Polymer composition
The present invention relates to polymer compositions, and the production and use of such compositions. 
     Polymeric materials are now extensively used for many purposes and in recent years polymers have become available which have high melting or softening points which make them suitable for use at higher temperatures than are attainable using the longer established polymeric materials. Polyarylether derivatives such as polyaryletherketones are examples of such polymers which, in addition to having high service temperatures have other desirable properties such as electrical insulation characteristics. Polyaryletherketones have good electrical insulating properties and high melting or softening temperatures. Some polymers of this type can be used as en electrical insulator continuously at temperatures in excess of 200° C., for example up to about 250° C. However it will be appreciated that the period of use at elevated temperature is dependent on the temperature and decreases as the temperature is increased. Although the polyaryletherketones have got properties which make them suitable for use as high temperature electrical insulators, many of these polymers have a high flexural modulus and hence may not be entirely suitable for use as a wire coating if the coated wire requires pliability. It has been found that certain additives, for example fluorinated ethylene-propylene copolymers and ethylene-tetrafluoroethylene copolymers, can improve the pliability of the polymer. However, when compositions containing these additives are used for wire coating, the coating shows reduced coherency and had a tendency to crack or even fall apart. 
     According to the present invention there is provided a polyaryletherketone composition which has a pliability which is such that a copper wire of mean diameter 1 mm, when coated with the composition to give a coating of 0.25 mm average thickness, shows a recoil, after bending through 90°, of not more than 40°. 
     Pliability is determined by bending annealed, coated wires over a 6 mm diameter mandrel. The load applied is increased until it is sufficient to bend the coated wire through 90°. The amount of recoil is measured after removing, from the coated wire, the minimum load required to bend the coated wire through 90°. For convenience hereafter, the foregoing procedure will be referred to as the &#34;recoil test&#34;. 
     We have found that the amount of recoil is influenced by the load applied in order to bend the coated wire. Accordingly, the amount of recoil is measured using the minimum load to bend the coated wire through 90°. The recoil test is effected at ambient temperature conditions, which are typically from 15° C. up to 30° C. Depending on the composition, the load required to bend the coated wire through 90° may be one kilogramme or greater. However, with some compositions in accordance with the present invention the minimum load is less than one kilogramme and may be 0.5 kilogramme or even less. Preferred compositions provide coherent coatings on the wire and are suitable for use at temperatures in excess of 200° C. for continuous periods of many weeks. 
     We have found that compositions having these properties are produced by the addition of boron nitride to the polyaryletherketone. 
     Thus, according to a further aspect of the present invention there is provided a polymer composition which comprises a mixture of a polyaryletherketone with boron nitride. 
     The composition may include other components which are suitable for incorporation into a polyaryletherketone. Such other components include, for example, inorganic and organic fibrous fillers such as glass fibre, carbon fibre and poly-paraphenylene terephthalamide fibre; organic and inorganic fillers such as polytetrafluoroethylene, graphite, mica, talc and vermiculite; and stabilisers such as phosphates. 
     It is preferred that the total proportion of additives (including boron nitride) is at least 1%, and does not exceed 70%, by weight of the composition and especially does not exceed 50% by weight of the composition. The composition preferably contains from 5 up to 30% by weight of boron nitride relative to the total weight of the composition. Compositions in accordance with the present invention include compositions consisting essentially of 70 to 95% by weight of the polyaryletherketone and correspondingly 30 to 5% by weight of boron nitride. 
     The polyaryletherketone component of the polymer composition may be a polymer which contains the repeat units ##STR1## or the repeat units ##STR2## alone or in conjunction with each other and/or in conjunction with other repeat units. 
     The other repeat units which may be present in the polyaryletherketone are typically of the general formula ##STR3## where A is a direct link, a sulphur atom, a divalent hydrocarbon radical or a group 
     
