iodine number 10; Mooney viscosity 90 (ML-4 at 212° F.). 
     EPM is a saturated elastomeric copolymer of ethylene and propylene; ethylene: propylene weight ratio 45: 55; Mooney viscosity 66 (ML-4 at 212° F.). 
     Cryst PP 1 is a largely crystalline isotactic polypropylene resin commercially available as Profax (trademark) 6253 having a melt flow index of 4 at 230° C. (ASTM D 123-587) and a density of 0.903 g/cc. 
     Cryst PP 2 is a largely crystalline isotactic polypropylene resin, Profax 6323, having a melt flow index of 11 at 230° C. and a density of 0.903 g/cc. 
     Amor PP 1 is an essentially amorphous polypropylene commercially available as A-Fax (trademark) 500, described in Table A above. 
     Amor PP2 is an essentially amorphous polypropylene A-Fax 600, described in Table A above. 
     Amor P(PE) Co is an essentially amorphous propylene-ethylene copolymer A-Fax 700 containing from 15 to 25% by weight of ethylene described in Table A above. 
     Amor PP3 is an essentially amorphous polypropylene, A-Fax 800, described in Table A above. 
     Amor PP4 is an essentially amorphous polypropylene, A-Fax 900-A, described in Table A above. 
     Amor PP5 is an essentially amorphous polypropylene, A-Fax 900-D, described in Table A above. 
     The filler is magnesium silicate maximum particle size 6 microns, commercially available as Mistron Vapor (trademark). 
     Oil 1, a petroleum hydrocarbon extender oil, is a mixed paraffinic and naphthenic processing oil, Tufflo (trademark) 6056, liquid viscosity (100° F.) 505 SUS; specific gravity (60° F.) 0.8762; flash point 450° F., molecular weight 550. 
     Oil 2 is a petroleum hydrocarbon extender oil, Sun Par 150, a paraffinic oil containing 16.3% aromatic; liquid viscosity (100° F.) 515 SUS; specific gravity (60° F.) 0.880; molecular weight 505. 
     Mixes A through QQ further contain 1.5 parts of conventional antioxidant as described above (e.g., diphenylamine acetone condensate); the remaining mixes RR through AAA contain 1.25 parts of the antioxidant. 
     A Banbury mixer is charged at 0-80 psi steam, with the EPDM or EPM, crystalline polypropylene, amorphous polypropylene, filler if used and antioxidants. 
     If used, the oil, a portion or all, is usually added last. Two or more of the components may be pre-mixed as a masterbatch before adding to the Banbury. Temperature is raised sufficiently to melt the crystalline polypropylene, usually to a temperature of 350° F. or above, mixed for at least one minute at the elevated temperature, and dropped. The hot mix is usually sheeted out to convenient thickness on a mill, heated to about 240°-320° F. 
     The mill sheet is granulated to convenient size for injection molding. Test specimens are typically prepared in screw injection molding machine. 
