Organic friction material composition for use to produce friction linings
BACKGROUND OF THE INVENTION 
     a) Field of the invention 
     The present invention relates to a new organic friction material composition useful to produce brake linings, clutch linings and, more generally, any kind of friction linings that must be capable of withstanding high operating temperatures and pressures for substantial periods of time. 
     The invention also relates to friction linings, including brake linings and clutch linings, obtained from such a composition, especially by wet or dry molding. 
     b) Brief description of the prior art 
     It is of common practice to use compositions containing organic or inorganic fibers dispersed in a thermosetting resin to produce friction linings and more particularly brake linings for use in cars, trucks, heavy duty machineries and the like. These compositions that are usually called &#34;organic friction material compositions&#34;, may also contain friction additives such as cashew nut shell powder or oil, copper or brass particles, coal or coal derivatives, and the like, in such an amount as to adjust the friction and the properties of the material to some predetermined values. These compositions may further comprise other additives commonly used in any molding compositions, such as graphite which is known to be a molding lubricant. These compositions may further contain low-cost fillers such as baryte, calcium carbonate, chromite, iron oxide, natural or synthetic rubber, talc, wollastonite and similar materials, whose purpose is exclusively to reduce the amount of resin being used and thus the total cost of the linings made from such compositions. They may further contain natural organic fibers such as cellulose, synthetic organic fibers such as KEVLAR (trade mark), mineral fibers such as mineral wool or glass fibers, or metallic fibers such as steel fibers, for reinforcing purposes. 
     In practise, the friction linings that are obtained from the above mentioned compositions, may be classified in two broad categories, depending on the way they are produced. 
     The first category includes the friction linings obtained by impregnation of a fabric made of woven fibers. According to this process, a fabric made of woven asbestos fibers is reinforced by a wire of brass or copper and is impregnated with a thermosetting resin of the china oil or linseed oil type, that is subsequently polymerized. Use can also be made of sodium silicate instead of the resin. 
     The friction linings that are so-produced are often used in brakes or clutches in which the linings are immersed into a liquid, such as oil (wet applications). Examples of such applications are into public transportation vehicles, military vehicles, industrial vehicles or farm equipments. 
     The other category includes all the friction linings that are obtained by dry or wet molding. 
     Usually, the compositions used for the manufacture of friction linings by dry molding comprises the following four major components: 
     1- a thermosetting resin which is usually a dry resin of the phenolic type; 
     2- reinforcing fibers which usually consist of chrysotile asbestos; 
     3- friction additives suitably selected to provide the requested friction properties; and 
     4- low-cost fillers to reduce the total cost of the linings. 
     The dry-molding process comprises the following steps. 
     1- Dry mixing of all the components in a mixer until a good homogeneity and an adequate bulk density are achieved. 
     2- Cold pressure molding of the mixture into preformed shapes to further reduce the bulk density of the mixture. Such preforms must have some preselected characteristics of hardness, firmness and flexural strength to pass through the subsequent steps. 
     3- Hot molding and final curing. The preforms are introduced into a mold and compressed to a pressure of about 2000 psi at a temperature of 125° to 135° C. for a period of time of about 4 minutes. The final curing is carried out in an oven for about 2 hours at 125° C. 
     To be properly molded, any composition must have good flow properties; it must not lead to the formation of blisters and not stick to the wall of the mold. All of these properties allow for proper qualification of a composition according to its ability to be molded or manufactured industrially. Such properties however are not sufficient to determine whether the composition will result in linings having good mechanical properties and sufficient friction properties, such properties also depending on the relative amount of the basic components of the composition. 
     Friction linings produced by dry-molding as disclosed hereinabove are often used as disc pad brake linings for typical application in cars, or as block brake linings. 
     The composition that are used for the manufacture of friction linings by wet-molding comprises the same four major components as disclosed hereinabove, except for the thermosetting resin which is liquid and may be used with or without solvent. 
     The wet molding process used to produce friction linings from such liquid composition consists in mixing the components in a mixer such as a SIGMA® mixer, then forming the mixture into a calendering machine comprising two rollers and subjecting the so-formed mixture to hot-polymerization under pressure. 
     Friction linings produced by wet-molding are generally used as roll brake linings in passenger cars. 
     In the past, the fiber that has widely been used to prepare organic friction material compositions whatever be their &#34;categories&#34; is asbestos, because of its very low cost and its ability to provide friction linings having good durability and good friction and strength properties. 