         --Q--Ar-Q.sup.1).sub.n 
    
     in which 
     Q is --CO--, --SO 2  -- or --O--; 
     Q 1  is --CO--, --SO 2  -- or --O--; 
     Ar is a divalent aromatic radical; and 
     n is 0, 1, 2 or 3. 
     In the formula III, if the group A is a divalent hydrocarbon radical it is typically a phenylene group or a dimethylmethylene group (--C(CH 3 ) 2 ). The aromatic radical Ar is preferably a divalent aromatic radical selected from phenylene, biphenylylene or terphenylylene. 
     We prefer that the polyaryletherketone is a crystalline polymer containing the repeat units I. Especially preferred are such polymers which are tough and have an inherent viscosity of at least 0.7, as is described in more detail in our European Patent Publication No. 001 879. Inherent viscosity is measured at 25° C. on a solution of the polymer in concentrated sulphuric acid of density 1.84 g cm -3 , said solution containing 0.1 g of polymer per 100 cm 3  of solution. As an alternative to inherent viscosity, an indication of the average molecular weight of the polymer may be obtained by measuring the melt viscosity of the polymer. Preferred polymers have a melt viscosity of at least 0.1 KNs/m 2 , which corresponds to an inherent viscosity of 0.7. The melt viscosity is measured using a ram extruder fitted with a 3.175 mm×0.5 mm die and operating at 400° C. and a shear rate of 1000 s -1 . 
     The boron nitride is preferably of at least 99% purity. Preferably the boron nitride is in the form of a powder of small particle size, for example having a weight average particle size of not more than 10 micrometers, particularly not more than 5 micrometers. 
     The polymer composition may be made by admixture of the two components plus any additional optional components in a suitable mixing machine to effect particle or melt blending. More specifically, the polyaryletherketone and boron nitride, in the form of dry powders or granules or mixtures thereof, can be mixed together using a suitable solids blending technique such as tumble blending or a high speed mixer. The blend thus obtained may be extruded into a lace which is chopped to give granules. The granules can be used to produce shaped articles by the use of a suitable forming operation, for example injection moulding or extrusion, to give a shaped article. 
     The shaped article obtained from the polymer composition is preferably an electrical conductor on which the polymer composition is the insulating layer or is a sheath for one or more insulated conductors. If desired, the polymer composition can be used both as the insulating layer and the outer sheath. 
     The formation of the insulating layer or outer sheath can be effected using standard wire coating conditions with the exception that the extruder is operated at a higher temperature than is usual with most plastics materials, for example at a barrel temperature of at least 340° C. and preferably with a die temperature which is at least 375° C., and which may be in excess of 400° C. 
     Wires insulated with a polymer composition of polyaryletherketone and boron nitride are more pliable than wires insulated with the polyaryletherketone only. 
     Some of the compositions of the present invention have been found to have a lower coefficient of friction and a higher limiting PV value (as defined in Notes to Table Seven) than either the polymer alone or a blend of the polymer and the same proportion by weight of poly-tetrafluoroethylene. Such a combination of properties makes the composition suitable for use in bearing applications. Thus, the polymer compositions may also be used as a bearing or as a bearing liner. 
     Thus, as a further aspect of the present invention there is provided a plain bearing formed of a polymer composition as herein described or comprising a metal backing having a lining formed of a polymer composition as herein described. 
     If the composition is used to form a plain bearing this may be done by injection moulding the composition onto the bearing. Alternatively, the composition may be extruded into the form of a rod, the centre of which is machined out to form the bearing. 
     The composition may also be used as a bearing liner on a metal backing. The metal backing may be any suitable metal such as, for example, aluminium alloy or steel with a suitable surface layer to assist in bonding the lining to the backing. The lining may be a thick coating of 0.75 to 35 mm in thickness but may be an overlay, for example of 10 to 30 micrometers, applied to a metal bearing lining. The polymer composition is preferably applied to the metal backing as a sheet. The polymer composition may be extruded to form a sheet and the sheet issuing from the extruder then bonded to the metal backing as a second stage of a single operation. Alternatively, a preformed sheet of the polymer composition is pressure bonded or roll-bonded to a heated metal backing. The temperature of bonding the polymer composition to the metal backing is preferably sufficiently high that the composition can flow under the conditions of bonding to the backing and typically the temperature is at least 350° C. The coated backing is preferably allowed to cool slowly from the temperature of bonding to ambient temperature to permit the polyaryletherketone component of the polymeric composition to attain a high crystallinity, for example at least 30%. 
     The polymer composition also has improved burning characteristics compared to the respective polymer alone. More specifically, the polymer composition has a higher oxygen index compared to the respective polymer alone. 
     The present invention is illustrated by the following examples and test results. 
    