     
                                           TABLE I                                 
__________________________________________________________________________
         A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R             
__________________________________________________________________________
EPDM     35 30 25 25 30 25 50 40 45 40 40 40       60 50 40               
EPM                                          50 50          60            
Cryst. PP1                                                                
         65 65 65 65 65 65 50 50 50 50 50 50 40 40 40 40 40 40            
Cryst. PP2                                                                
Amor. PP1   5  10 10          10 10       10 10       10 20               
Amor. PP2            5  10          10 10       10                        
Amor. P(PE)Co                                                             
Amor. PP3                                                                 
Amor. PP4                                                                 
Amor. PP5                                                                 
Filler            10             10    10                                 
Oil 1                                     10                              
Oil 2                                                                     
Antioxidant                                                               
         1.5                                                              
            1.5                                                           
               1.5                                                        
                  1.5                                                     
                     1.5                                                  
                        1.5                                               
                           1.5                                            
                              1.5                                         
                                 1.5                                      
                                    1.5                                   
                                       1.5                                
                                          1.5                             
                                             1.5                          
                                                1.5                       
                                                   1.5                    
                                                      1.5                 
                                                         1.5              
                                                            1.5           
Hardness,                                                                 
Shore A                                            91 94 93 91            
Hardness,                                                                 
Shore D  52 50 52 52 52 53 44 45 45 51 50 45 33 34                        
ROOM                                                                      
TEMPERATURE                                                               
100% Modulus,                                                             
         2276                                                             
            2176                                                          
               2275                                                       
                  2442                                                    
                     2472                                                 
                        2488                                              
                           1867                                           
                              1885                                        
                                 1890                                     
                                    1914                                  
                                       1896                               
                                          1889                            
                                             1337                         
                                                1331                      
                                                   1469                   
                                                      1523                
                                                         1568             
                                                            1338          
psig.                                                                     
300% Modulus,                                                             
         2138                                                             
            2181                                                          
               2260                                                       
                  2267                                                    
                     2274                                                 
                        2271                                              
                           1737                                           
                              1798                                        
                                 1780                                     
                                    -- -- 1777                            
                                             1315                         
                                                -- -- -- 1439             
                                                            --            
psig.                                                                     
Tensile, psig.                                                            
         2318                                                             
            2299                                                          
               2392                                                       
                  2415                                                    
                     2425                                                 
                        2462                                              
                           1829                                           
                              1863                                        
                                 1863                                     
                                    1870                                  
                                       1862                               
                                          1893                            
                                             1401                         
                                                1347                      
                                                   1480                   
                                                      1537                
                                                         1565             
                                                            1373          
Ultimate 310                                                              
            260                                                           
               267                                                        
                  213                                                     
                     345                                                  
                        350                                               
                           250                                            
                              252                                         
                                 230                                      
                                    192                                   
                                       212                                
                                          240                             
                                             297                          
                                                282                       
                                                   155                    
                                                      160                 
                                                         265              
                                                            210           
Elongation, %                                                             
Permanent Set, %           150                                            
                              182                                         
                                 145                                      
                                    120                                   
                                       127                                
                                          192                             
                                             185                          
                                                157                       
                                                   60 67 159              
                                                            104           
250° F.                                                            
100% Modulus,                                                             
         744                                                              
            472                                                           
               614                                                        
                  644                                                     
                     705                                                  
                        518                                               
                           474                                            
                              438                                         
                                 422                                      
                                    469                                   
                                       491                                
                                          519                             
                                             308                          
                                                283                       
                                                   384                    
                                                      392                 
                                                         350              
                                                            333           
psig.                                                                     
300% Modulus,                                                             
         796                                                              
            501                                                           
               633                                                        
                  654                                                     
                     699                                                  
                        556                                               
                           518                                            
                              449                                         
                                 428                                      
                                    455                                   
                                       465                                
                                          500                             
                                             -- -- 348                    
                                                      305                 
                                                         378              
                                                            321           
psig.                                                                     
Tensile, psig.                                                            
         1011                                                             
            862                                                           
               1058                                                       
                  996                                                     
                     1026                                                 
                        996                                               
                           648                                            
                              631                                         
                                 581                                      
                                    624                                   
                                       602                                
                                          649                             
                                             337                          
                                                306                       
                                                   519                    
                                                      510                 
                                                         498              
                                                            484           
Ultimate 1007                                                             
            1366                                                          
               1380                                                       
                  1407                                                    
                     1250                                                 
                        1563                                              
                           893                                            
                              1283                                        
                                 1440                                     
                                    1393                                  
                                       903                                
                                          1133                            
                                             1022                         
                                                1000                      
                                                   637                    
                                                      667                 