     Over the last decade, other fibers have been proposed as substitutes for asbestos to manufacture organic friction material compositions. Examples of such &#34;alternative&#34; compositions are disclosed by way of examples in U.S. Pat. No. 4,119,591 and No. 4,461,643, and in the other prior art references that are mentioned in the preamble of these two patents. 
     U.S. patent application Ser. No. 246,198 filed on Nov. 8, 1988 in the name of the same Applicant, discloses and claims a fibrous-like synthetic forsterite product which is particularly useful as an insulating material. This product which is presently offered for sale under the trademark FRITMAG and will be called as such hereinafter, is obtained by subjecting chrysotile asbestos fibers of any commercial grade, having an MgO: SiO2 ratio lower than 1:1, to calcination at a temperature of from 650° to 1450° C. 
     FRITMAG has a raw loose density of from 3 to 40 pounds per cubic foot, a thermal conductivity K factor of from 0.25 to 0.40 BTU. in/hr. °F.ft 2  and a fusion point of about 1600° to 1700° C. It possesses a somewhat fibrous structure resembling that of the chrysotile asbestos fibers from which it derives, although this fibrous structure has shown to disappear upon rough manipulation, when subjected to pressure, or when mixed with other material. Then, the fibrous structure is lost but the product has and always retains a high insulating value which is quite superior to granular forsterite, or similar to KAOWOOL (trademark) or rockwool. 
     In the above-mentioned U.S. patent application, it is mentioned that FRITMAG may be used as a substitute for asbestos, whenever a fibrous material to be used in bulk and having high insulating qualities is needed. Indeed, FRITMAG has a loose density range substantially identical to asbestos. It also has high insulating properties and is devoided of all the undesirable health problems allegedly attributed to asbestos. In particular, the above-mentioned U.S. patent application suggests to mix FRITMAG with an inert filler and a binder in order to form an insulating composition adapted to be shooted onto any surface to be insulated or to be moulded in the form of slabs for roof insulation. However, no specific example of such a composition is given, and no other use is suggested, except for a very short reference made in the specification to the possibility of mixing FRITMAG with other materials, such as Portland cement. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, it has surprisingly been found that friction linings that have very good wear and friction properties and are capable of withstanding very high temperatures and pressures for substantial periods of time, can be produced from organic friction material compositions of the above mentioned type, containing FRITMAG as a substitute for asbestos. 
     More particularly, it has surprisingly been found that the change of structure that has been noticed in FRITMAG when the same is subject to pressure or mixed with other materials does not affect the properties of friction linings produced from such a composition, even when the same is processed by a dry-or wet-molding process. 
     More particularly, the present invention proposes an organic friction material composition comprising: 
     a) FRITMAG as a substitute for asbestos; 
     b) a thermosetting resin having heat resistant properties; 
     c) at least one friction additive present in such an amount as to adjust the friction and wear properties of the material to some predetermined values; and, if desired 
     d) at least one other additive or filler. 
     In accordance with the invention, it has also been found that the above composition to be efficient, must have a weight ratio of resin to FRITMAG ranging between 0.25 and 0.70, and preferably between 0.50 and 0.60. 
     In accordance with the invention, it has further been found that the ratio of the total weight of all the additive(s) and/or filler(s) present in the composition to the total weight of this composition must be equal to or lower than 0.55. Indeed, it has been found that if this ratio exceeds 0.55, the resulting friction linings may lack some essential properties and thus become unuseful. 
     The organic friction material composition according to the invention may contain any kind of friction additives, other additives and/or fillers commonly used in the art, like those mentioned in the preamble of the present disclosure. 
     The organic friction material composition according to the invention may also contain any kind of thermosetting resin having heat resistance properties, that are presently used in the art. By way of example, such thermosetting resins may be selected from the group consisting of phenol-formaldehyde resins, resorcinol-formaldehyde resins, epoxy resins and mixtures thereof. Such resins can be dry or wet. For dry molding application, use is preferably made of a dry resin of the phenolic type. For wet molding application, use is preferably made of a liquid resin of the thermosetting type like linseed oil. 
     The invention and its advantages will be better understood upon reading the following, non-restrictive examples. 
     COMPARISON EXAMPLE 
     Manufacture of a chrysotile asbestos-containing lining by dry molding and evaluation of mechanical and friction properties of the so manufactured lining 
     I- FORMULATION 
     A typical formulation for the manufacture of a dry asbestos organic lining is as follows (the given percentages being expressed by weight). 
     