    
     EXAMPLE 1 
     Boron nitride (obtained from Borax Consolidated Borides Division, Lake Road, Newport Industrial Estate, Gwent, NPT OSR, Great Britain) and polyetheretherketone (`Victrex` (Registered Trade Mark) PEEK aromatic polymer 450 P grade, obtainable from Imperial Chemical Industries PLC) were dry mixed by tumble blending for 15 minutes in the proportions of 15% by weight of boron nitride and 85% by weight of polyetheretherketone. 
     The blend was then formed into granules by extrusion into a lace which was cooled by passing into a water bath and the lace was then cut to form granules. The extrusion was effected using a single screw Plaston extruder having a 3.8 cm diameter screw with a length to diameter ratio of 24:1 and having the following temperature profile from the hopper end to the die 345° C., 360° C., 365° C., 370° C. and 380° C. The die was of 5 mm diameter and the extruder was operated at a rate of about 5 kg/hour. 
     EXAMPLES 2 AND 3 
     The procedure of Example 1 was repeated using different proportions of boron nitride to give compositions containing 5% by weight of boron nitride (Example 2) and 10% by weight of boron nitride (Example 3). 
     The composition of Example 1 was coated onto a 1 mm diameter copper wire using an 18 mm Bone extruder fitted with a Betol designed tubing wire coating die with total diameter of 1.5 mm. The wire was passed through the die at a rate of about 15 m/minute and the extruder was operated at a rate of about 1.6 kg/hour to give a coating of average thickness 0.25 mm. The die temperature for wire coating was about 400° C. 
     For the purposes of comparison, samples of the copper wire were also coated with the polymer (polyetheretherketone) alone. 
     The coated wires were then subjected to tests of continuous use temperature, solvent resistance and pliability and the results of these tests are set out in Tables One to Three respectively. 
     
                       TABLE ONE                                                   
______________________________________                                    
          Coating                                                         
          PEEK (a)        PEEK + BN (b)                                   
Ageing      240° C.                                                
                    300° C.                                        
                              240° C.                              
                                     300° C.                       
Time (Weeks)                                                              
            (c)     (c)       (c)    (c)                                  
______________________________________                                    
1           Pass    Pass      Pass   Pass                                 
2           Pass    Pass      Pass   Pass                                 
3           Pass    Pass      Pass   Pass                                 
4           Pass    Fail      Pass   Fail                                 
5           Pass    --        Pass   --                                   
6           Pass    --        Pass   --                                   
7           Pass    --        Pass   --                                   
8           Pass    --        Pass   --                                   
9           Pass    --        Pass   --                                   
______________________________________                                    
 Notes to Table One                                                       
 (a) PEEK indicates that the polymeric material used for coating onto the 
 wire was polyetheretherketone (`Victrex` (Registered Trade Mark), PEEK   
 aromatic polymer, 380 G grade, obtainable from Imperial Chemical         
 Industries PLC).                                                         
 (b) PEEK + BN indicates that the polymeric material used for coating onto
 the wire was the 85% by weight polyetheretherketone  15% by weight boron 
 nitride blend obtained as described in Example 1.                        
 (c) The wire samples were then tested for ID wrap failure, by wrapping th
 coated wire around itself and ageing for the time, and at the temperature
 indicated. The wire samples were examined visually periodically. Any     
 cracking observed was classed as a failure and the test was not continued
 further.                                                                 
 
    
     
                       TABLE TWO                                                   
______________________________________                                    
Coating                                                                   
Test (d)                                                                  
        PEEK (a)        PEEK + BN (b)                                     
______________________________________                                    
1 D wrap                                                                  
        One crack detected                                                
                        No cracks                                         
3 D wrap                                                                  
        Scattered cracks                                                  
                        Scattered surface cracks                          
5 D wrap                                                                  
        Cracked         Cracked                                           
14 D wrap                                                                 
        Numerous deep cracks                                              
                        Cracked, but cracks not                           
                        as large or deep as PEEK                          
______________________________________                                    
 Notes to Table Two                                                       
 (a) and (b) are as defined in Notes to Table One.                        
 (d) The coated wires were annealed at 150° C. for 24 hours in a   
 circulating air oven. The annealed, coated wires were wrapped round      
 mandrels (glass tubes) of diameter  1, 3, 5 and 14 times that of the     
 coated wire to give 1 D, 3 D, 5 D and 14 D wrap respectively. The wires  
 wrapped round the mandrels were immersed in isopropanol containing a red 
 dye for 24 hours at 70° C. The coatings were examined under a     
 microscope for cracking (shown by the dye).                              
 