                                                         880              
                                                            760           
Elongation, %                                                             
Compression Set,                                                          
22 Hrs. R.T.                                                              
__________________________________________________________________________
         S  T  U  V  W  X  Y  Z  AA BB CC DD EE FF GG HH II JJ            
__________________________________________________________________________
EPDM           50 40 30          70 60 45 60 45 50 40 40 00 40            
EPM      50 40          50 40 30                                          
Cryst. PP1                                                                
         40 40 40 40 40 40 40 40 30 30 30 30 30 50 50 50 50 50            
Cryst. PP2                                                                
Amor. PP1                                                                 
         10 20                      10 25          10                     
Amor. PP2      10 20 30 10 20 30          10 25       10                  
Amor. P(PE)Co                                            10               
Amor. PP3                                                                 
Amor. PP4                                                   10            
Amor. PP5                                                                 
Filler                                                                    
Oil 1                                                                     
Oil 2                                                                     
Antioxidant                                                               
         1.5                                                              
            1.5                                                           
               1.5                                                        
                  1.5                                                     
                     1.5                                                  
                        1.5                                               
                           1.5                                            
                              1.5                                         
                                 1.5                                      
                                    1.5                                   
                                       1.5                                
                                          1.5                             
                                             1.5                          
                                                1.5                       
                                                   1.5                    
                                                      1.5                 
                                                         1.5              
                                                            1.5           
Hardness,                                                                 
Shore A  90 91 94 92 92 93 92 -- 84 89 88 87 88 95 95 95 96 96            
Hardness,                                                                 
Shore D                                                                   
ROOM                                                                      
TEMPERATURE                                                               
100% Modulus,                                                             
         1455                                                             
            1418                                                          
               1565                                                       
                  1513                                                    
                     1427                                                 
                        1407                                              
                           1366                                           
                              1331                                        
                                 1080                                     
                                    1152                                  
                                       1107                               
                                          1119                            
                                             1090                         
                                                2057                      
                                                   1991                   
                                                      1956                
                                                         1998             
                                                            2094          
psig.                                                                     
300% Modulus,                                                             
         -- 1435                                                          
               1443                                                       
                  1394                                                    
                     1389                                                 
                        1336                                              
                           1395                                           
                              1339                                        
                                 -- 1077                                  
                                       1044                               
                                          -- 1039                         
                                                -- -- -- -- --            
psig.                                                                     
Tensile, psig.                                                            
         1468                                                             
            1456                                                          
               1570                                                       
                  1511                                                    
                     1442                                                 
                        1461                                              
                           1408                                           
                              1387                                        
                                 1107                                     
                                    1176                                  
                                       1132                               
                                          1150                            
                                             1111                         
                                                1939                      
                                                   1961                   
                                                      1919                
                                                         1956             
                                                            2043          
Ultimate 222                                                              
            327                                                           
               252                                                        
                  275                                                     
                     340                                                  
                        297                                               
                           320                                            
                              395                                         
                                 147                                      
                                    227                                   
                                       282                                
                                          210                             
                                             245                          
                                                197                       
                                                   177                    
                                                      210                 
                                                         197              
                                                            170           
Elongation, %                                                             
Permanent Set, %                                                          
         120                                                              
            219                                                           
               149                                                        
                  172                                                     
                     222                                                  
                        192                                               
                           205                                            
                              275                                         
                                 50 95 146                                
                                          -- 122                          
                                                95 92 120                 
                                                         120              
                                                            92            
250° F.                                                            
100% Modulus,                                                             
         386                                                              
            317                                                           
               371                                                        
                  328                                                     
                     287                                                  
                        350                                               
                           291                                            
                              297                                         
                                 267                                      
                                    288                                   
                                       208                                
                                          243                             
                                             204                          
                                                509                       
                                                   453                    
                                                      462                 
                                                         486              
                                                            445           
psig.                                                                     
300% Modulus,                                                             
         480                                                              
            339                                                           
               403                                                        
                  346                                                     
                     313                                                  
                        393                                               
                           317                                            
                              314                                         
                                 253                                      
                                    266                                   
                                       232                                
                                          219                             
                                             232                          
                                                471                       
                                                   435                    
                                                      484                 
                                                         446              
                                                            462           
psig.                                                                     
Tensile, psig.                                                            
         493                                                              
            477                                                           
               510                                                        
                  478                                                     
                     411                                                  
                        553                                               
                           448                                            
                              506                                         
                                 289                                      
                                    332                                   
                                       305                                
                                          305                             
                                             293                          
                                                491                       
                                                   498                    
                                                      527                 
                                                         520              
                                                            654           
Ultimate 880                                                              
            1072                                                          
               740                                                        
                  910                                                     
                     1030                                                 
                        952                                               
                           1100                                           