                       TABLE 1                                                     
______________________________________                                    
phenolic resin      17.0%                                                 
chrysotile asbestos 52.0%                                                 
friction additives and fillers                                            
                    31.0%                                                 
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     In the present case, use was made of the following products: 
     
         ______________________________________                                    
1-phenolic resin:                                                         
                phenolic resin no. 7716 sold                              
                by BTL Specialty Resin Canada,                            
                a divison of Bakelite                                     
                Thermosets ltd;                                           
2-chrysotile asbestos:                                                    
                asbestos fibers of grade 7R-                              
                410 (according to ASTM D3639);                            
3-additives and fillers:                                                  
                these that were used in the                               
                above formulation are quite                               
                typical and contain the                                   
                following components (the                                 
                percentage being also ex-                                 
                pressed by weight).                                       
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                       TABLE II                                                    
______________________________________                                    
Cashew shell oil 21.0%                                                    
Coal              9.7%                                                    
Graphite         11.3%                                                    
Calcium carbonate                                                         
                 29.0%                                                    
Baryte           29.0%                                                    
                 100.0%                                                   
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     As cashew shell oil, use was made of the oil sold under the trade name NC 104-30 by Cardolite Corp., N.J.. 
     As coal, use was made of the anthracite fines #7 sold by Hickman Williams Co., Montreal. 
     As graphite, use was made of the graphite no. 8020 sold by Asbury Graphite Mills Inc., N.J. 
     As calcium carbonate, use was made of the product sold under the trade name STL 690 by St-Lawrence Chemical. 
     As baryte, use was made of the product sold under the trade name W-125 by Mountain Mineral of Lethbridge (Alberta) and distributed by L. V. Lomas Chemical Cie Ltd. 
     II- PROCESSING 
     All the above mentioned components in requested amounts to produce a 2 kg composition for use to manufacture brake linings were introduced into a concrete mixer. The kinds and percentages of components used in the formulation were as disclosed hereinabove and reported in Tables I and II. 
     The mixture was homogenized for about 4 minutes and 250 g of the homogenized mixture were introduced into a preforming mold (4&#34;×4&#34;) and subjected therein to a pressure of 2500 psi for 15 seconds. 
     Some of the characteristics of the preforms that were so-obtained, were measured or otherwise determined, including: 
     mold ejectability; 
     easiness to remove the preform from the mold; 
     firmness; 
     resistance of the preform to subsequent handling and processing; 
     hardness &#34;B&#34; scale; 
     flexural strength; 
     bulk factor; and 
     apparent density. 
     The preforms that were so obtained were removed from their preforming molds and placed in other molds of identical dimension (4&#34;×4&#34;), for final molding. 
     During this final molding, the preforms were first cured for 1 minute at 125°-130° C. without any pressure applied thereto. Then, compression was started and a pressure of 2000 psi was applied for 3 minutes at a temperature of 125°-135° C. Degazification of the compressed mixture was carried as is known in the art. After extraction from the mold, the samples were cured in an oven for about 2 hours at 125° C. 
     Some of the characteristics of the molded samples that were so obtained were measured or otherwise determined, including: 
     sticking to the wall of the mold; 
     blister formation during molding; 
     density; 
     water absorption; 
     flexural strength; 
     shear strength; and 
     flow and eventually overflow out of the mold. 
     All of the above mentioned measurements or determination were carried out according to the following standards: 
     
         ______________________________________                                    
Performing                                                                
Hardness B scale                                                          
               REX (according to ASTM 2240)                               
Bulk factor    ASTM 1895-C                                                
Apparent Density                                                          
               ASTM 1895-C                                                
Flexural Strenght                                                         
               ASTM D-790                                                 
Preformability estimation                                                 
Ejectability   estimation                                                 
Moldability                                                               
Sticking       estimation                                                 
Blister        estimation                                                 
Density        ASTM D-792                                                 
Water absorption                                                          
               D-570                                                      
Flexural strength                                                         
               ASTM D-790                                                 
Shear strength D3846                                                      
Flow           estimation                                                 
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     For all the data that were not measured but merely estimated, the following classification was adopted: 
     A--excellent 
     B--good 
     C--fair 
     D--weak 
     E--fail. 
     All of these characteristics as they were measured on linings obtained from the prior art formulation given hereinabove are reported in TABLE III, below: 
     