    
     
                       TABLE THREE                                                 
______________________________________                                    
          Load                                                            
          applied   Recoil                                                
Coating     (kg) (e)    Degrees (f)                                       
                                  % (f)                                   
______________________________________                                    
PEEK (a)    0.6*        70        78                                      
PEEK (a)    1.0         45        50                                      
PEEK + BN (b)                                                             
            0.4*        37        41                                      
PEEK + BN (b)                                                             
            0.6         50        56                                      
PEEK + BN (b)                                                             
            1.0         25        28                                      
______________________________________                                    
 Notes to Table Three                                                     
 (a) and (b) are as defined in Notes to Table One.                        
 (e) The coated wires were annealed as described in Note (d) to Table Two.
 The annealed, coated wires were then bent through 90° over a 6 mm 
 diameter mandrel using the specified load applied. The load was then     
 removed and the amount of recoil measured.                               
 *Indicates the minimum load required to bend the coated wire through     
 (f) Recoil is measured from the 90° of arc and is expressed both i
 degrees of arc and as a percentage of 90° · (90° o
 recoil = 100% recoil)                                                    
 
    
     Injection moulded samples of the compositions of Examples 1 to 3 were subjected to limiting oxygen index, smoke density, toxic gas emission and flammability tests and also to thermo-gravimetric analysis. The results are set out in Tables Four to Six. Specimens were cut from discs 11.4 cm diameter and 3.2 mm thick, injection moulded using an injection moulding machine operating at 380° C. with a mould at about 150° C. 
     
                       TABLE FOUR                                                  
______________________________________                                    
               Limiting                                                   
               Oxygen                                                     
       Sample (h)                                                         
               Index (i)                                                  
______________________________________                                    
       PEEK    35                                                         
       1       43                                                         
       2       47                                                         
       3       45                                                         
______________________________________                                    
 Notes to Table Four                                                      
 (h) PEEK is as defined in Note (a) to Table One, with the exception that 
 Grade 450 G was used.                                                    
 1, 2, and 3, indicate the blends of the numbered Examples.               
 (i) Limiting oxygen index is measured according to ASTM Test Method      
 D286377 and is the minimum concentration of oxygen which will just suppor
 combustion of a test specimen of dimensions 6.5 (±0.5) mm × 3.0 
 (±0.5) mm × 70-150 mm cut from the injection moulded discs. Tbe 
 specimen is ignited using a hydrogen or propane flame and must burn for a
 least three minutes or for a length of at least 50 mm.                   
 
    
     
                                           TABLE FIVE                              
__________________________________________________________________________
Smoke test (j)                                                            
Minimum    Time to      Gas analysis (k)                                  
      trans                                                               
           minimum  Weight                                                
                        CO  CO.sub.2                                      
                               SO.sub.2                                   
                                   HCN                                    
Sample (h)                                                                
      %    trans (min)                                                    
                 D.sub.m                                                  
                    loss %                                                
                        (ppm)                                             
                            (%)                                           
                               (ppm)                                      
                                   (ppm)                                  
__________________________________________________________________________
PEEK  91   20    5  1.5 240 0  ND  ND                                     
1     95.5 37    2.5                                                      
                    0.55                                                  
                        170 0  ND  ND                                     
2     95   20    3  0.8 150 0  ND  ND                                     
3     97   20    2  0.4 150 0  ND  ND                                     
__________________________________________________________________________
 Notes to Table Five                                                      
 (h) is as defined in Notes to Table Four.                                
 (j) Smoke density test was carried out in a NBS smoke chamber using the  
 procedure of ASTM Test Method E66279. The test specimens were 76 × 
 76 mm × 3.0 (±0.5) mm, (cut from the injection moulded discs) an
 were mounted in a holder to expose an area about 65 × 65 mm. The   
 test was carried out in the flaming mode and the smoke density was       
 determined by passing a collimated light beam (from an incandescent light
 source) vertically through the smoke chamber to a photodetector.         
 D.sub.m is the Maximum specific optical density.                         
 (k) After exposure of the sample in the smoke chamber for 20 minutes, gas
 samples were taken using Drager tubes and the samples were analysed. The 
 results for CO and CO.sub.2 include a correction for the quantities of   
 these gases emitted by the gas jets.                                     
 
    
     ND means that the proportions of these gases were below the lower limits of detection of the test, that is &lt;1 ppm of SO 2  and &lt;2 ppm of HCN. 
     Examination of the PEEK+BN sample of Example 1 which had been exposed in the NBS smoke chamber for 20 minutes showed a pronounced intumescent effect and a hard char. 
     