                              1155                                        
                                 295                                      
                                    462                                   
                                       785                                
                                          522                             
                                             747                          
                                                837                       
                                                   952                    
                                                      742                 
                                                         1057             
                                                            1057          
Elongation, %                                                             
Compression Set,                                79.5                      
                                                   80.9                   
                                                      68.9                
                                                         79.3             
                                                            75.8          
22 Hrs. R.T.                                                              
__________________________________________________________________________
         KK LL MM NN OO PP QQ RR SS TT UU VV WW XX YY ZZ AAA              
__________________________________________________________________________
EPDM     40 40 40 40 40 40 40 45 40 35 30 40 49 52.5                      
                                                   41 60 37.5             
EPM                                                                       
Cryst. PP1                                                                
         50 50 50 50 50 50 50 40 40 40 40 -- 35 30 45 -- 50               
Cryst. PP2                                40          40                  
Amor. PP1      10             15 20 25 30 20 16 17.5                      
                                                   14    12.5             
Amor. PP2         10                                                      
Amor. P(PE)Co        10                                                   
Amor. PP3   10          10                                                
Amor. PP4                  10                                             
Amor. PP5                                                                 
         10                                                               
Filler                                                                    
Oil 1                                                                     
Oil 2          10 10 10 10 10                                             
Antioxidant                                                               
         1.5                                                              
            1.5                                                           
               1.5                                                        
                  1.5                                                     
                     1.5                                                  
                        1.5                                               
                           1.5                                            
                              1.25                                        
                                 1.25                                     
                                    1.25                                  
                                       1.25                               
                                          1.25                            
                                             1.25                         
                                                1.25                      
                                                   1.25                   
                                                      1.25                
                                                         1.25             
Hardness,                                                                 
Shore A  96 96 96 95 94 96 96 95 95 96 96 94 95 93 94 94 96               
Hardness,                                                                 
Shore D                       33 36 37 38 40 38 35 44 36 48               
ROOM                                                                      
TEMPERATURE                                                               
100% Modulus,                                                             
         1996                                                             
            1965                                                          
               1784                                                       
                  1756                                                    
                     1681                                                 
                        1675                                              
                           1789                                           
                              1447                                        
                                 1419                                     
                                    1379                                  
                                       1355                               
                                          1284                            
                                             1190                         
                                                1013                      
                                                   1611                   
                                                      1309                
                                                         1808             
psig.                                                                     
300% Modulus,                                                             
         -- -- -- 1756                                                    
                     -- 1562                                              
                           1600                                           
                              1353                                        
                                 1321                                     
                                    1259                                  
                                       1302                               
                                          1194                            
                                             1189                         
                                                1033                      
                                                   1486                   
                                                      1269                
                                                         1638             
psig.                                                                     
Tensile, psig.                                                            
         2048                                                             
            1941                                                          
               1786                                                       
                  1797                                                    
                     1640                                                 
                        1698                                              
                           1800                                           
                              1458                                        
                                 1432                                     
                                    1382                                  
                                       1371                               
                                          1270                            
                                             1233                         
                                                1077                      
                                                   1611                   
                                                      1337                
                                                         1824             
Ultimate 182                                                              
            197                                                           
               270                                                        
                  270                                                     
                     277                                                  
                        290                                               
                           245                                            
                              279                                         
                                 320                                      
                                    305                                   
                                       228                                
                                          228                             
                                             291                          
                                                300                       
                                                   310                    
                                                      220                 
                                                         293              
Elongation, %                                                             
Permanent Set, %                                                          
         90 115                                                           
               160                                                        
                  150                                                     
                     175                                                  
                        140                                               
                           140                                            
                              170                                         
                                 165                                      
                                    150                                   
                                       155                                
                                          150                             
                                             140                          
                                                130                       
                                                   175                    
                                                      100                 
                                                         230              
250° F.                                                            
100% Modulus,                                                             
         450                                                              
            456                                                           
               366                                                        
                  274                                                     
                     338                                                  
                        401                                               
                           351                                            
psig.                                                                     
300% Modulus,                                                             
         483                                                              
            473                                                           
               400                                                        
                  300                                                     
                     364                                                  
                        415                                               
                           366                                            
psig.                                                                     
Tensile, psig.                                                            
         560                                                              
            529                                                           
               501                                                        
                  480                                                     
                     454                                                  
                        479                                               
                           393                                            
Ultimate 1035                                                             
            880                                                           
               1015                                                       
                  932                                                     
                     920                                                  
                        857                                               
                           1200                                           
Elongation, %                                                             
Compression Set,                                                          
         75.5                                                             
            78.6                                                          
               82.1                                                       
                  83.2                                                    
                     83.8                                                 
                        83.5                                              
                           79.2                                           
22 Hrs. R.T.                                                              
__________________________________________________________________________
 
    
     EXAMPLE 2 
     In this example, two cured Base Polymer mixtures are first prepared identified as Base Polymer I and II in Table II, both of which contain EPDM and crystalline polypropylene (Cryst PP 1) as identified in Example 1; one of these Base Polymers contains amorphous polypropylene (Amor PP 1 of Example 1), while the other does not. The curing agent is 2,5-bis(tertiarybutylperoxy)-2,5-dimethylhexane (Varox; trademark). 