                       TABLE III                                                   
______________________________________                                    
Characteristics of the preforming material and the mechanical             
properties of the asbestos organic lining as reference.                   
COMPOSITION                                                               
AND PROPERTIES   RATIO (I/II) 0.33                                        
______________________________________                                    
1. COMPOSITION                                                            
I) Resin         17.0                                                     
II) Asbestos     52.0                                                     
III) Filler      31.0                                                     
2. PREFORMING                                                             
Ejectability     B                                                        
Firmness         A                                                        
Hardness &#34;B&#34; scale                                                        
                 73                                                       
Bulk factor      4.0                                                      
Apparent density (g/cc)                                                   
                 0.49                                                     
Flexural strenght (psi)                                                   
                 68                                                       
3. MOLDABILITY                                                            
Sticking         A                                                        
Blister          A                                                        
Density (g/cc)   1.98                                                     
Water absorption (%)                                                      
                 0.36                                                     
Flexural strenght (psi)                                                   
                 8900                                                     
Shear strenght (psi)                                                      
                 3650                                                     
Flow             B                                                        
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     III- FRICTION PROPERTIES 
     It is of common practise for the brake system equipment manufacturers to evaluate the friction material performance by measuring or otherwise determining the following characteristics: 
     fade resistance; 
     fade recovery; 
     delayed fade; 
     effectiveness versus speed; 
     friction stability; 
     wet friction; 
     moisture sensitivity; and 
     wear rate. 
     In the present case, these characteristics were measured on the asbestos-containing friction linings obtained as disclosed hereinabove according to the LINK-CHASE test no. SAE J661 a, and the data that were so obtained are reported in TABLE IV. 
     The letter code of the coefficient of friction according to SAE J661 a, is: 
     E, over 0.25 but not over 0.35 
     F, over 0.35 but not over 0.45. 
     
                       TABLE IV                                                    
______________________________________                                    
LINK-CHASE SAE J-661 FRICTION MATERIAL                                    
TEST REPORT ASBESTOS FORMULATION                                          
                      FRICTION                                            
TEST                  COEFFICIENT                                         
______________________________________                                    
INITIAL BASELINE                                                          
APPLICATION 1         0.328                                               
       .sup.  20      0.305                                               
FIRST FADE                                                                
°F. 200        0.300                                               
   550                0.359                                               
FIRST RECOVERY                                                            
°F. 500        0.326                                               
   200                0.266                                               
WEAR                                                                      
APPLICATION 1         0.339                                               
      .sup.  100      0.393                                               
SECOND FADE                                                               
°F. 200        0.252                                               
   650                0.378                                               
SECOND RECOVERY                                                           
°F. 600        0.366                                               
   200                0.269                                               
FINAL BASELINE                                                            
APPLICATION 1         0.267                                               
       .sup.  20      0.308                                               
NORMAL COEFFICIENT    .sup.    0.316(E)                                   
HOT FRICTION COEFFICIENT                                                  
                      .sup.   0.354(F)                                    
WEAR                                                                      
WEIGHT LOSS %         10.8                                                
THICKNESS LOSS %      8.7                                                 
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     EXAMPLE 1 
     Using the same kind of resin and the same kinds and relative concentrations of additives and fillers as disclosed in the comparison example, five different formulations were prepared and processed as disclosed hereinabove, using FRITMAG instead of asbestos as fibers. 
     In these five formulations, the weight percentage of additives and fillers was kept constant (31%). As a result, the weight percentage of resin plus FRITMAG remained also constant (69%). 
     However, the ratio of resin to FRITMAG was varied to be equal to 0.25, 0.35, 0.50, 0.60 and 0.80 for formulation nos. 1 to 5, respectively. 
     The preforming and mechanical properties of the resulting products are given in TABLE V below: 
     