                       TABLE SIX                                                   
______________________________________                                    
         Burning test (l)                                                 
                 Mean Burn time                                           
                       1st ignition                                       
                                  2nd ignition                            
Sample (h) Classification                                                 
                       (sec)      (sec)                                   
______________________________________                                    
PEEK       94V-0       0          2                                       
1          94V-0       0          0.6                                     
2          94V-0       0          0                                       
3          94V-0       0          0                                       
______________________________________                                    
 Notes to Table Six                                                       
 (h) is as defined in Notes to Table Four.                                
 (l) Flammability was tested using the Underwriter&#39;s Laboratories UL94    
 vertical test. The test specimens were about 110 × 12.7 mm area and
 cut from the injection moulded discs. Each specimen was clamped in a     
 draught free cabinet and ignited by applying a blue bunsen burner flame  
 for 10 seconds. The time taken for the flame to go out was recorded after
 a first and a second ignition.                                           
 
    
     A quantity of granules obtained by Example 1 was subjected to thermo-gravimetric analysis between 200° and 500° C. using a temperature rise of 5° C. per minute. The total weight loss from the polyetheretherketone/boron nitride composition produced by the process of Example 1 was about 2% up to a temperature of about 520° C. (PEEK shows a total weight loss of about 3% under the same test conditions). 
     Test specimens of about 10 mm×10 mm×3.0(±0.5) mm in size, cut from the injection moulded discs, were subjected to tribilogical testing. The test results are set out in Tables Seven and Eight. 
     
                                           TABLE SEVEN                             
__________________________________________________________________________
         Ambient Temperature                                              
                           200° C.                                 
                     Wear              Wear                               
         Load        Rate  Load        Rate                               
Sample   (kg)                                                             
             LPV CF  (n)   (kg)                                           
                               LPV CF  (n)                                
(h) (m)  (n) (o)                                                          
             (n) (p)                                                      
                 (n) (q)                                                  
                     (r)                                                  
                        (s)                                               
                           (n) (o)                                        
                               (n) (p)                                    
                                   (n) (q)                                
                                       (r)                                
                                          (s)                             
__________________________________________________________________________
PEEK      70 3640                                                         
                 0.42                                                     
                     303                                                  
                        432                                               
                            70 4010                                       
                                   0.2 350                                
                                          300                             
PEEK + PTFE                                                               
         140 7115                                                         
                 0.12                                                     
                     250                                                  
                        250                                               
                           150 7030                                       
                                   0.11                                   
                                       250                                
                                          458                             
1        200 10310                                                        
                 0.06                                                     
                     408                                                  
                        413                                               
                           210 9815                                       
                                   0.05                                   
                                       127                                
                                          279                             
__________________________________________________________________________
Notes to Table Seven                                                      
(h) is as defined to Notes to Table Four                                  
(m) PEEK + PTFE is a composition of polyetheretherketone (Victrex` PEEK   
aromatic polymer, 450                                                     
G grade) and polytetrafluoroethylene (`Fluon` (Registered Trade Mark)     
L169 lubricant grade polytetrta                                           
fluoroethylene powder) containing 15% by weight of polytetrafluoroethylene
 and obtained by a                                                        
method as described for the production of PEEK + BN in Example 1.         
(n) Tribilogical data was obtained using an Amsler Wear Test Machine      
operating in a pad on ring con-                                           
fiuration. The pads were the test specimens of 10 mm × 10 mm        
× 3.0 (±0.5) mm described pre-                                   
viously. The ring was 60 mm in diameter and 6mm wide and was formed of    
EN8 steel ground to a sur-                                                
face finish of 0.3 to 0.4 micrometers Ra. The ring was rotated to give a  
surface speed of 100 feet/                                                
minute (30.48 meters/minute). The test specimen was &#34;run in&#34; for 10       
minutes under a 10 kg load                                                
and for a further 10 minutes under a 30 kg load. The load was then        
increased in increments of 20-30                                          
kg and each load was maintained for 0.5 hour. The load was increased up   
to a maximum of 210 kg or                                                 
until one of the failure criteria was exceeded. The failure criteria are  
catastrophic (that is rapid) in-                                          
crease in wear, friction or temperature. Tests were carried out at        
ambient temperature and                                                   
at 200° C.                                                         
(o) Maximum test load reached before failure.                             
(p) Limiting value of PV (Pressure X Velocity) is calculated by dividing  
load (in kg) by actual area of                                            
contact (wear scar area in cm.sup.2) and multiplying result by surface    
speed (in m/minute).                                                      
(q) CF is the coefficient of friction and is the average of the           
coefficient of friction at the load giving                                
the limiting value of PV and the coefficient of friction at half the load 
which gives the limiting value                                            
of PV. The coefficient of friction was measured continuously.             
(r) Wear rate up to half the load which gives the limiting value of PV.   
(s) Wear rate up to the load which gives the limiting value of PV.        
 