     Table II shows the amounts of each ingredient, in parts by weight. 
     The procedure involves preparing cured blends A and B in a Banbury by charging first the EPDM, crystalline polypropylene, and amorphous polypropylene if used. The curing agent is added, and the temperature is raised to 350° F. or higher. After 2 minutes at 350° F. or higher the antioxidant is added and mixed, to destroy residual traces of curing agent. The mix is dropped and sheeted on a mill. The sheeted mix is cut into convenient size pieces. These weighed pieces are loaded into a Banbury, along with the other ingredients, of blends C, D, E, F, G, H. The temperature of the Banbury is raised to 350° F. or higher allowing at least two minutes of mixing at elevated temperature. The charge is dropped, sheeted on a mill and granulated. Test pieces are prepared in a screw injection molding machine. 
     Base Polymer I is outside the invention; Base Polymer II is within the invention. 
     Table III shows the physical properties of injection molded specimens of each of the two Base Polymers, as well as a series of mixes made by adding additional ingredients in the amounts shown in Table III, wherein Cryst PP 1 is again the crystalline polypropylene used in Example 1, Amor PP 1 is again the amorphous polypropylene used in Example 1, and Oil 1 is extender oil as identified in Example 1. 
     Final blend A, C and E are outside the invention. It will be observed from the Table III data that good tensile strength is maintained while elongation and flow properties are improved. 
     
                       TABLE II                                                    
______________________________________                                    
Cured Base Polymers                                                       
              I       II                                                  
______________________________________                                    
EPDM            80        60                                              
Crystalline -PP1                                                          
                20        20                                              
Amorphous                                                                 
PP1             --        20                                              
Curing Agent    0.8       0.8                                             
Antioxidant     1.5       1.5                                             
______________________________________                                    
 
    
     
                                           TABLE III                               
__________________________________________________________________________
              A  B  C   D   E  F  G  H                                    
__________________________________________________________________________
Base Polymer I                                                            
              100   75      100                                           
                               100                                        
Base Polymer II  100    75        100                                     
                                     100                                  
Cryst. PP1          25  25                                                
Amor. PP1                      10    10                                   
Oil 1                       20 20 20 20                                   
Hardness, Shore A                                                         
              72 80 94  95  64 68 68 72                                   
Hardness, Shore D                                                         
              25 30 36  40  11 14 11 15                                   
ROOM TEMPERATURE                                                          
100% Modulus, psig.                                                       
              408                                                         
                 429                                                      
                    1440                                                  
                        1269                                              
                            315                                           
                               373                                        
                                  279                                     
                                     302                                  
300% Modulus, psig.                                                       
              -- 598                                                      
                    1477                                                  
                        1368                                              
                            476                                           
                               467                                        
                                  394                                     
                                     375                                  
Tensile, psig.                                                            
              609                                                         
                 606                                                      
                    1478                                                  
                        1403                                              
                            460                                           
                               479                                        
                                  424                                     
                                     408                                  
Ultimate Elongation, %                                                    
              225                                                         
                 315                                                      
                    282 350 254                                           
                               308                                        
                                  330                                     
                                     358                                  
Set, %        30 55 115 150 26 35 54 59                                   
250° F.                                                            
100% Modulus, psig.                                                       
              124                                                         
                 102                                                      
                    333 283 -- -- -- --                                   
300% Modulus, psig.                                                       
              -- 147                                                      
                    420 343 -- -- -- --                                   
Tensile, psig.                                                            
              165                                                         
                 147 480                                                  
                    523 --  -- -- --                                      
Ultimate Elongation, %                                                    
              167                                                         
                 300                                                      
                    473 840 -- -- -- --                                   
COMPRESSION SET                                                           
22 Hrs. Rm. Temp. %                                                       
              45.6                                                        
                 56.9                                                     
                    --  --                                                
70 Hrs. Rm. Temp. %         40.8                                          
                               49.0                                       
                                  54.8                                    
                                     55.7                                 
Capillary Flow                                                            
              9.5                                                         
                 4.5                                                      
                    --  --  5.8                                           
                               4.2                                        
                                  2.9                                     
                                     1.7                                  
poises X 10.sup.3                                                         
(410 Sec.sup.-1 &amp; 350° F.)                                         
Flexural Modulus, psig.                                                   
              -- -- 31,800                                                
                        34,800                                            
__________________________________________________________________________
 
    
     EXAMPLE 3 