                       TABLE V                                                     
______________________________________                                    
Characteristics of the preforming material and                            
the mechanical properties of the example 1.                               
            No FORMULATION                                                
            1    2        3      4      5                                 
COMPOSITION   RATIO (I/II)                                                
AND PROPERTIES                                                            
              0.25   0.35     0.50 0.60   0.80                            
______________________________________                                    
1. COMPOSITION                                                            
I) Resin (%)  13.8   17.9     23.0 25.9   30.7                            
II) Fritmag (%)                                                           
              55.2   51.1     46.0 43.1   38.3                            
III) Filler (%)                                                           
              31.0   31.0     31.0 31.0   31.0                            
2. PREFORMING                                                             
Ejectability  B      B        B    B      B                               
Firmness      C      C        B    B      B                               
Hardness &#34;B&#34; scale                                                        
              47     55       60   65     70                              
Bulk factor   3.4    3.4      3.6  3.4    --                              
Apparent density (g/cc)                                                   
              0.52   0.54     0.56 0.58   0.59                            
Flexural strenght (psi)                                                   
              10.4   15.8     21.0 21.0   36.1                            
3. MOLDABILITY                                                            
Sticking      A      A        A    A      E                               
Blister       A      A        A    A      E                               
Flow          B      B        A    A      E                               
Density (g/cc)                                                            
              1.79   1.86     1.99 1.95   --                              
Water absorption (%)                                                      
              3.06   1.14     0.24 0.17   --                              
Flexural strenght (psi)                                                   
              5600   7750     8250 8050   --                              
Shear strenght (psi)                                                      
              3300   4850     8800 7100   --                              
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     As can be noted, formulations 3 and 4 have the best preforming properties inasmuch as the firmness, the ejectability and flow were respectively given as &#34;good&#34; (B), &#34;good&#34; (B) and &#34;excellent&#34; (A). These properties may easily be compared to those obtained with the comparison product made from asbestos, where the same properties respectively given as &#34;excellent&#34; (A), &#34;good&#34; (B) and &#34;good&#34; (B) (see TABLE III). 
     Similarly, the flexural strengths of formulations 3 and 4 were equal to 8250 and 8050 psi respectively, as compared to 8900 psi for the asbestos containing product; the shear strengths of formulations 3 and 4 were 8800 and 7100 psi respectively, as compared to 3650 psi for the asbestos containing product. 
     As can also be noted, the properties of formulations 1 and 2 may also generally be classified as good, except for the firmness that is given as &#34;fair&#34; (C) only. 
     Formulation 5 where the ratio of resin to FRITMAG was well over 0.60 was very difficult to mold in the same operating conditions. Thus, it becomes obvious that high ratios of resin to FRITMAG must be avoided. 
     The friction characteristics of the resulting linings measured according to the SAE J661 test are reported in TABLE VI below: 
     
                                           TABLE VI                                
__________________________________________________________________________
LINK-CHASE SAE J-661 FRICTION MATERIAL                                    
TEST REPORT FRITMAG FORMULATION (Example 1)                               
                  FRICTION COEFFICIENT                                    
                  No FORMULATION                                          
TEST              1     2     3     4                                     
__________________________________________________________________________
INITIAL BASELINE                                                          
APPLICATION 1     0.461 0.387 0.321 0.319                                 
       .sup.  20  0.474 0.441 0.326 0.364                                 
FIRST FADE                                                                
°F. 200    0.471 0.439 0.332 0.350                                 
   550            0.384 0.431 0.362 0.385                                 
FIRST RECOVERY                                                            
°F. 500    0.405 0.414 0.344 0.374                                 
   200            0.422 0.420 0.340 0.330                                 
WEAR                                                                      
APPLICATION 1     0.421 0.405 0.350 0.390                                 
      .sup.  100  0.434 0.450 0.421 0.409                                 
SECOND FADE                                                               
°F. 200    0.420 0.442 0.407 0.269                                 
   650            0.418 0.447 0.376 0.416                                 
SECOND RECOVERY                                                           
°F. 600    0.427 0.444 0.378 0.362                                 
   200            0.427 0.400 0.408 0.295                                 
FINAL BASELINE                                                            
APPLICATION 1     0.421 0.396 0.396 0.310                                 
       .sup.  20  0.437 0.404 0.393 0.362                                 
NORMAL COEFFICIENT                                                        
                  .sup. .sup. .sup. .sup.    0.346(E)                     
HOT FRICTION COEFFICIENT                                                  
                  .sup. .sup. .sup. .sup.   0.370(F)                      
WEAR                                                                      
WEIGHT LOSS %     31.3  20.9  8.5   5.9                                   
THICKNESS LOSS %  26.1  20.0  5.0   4.1                                   
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     As can be noted, formulation 3 had good frictional value F-F, acceptable wear rates, and good stable friction throughout the test program; formulation 4 also had good frictional value E-F, good wear rate and relatively good stable friction throughout the test program; formulations 1 and 2 both had good frictional value of F-F and relatively good stable friction throughout the test program. However, both of them also had a high wear rate. 
     By way of comparison, the asbestos-containing formulation used as a reference showed good frictional value E-F, good wear rate and relatively good stable friction throughout the test program. 
     EXAMPLE 2 
     Using the same kind of resin and the same kinds and relative concentrations of additives and fillers as disclosed in the comparison example, four other formulations were prepared and processed as previously explained, using FRITMAG instead of asbestos as fibers. 
     In the formulations numbered 6 and 7 respectively, the ratios of resin to FRITMAG were equal to 0.50 and 0.60 respectively. The percentage of additives and fillers was however increased up to 45% in both cases. In the other formulations numbered 8 and 9 respectively, the ratios of resin to FRITMAG were equal to 0.50 and 0.60 respectively but the percentage of additives and fillers was lowered to 25% in both cases. 
     The preforming and mechanical properties of the resulting products are given in TABLE VII below: 
     