    
     
                                           TABLE EIGHT                             
__________________________________________________________________________
         Ambient temperature                                              
                           200° C.                                 
                     Wear              Wear                               
         Load        Bate  Load        Rate                               
Sample   (kg)                                                             
             LPV CF  (t)   (kg)                                           
                               LPV CF  (t)                                
(h) (m)  (o) (t)                                                          
             (p) (t)                                                      
                 (q) (t)                                                  
                     (r)                                                  
                        (s)                                               
                           (o) (t)                                        
                               (p) (t)                                    
                                   (q) (t)                                
                                       (r)                                
                                          (s)                             
__________________________________________________________________________
PEEK      8  1480                                                         
                 0.58                                                     
                     450                                                  
                        ND  8  1500                                       
                                   0.51                                   
                                       150                                
                                          300                             
PEEK + PTFE                                                               
         20  3645                                                         
                 0.28                                                     
                     600                                                  
                        138                                               
                           12  2270                                       
                                   0.27                                   
                                       ND 180                             
1        40  6085                                                         
                 0.07                                                     
                     330                                                  
                        247                                               
                           20  6580                                       
                                   0.05                                   
                                        51                                
                                          119                             
__________________________________________________________________________
 Notes to Table Eight                                                     
 (h) is as defined in Notes to Table Four.                                
 (m) to (s) are all as defined in Notes to Table Seven.                   
 (t) Tribilogical data was obtained essentially as described in Note (n) t
 Table Seven with the exception that the ring was rotated to give a surfac
 speed of 600 feet/minute (182.9 meters/minute) and the test specimen was 
 `run in`  differently. The test specimen was `run in` for 10 minutes unde
 a 3 kg load and for a further 10 minute under 5 kg load. The load was    
 increased in 5 kg increments to a maximum of 40 kg.                      
 
    
     The compositions of Examples 2 and 3 were coated onto 1 mm diameter copper wire in the manner described previously in respect of the composition of Example 1. For the purposes of comparison, the copper wire was also coated with different grade of the polymer (polyetheretherketone) alone. 
     The tests described previously and reported in Tables One to Three were repeated and the results of these additional tests are set out in Tables Nine to Eleven. 
     
                       TABLE NINE                                                  
______________________________________                                    
Coating                                                                   
Aging  PEEK (u)     2 (u)        3 (u)                                    
Time   240° C.                                                     
               300° C.                                             
                        240° C.                                    
                              300° C.                              
                                     240° C.                       
                                           300° C.                 
(Weeks)                                                                   
       (c)     (c)      (c)   (c)    (c)   (c)                            
______________________________________                                    
1      Pass    Pass     Pass  Pass   Pass  Fail                           
2      Pass    Fail     Pass  Fail   Pass  --                             
3      Pass    --       Pass  --     Pass  --                             
4      Pass    --       Pass  --     Pass  --                             
5      Pass    --       Pass  --     Pass  --                             
______________________________________                                    
 Notes to Table Nine                                                      
 (c) is as defined in Notes to Table One.                                 
 (u) PEEK is as defined in Note (a) to Table One with the exception that  
 Grade 450 G was used.                                                    
 2 and 3 indicate the blends of the numbered Examples.                    
 
    
     
                       TABLE TEN                                                   
______________________________________                                    
Coating                                                                   
Test (d)   PEEK (u)    2 (u)     3 (u)                                    
______________________________________                                    
1 D Wrap   No cracks   No cracks No cracks                                
3 D Wraps  No cracks   No cracks No cracks                                
5 D Wraps  No cracks   No cracks No cracks                                
14 D Wraps No cracks   No cracks No cracks                                
______________________________________                                    
 Notes to Table Ten                                                       
 (d) is as defined in Notes to Table Two.                                 
 (u) is as defined in Notes to Table Nine.                                
 
    
     
                       TABLE ELEVEN                                                
______________________________________                                    
        Load Applied                                                      
                    Recoil                                                
Coating (u)                                                               
          (kg) (e)      Degrees (f)                                       
                                  % (f)                                   
______________________________________                                    
PEEK      1.0*          47        52                                      
2         1.0*          35        39                                      
3         1.0*          39.5      44                                      
______________________________________                                    
 Notes to Table Eleven                                                    
 (e) and (f) are as defined in Notes to Table Three.                      
 (u) is as defined in Notes to Table Nine.