     Five masterbatches, identified as Masterbatches I to V in Table IV, are prepared from the ingredients indicated in Table IV, using Varox peroxide curing agent, according to the procedure of Example 2. 
     Masterbatches II, III, IV, and V are within the invention; Masterbatch I is outside the invention. 
     These masterbatches are used to prepare test specimens A to J in Table V, according to the procedure of Example 2. Specimens A and F are outside the invention. Tensile strengths, which are somewhat low in cured samples compared to uncured, can be improved by addition of crystalline polypropylene after the curing step. 
     
                       TABLE IV                                                    
______________________________________                                    
MASTERBATCH→                                                       
             I       II      III   IV    V                                
______________________________________                                    
EPDM 1       80      0       60    50    50                               
Cryst. PP1   20      20      20    20    20                               
Amor. PP1            20            30                                     
Amor. PP2                    20          30                               
Curing Agent 0.8     0.8     0.8   0.8   0.8                              
Antioxidant  1.0     1.0     1.0   1.0   1.0                              
______________________________________                                    
 
    
     
                                           TABLE V                                 
__________________________________________________________________________
RUNS→  A  B  C  D  E  F  G  H   I    J                             
__________________________________________________________________________
Masterbatch I 100            75                                           
Masterbatch II   100            75                                        
Masterbatch III     100            75                                     
Masterbatch IV         100             75                                 
Masterbatch V             100               75                            
Cryst. PP1                   25 25 25  25   25                            
Hardness, Shore A                                                         
              78 82 82 86 84 94 94 94  95   94                            
ROOM TEMPERATURE                                                          
100% Modulus, psig.                                                       
              539                                                         
                 507                                                      
                    455                                                   
                       438                                                
                          381                                             
                             1312                                         
                                1275                                      
                                   1230                                   
                                       1206 1233                          
300% Modulus, psig.                                                       
              -- 681                                                      
                    595                                                   
                       510                                                
                          447                                             
                             1409                                         
                                1313                                      
                                   1248                                   
                                       1245 1240                          
Tensile, psig.                                                            
              700                                                         
                 695                                                      
                    620                                                   
                       529                                                
                          469                                             
                             1483                                         
                                1468                                      
                                   1377                                   
                                       1291 1335                          
Ultimate Elongation, %                                                    
              235                                                         
                 342                                                      
                    355                                                   
                       327                                                
                          372                                             
                             265                                          
                                352                                       
                                   322 357  385                           
Permanent Set, %                                                          
              29 70 65 72 90 107                                          
                                177                                       
                                   166 196  213                           
250°                                                               
100% Modulus, psig.                                                       
              151                                                         
                 111                                                      
                    97 71 61 334                                          
                                310                                       
                                   342 213  316                           
300% Modulus, psig.                                                       
              -- 144                                                      
                    139                                                   
                       77 70 395                                          
                                355                                       
                                   367 212  340                           
                                       NO                                 
Tensile, psig.                                                            
              190                                                         
                 152                                                      
                    139                                                   
                       82 76 448                                          
                                468                                       
                                   478 BREAK                              
                                            516                           
Ultimate Elongation, %                                                    
              197                                                         
                 317                                                      
                    350                                                   
                       455                                                
                          500                                             
                             540                                          
                                750                                       
                                   805 &gt;1600                              
                                            1010                          
Compression Set, %                                                        
              63.7                                                        
                 71.4                                                     
                    73.6                                                  
                       78.2                                               
                          77.3                                            
                             75.7                                         
                                80.7                                      
                                   71.4                                   
                                       84.2 77.1                          
22 Hrs. @ 150° F.                                                  
__________________________________________________________________________
 
    
     EXAMPLE 4 
     In a first stage, mixtures of EPDM rubber and crystalline polypropylene, with or without amorphous polypropylene, in the proportions indicated in Table VI are worked in a Banbury mixer with Varox peroxide curative at 350° F. for 2 minutes to effect a dynamic cure. Antioxidant is added. 