                       TABLE VII                                                   
______________________________________                                    
Characteristics of the preforming material and                            
the mechanical properties of the example 2.                               
              No FORMULATION                                              
              6      7      8         9                                   
COMPOSITION     RATIO (I/II)                                              
AND PROPERTIES  0.50     0.60   0.50    0.60                              
______________________________________                                    
1. COMPOSITION                                                            
I) Resin (%)    18.4     20.6   25.0    28.1                              
II) Fritmag (%) 36.6     34.4   50.0    46.9                              
III) Filler (%) 45.0     45.0   25.0    25.0                              
2. PREFORMING                                                             
Ejectability    B        B      B       B                                 
Firmness        C        C      B       B                                 
Hardness &#34;B&#34; scale                                                        
                55       56     67      68                                
Bulk factor     3.3      3.2    3.7     3.5                               
Apparent density (g/cc)                                                   
                0.59     0.61   0.54    0.55                              
Flexural strenght (psi)                                                   
                9.0      4.8    19.2    29.9                              
3. MOLDABILITY                                                            
Sticking        A        A      A       A                                 
Blister         A        A      A       A                                 
Flow            B        B      B       B                                 
Density (g/cc)  1.95     1.98   2.00    1.95                              
Water absorption (%)                                                      
                0.37     0.18   0.15    0.14                              
Flexural strenght (psi)                                                   
                6625     7400   10200   9900                              
Shear strenght (psi)                                                      
                5625     7570    9290   9400                              
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     As can be noted, formulation nos 8 and 9 had the best preforming properties inasmuch as the firmness, ejectability and flow were all given as &#34;good&#34; (B). The flexural strengths of formulation nos 8 and 9 were equal to 10200 and 9900 psi respectively, whereas their shear strengths were equal to 9290 and 9400 psi, respectively. 
     Formulation nos 6 and 7 containing more additives and fillers than the others have shown less interesting properties. Their firmness was given as &#34;fair&#34; (C) and their ejectability and flow were both given as &#34;good&#34; (B). Their flexural strengths were equal to 6625 and 7400 psi, respectively, and their shear strengths were equal to 5625 and 7570 psi. 
     The friction characteristics of the resulting linings were measured as explained hereinabove and are reported in TABLE VIII below: 
     
                                           TABLE VII                               
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LINK-CHASE SAE J-661 FRICTION MATERIAL                                    
TEST REPORT FRITMAG FORMULATION (Example 2)                               
                  FRICTION COEFFICIENT                                    
                  No FORMULATION                                          
TEST              6     7     8     9                                     
__________________________________________________________________________
INITIAL BASELINE                                                          
APPLICATION 1     0.450 0.381 0.414 0.439                                 
       .sup.  20  0.478 0.417 0.458 0.439                                 
FIRST FADE                                                                
°F. 200    0.484 0.404 0.477 0.460                                 
   550            0.419 0.405 0.479 0.417                                 
FIRST RECOVERY                                                            
°F. 500    0.480 0.447 0.521 0.471                                 
   200            0.410 0.380 0.461 0.378                                 
WEAR                                                                      
APPLICATION 1     0.442 0.457 0.434 0.443                                 
      .sup.  100  0.355 0.369 0.411 0.401                                 
SECOND FADE                                                               
°F. 200    0.353 0.337 0.344 0.341                                 
   650            0.389 0.442 0.430 0.406                                 
SECOND RECOVERY                                                           
°F. 600    0.370 0.417 0.417 0.416                                 
   200            0.389 0.363 0.480 0.428                                 
FINAL BASELINE                                                            
APPLICATION 1     0.392 0.348 0.443 0.415                                 
       .sup.  20  0.380 0.352 0.385 0.386                                 
NORMAL COEFFICIENT                                                        
                  .sup. .sup. .sup. .sup.   0.363(F)                      
HOT FRICTION COEFFICIENT                                                  
                  .sup. .sup. .sup. .sup.   0.415(F)                      
WEAR                                                                      
WEIGHT LOSS %     7.4   5.8   8.6   6.6                                   
THICKNESS LOSS %  5.4   3.3   5.8   2.9                                   
__________________________________________________________________________
 
    
     As can be noted, formulation no. 9 had good frictional value F-F, acceptable wear rates, and good stable friction throughout the test program. Formulation nos 6, 7 and 8 also had good frictional value of F-F, acceptable wear rates, and relatively stable friction throughout the test program. 
     EXAMPLE 3 
     Using the same kind of resin and the same kinds and relative concentrations of additives and fillers as disclosed in the comparison example, six further formulations numbered 10 to 15 respectively, were prepared and processed as previously explained, using FRITMAG instead of asbestos as fibers. 
     In all of these further formulations, the ratio of resin to FRITMAG was kept constant at 0.50. However, the percentage of additives and fillers was varied (0, 15, 20, 50, 60 and 70%, respectively). 
     The preforming and mechanical properties of the resulting products are given in TABLE IX below: 
     
                                           TABLE IX                                
__________________________________________________________________________
Characteristics of the preforming material and                            
the mechanical properties of the example 3.                               
            No FORMULATION                                                
            10    11  12    13 14   15                                    
COMPOSITION RATIO (I/II)                                                  
AND PROPERTIES                                                            
            0.50  0.50                                                    
                      0.50  0.50                                          
                               0.50 0.50                                  
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1. COMPOSITION                                                            
I) Resin (%)                                                              
            33.4  28.4                                                    
                      26.7  16.7                                          
                               13.4 10.0                                  
II) Fritmag (%)                                                           
            66.6  56.6                                                    
                      53.3  33.3                                          
                               26.6 20.0                                  
III) Filler (%)                                                           
            --    15.0                                                    
                      20.0  50.0                                          
                               60.0 70.0                                  
2. PREFORMING                                                             
Ejectability                                                              
            B     B   B     B  B    B                                     
Firmness    B     B   B     B  D    D                                     
Hardness &#34;B&#34; scale                                                        
            76    72  70    55 43   33                                    
Bulk factor 4.2   3.8 3.9   2.9                                           
                               --   --                                    
Apparent density (g/cc)                                                   
            0.46  0.52                                                    
                      0.52  0.65                                          
                               0.69 0.88                                  
Flexural strenght (psi)                                                   
            36.9  26.8                                                    
                      23.7  8.4                                           
                               --   --                                    
3. MOLDABILITY                                                            
Sticking    A     A   A     A  A    --                                    
Blister     A     A   A     A  E    E                                     
Flow        B     B   B     C  C    C                                     
Density (g/cc)                                                            
            1.94  1.95                                                    
                      2.01  1.90                                          
                               --   --                                    
Water absorption (%)                                                      
            0.14  0.18                                                    
                      0.13  0.83                                          
                               --   --                                    
Flexural strenght (psi)                                                   
            13730 11775                                                   
                      10875 7475                                          
                               --   --                                    
Shear strenght (psi)                                                      
            10700  8750                                                   
                       8725 5025                                          
                               --   --                                    
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     As can be noted, formulation nos 14 and 15 containing 60% or more additives and fillers have proved to be very difficult not to say impossible to mold. 
     It is therefore obvious that the ratio of the total weight of additives and fillers to the total weight of the composition must be kept lower than 0.60. 
     The friction characteristics of linings obtained with formulation nos 10 to 13 were measured as explained hereinabove and are reported in TABLE X below: 
     
                                           TABLE X                                 
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LINK-CHASE SAE J-661 FRICTION MATERIAL                                    
TEST REPORT FRITMAG FORMULATION (Example 4)                               
                  FRICTION COEFFICIENT                                    
                  No FORMULATION                                          
TEST              10    11    12    13                                    
__________________________________________________________________________
INITIAL BASELINE                                                          
APPLICATION 1     0.347 0.312 0.261 0.446                                 
       .sup.  20  0.358 0.308 0.297 0.467                                 
FIRST FADE                                                                
°F. 200    0.385 0.350 0.307 0.349                                 
   550            0.346 0.376 0.349 0.500                                 
FIRST RECOVERY                                                            
°F. 500    0.359 0.368 0.331 0.499                                 
   200            0.425 0.345 0.361 0.468                                 
WEAR                                                                      
APPLICATION 1     0.455 0.387 0.326 0.433                                 
      .sup.  100  0.418 0.395 0.451 0.387                                 
SECOND FADE                                                               
°F. 200    0.264 0.353 0.432 0.434                                 
   650            0.322 0.371 0.421 0.405                                 
SECOND RECOVERY                                                           
°F. 600    0.277 0.425 0.459 0.401                                 
   200            0.359 0.394 0.504 0.398                                 
FINAL BASELINE                                                            
APPLICATION 1     0.524 0.430 0.473 0.405                                 
       .sup.  20  0.432 0.379 0.371 0.373                                 
NORMAL COEFFICIENT                                                        
                  .sup. .sup. .sup. .sup.   0.384(F)                      
HOT FRICTION COEFFICIENT                                                  
                  .sup. .sup. .sup. .sup.   0.380(F)                      
WEAR                                                                      
WEIGHT LOSS %     24.2  15.4  14.9  10.0                                  
THICKNESS LOSS %  21.2  12.5  12.5  10.1                                  
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     EXAMPLE 4 
     Using the same kind of resin and the same kinds and relative concentration of additives and fillers as disclosed in the comparison example, further formulations numbered 16 to 18 respectively were prepared and processed as previously explained, using FRITMAG instead of asbestos as fibers. 
     In all of these further formulations, the ratio of resin to FRITMAG was kept equal to 0.60. However the percentage of additives was varied (50, 55 and 60%, respectively). 
     The preforming and mechanical properties of the resulting products are given in TABLE XI below: 
     