     Thereafter, in a second stage, an additional charge of one or more of the following are added and mixed at 350° F. for 2 minutes, in the proportions indicated in Table VI: 
     (1) crystalline polypropylene 
     (2) amorphous polypropylene 
     (3) oil. 
     Blends A and C are outside the limits of the invention. 
     This example demonstrates a modification of the mixing procedure of examples 2 and 3, in which masterbatches are first prepared, then remixed with additional ingredients added in a second mixing stage. In the present example, a masterbatch is prepared as before, and a second charge is loaded in on top of the first charge, after curing, and after addition of antioxidant. The second charge is mixed well before the charge is dropped, then processed as in the preceding examples 2 and 3. 
     The present example also demonstrates that relatively large quantities of combined amorphous polypropylene and oil can be incorporated into mixes, while maintaining satisfactory physical properties. 
     
                                           TABLE VI                                
__________________________________________________________________________
              FIRST STAGE                                                 
RUN NUMBER→                                                        
              A  B  C  D  E  F  G  H                                      
__________________________________________________________________________
EPDM          60 40 80 60 80 60 70 60                                     
Crystalline PP1                                                           
              25 25 20 20 20 20 20 20                                     
Amorphous PP1    20    20    20 10 15                                     
Curing Agent  0.8                                                         
                 0.8                                                      
                    0.8                                                   
                       0.8                                                
                          0.8                                             
                             0.8                                          
                                0.8                                       
                                   0.8                                    
Antioxidant   1.25                                                        
                 1.25                                                     
                    1.25                                                  
                       1.25                                               
                          1.25                                            
                             1.25                                         
                                1.25                                      
                                   1.25                                   
__________________________________________________________________________
              SECOND STAGE                                                
Crystalline PP1                                                           
              15 15                                                       
Amorphous PP1             20 20 20 20                                     
Oil 1               20 20 10 10 10 20                                     
Hardness, Shore A                                                         
              93 95 67 74 72 78 76 72                                     
Hardness, Shore D                                                         
              34 36 14 16 16 18 18 15                                     
ROOM TEMPERATURE                                                          
100% Modulus, psig.                                                       
              964                                                         
                 1041                                                     
                    257                                                   
                       292                                                
                          314                                             
                             293                                          
                                313                                       
                                   246                                    
300% Modulus, psig.                                                       
              1202                                                        
                 1160                                                     
                    349                                                   
                       372                                                
                          428                                             
                             332                                          
                                389                                       
                                   306                                    
Tensile, psig.                                                            
              1336                                                        
                 1193                                                     
                    340                                                   
                       391                                                
                          417                                             
                             343                                          
                                398                                       
                                   312                                    
Ultimate Elongation, %                                                    
              388                                                         
                 443                                                      
                    245                                                   
                       328                                                
                          318                                             
                             348                                          
                                340                                       
                                   338                                    
Permanent Set, %                                                          
              149                                                         
                 220                                                      
                    25 55 40 75 55 55                                     
__________________________________________________________________________