                       TABLE XI                                                    
______________________________________                                    
Characteristics of the preforming material and                            
the mechanical properties of the example 3.                               
              No FORMULATION                                              
              16       17     18                                          
COMPOSITION     RATIO (I/II)                                              
AND PROPERTIES  0.60       0.60   0.60                                    
______________________________________                                    
1. COMPOSITION                                                            
I) Resin (%)    18.8       16.9   15.0                                    
II) Fritmag (%) 31.2       28.1   25.0                                    
III) Filler (%) 50.0       55.0   60.0                                    
2. PREFORMING                                                             
Ej ectability   B          B      B                                       
Firmness        C          C      D                                       
Hardness &#34;B&#34; scale                                                        
                60         55     35                                      
Bulk factor     3.1        3.5    --                                      
Apparent density (g/cc)                                                   
                0.62       0.63   0.68                                    
Flexural strenght (psi)                                                   
                6.0        --     --                                      
3. MOLDABILITY                                                            
Sticking        A          A      E                                       
Blister         A          A      E                                       
Flow            B          B      E                                       
Density (g/cc)  1.91       1.84   --                                      
Water absorption (%)                                                      
                0.30       0.53   --                                      
Flexural strenght (psi)                                                   
                6345       4785   --                                      
Shear strenght (psi)                                                      
                7285       7360   --                                      
______________________________________                                    
 
    
     As can be noted, formulations 16 and 17 have shown good preforming properties. Their firmness were given as &#34;fair&#34; (C) and their ejectability and flow were both given as &#34;good&#34; (B). Their flexural strengths were equal to 6345 and 4785 psi, respectively, and their shear strengths to 7285 and 7360 psi respectively. 
     Formulation no. 18 containing 60% of fillers and additives has proved to be very difficult to mold. 
     The friction characteristics of the linings obtained with formulation no. 16 were measured as explained hereinabove and are reported in TABLE XII below: 
     
                       TABLE XII                                                   
______________________________________                                    
LINK-CHASE SAE J-661 FRICTION MATERIAL                                    
TEST REPORT FRITMAG FORMULATION (Example 3)                               
                      FRICTION                                            
                      COEFFICIENT                                         
                      No FORMULATION                                      
TEST                  16                                                  
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INITIAL BASELINE                                                          
APPLICATION 1         0.356                                               
       .sup.  20      0.385                                               
FIRST FADE                                                                
°F. 200        0.391                                               
   550                0.413                                               
FIRST RECOVERY                                                            
°F. 500        0.437                                               
   200                0.382                                               
WEAR                                                                      
APPLICATION 1         0.405                                               
      .sup.  100      0.356                                               
SECOND FADE                                                               
°F. 200        0.361                                               
   650                0.401                                               
SECOND RECOVERY                                                           
°F. 600        0.403                                               
   200                0.365                                               
FINAL BASELINE                                                            
APPLICATION 1         0.377                                               
       .sup.  20      0.359                                               
NORMAL COEFFICIENT    .sup.   0.364(F)                                    
HOT FRICTION COEFFICIENT                                                  
                      .sup.   0.383(F)                                    
WEAR                                                                      
WEIGHT LOSS %         5.8                                                 
THICKNESS LOSS %      1.7                                                 
______________________________________                                    
 
    
     As can be noted formulation 16 had good frictional value F-F, good wear rates, but friction is a little unstable especially during the wear test.