SILICONE ELASTOMER COMPOSITIONS AND ELASTOMERIC MATERIALS

Abstract

Provided herein is a self-lubricating silicone elastomer composition and a self-lubricating, elastomeric material made therefrom which has a low coefficient of friction and avoids the need for “self-bleeding”. The self-lubricating silicone elastomer composition comprises: (i) 50 to 75% by weight of one or more polydiorganosiloxane polymer(s) containing from 0.01 to 0.1% by weight of alkenyl and/or alkynyl content; (ii) 3 to 15% by weight of a polydiorganosiloxane polymer having ≥0.5% by weight of alkenyl or alkynyl content; (iii) 10 to 35% by weight of reinforcing filler; and either or both of (iv) a peroxide catalyst; or (v) a hydrosilylation catalyst package.

Claims

1. A self-lubricating silicone elastomer composition comprising: (i) 50 to 75% by weight of one or more polydiorganosiloxane polymer(s) containing from 0.01 to 0.1% by weight of alkenyl and/or alkynyl content; (ii) 3 to 15% by weight of a polydiorganosiloxane polymer having ≥0.5% by weight of alkenyl or alkynyl content; (iii) 10 to 35% by weight of reinforcing filler; and either (iv) a peroxide catalyst; or (v) a hydrosilylation catalyst package comprising (a) a polydiorganosiloxane polymer having at least 2, alternatively at least 3 Si—H groups per molecule; and (b) a hydrosilylation catalyst; or (vi) a combination of (iv) and (v).

2. The self-lubricating silicone elastomer composition in accordance with claim 1, wherein components (i) and (ii) comprise silicone gums having a Williams plasticity of >30 mm/100 in accordance with ASTM D-926-08.

3. The self-lubricating silicone elastomer composition in accordance with claim 1, wherein components (i) and (ii) comprise fluorosilicone gums having a Williams plasticity of >30 mm/100 in accordance with ASTM D-926-08.

4. The self-lubricating silicone elastomer composition in accordance with claim 1, wherein components (i) and (ii) comprise fluorosilicone gums, the composition is hydrosilylation curable, and the polydiorganosiloxane polymer (v)(a) is fluoro containing.

5. The self-lubricating silicone elastomer composition in accordance with claim 1, wherein the reinforcing filler (iii) is a treated fumed silica, precipitated silica, silica aerogel or a mixture thereof.

6. The self-lubricating silicone elastomer composition in accordance with claim 1, werein when component (v) is present there is additionally optionally provided a hydrosilylation cure inhibitor in an amount of from 0 to 1% by weight of the composition.

7. The self-lubricating silicone elastomer composition in accordance with claim 1, wherein when component (v) is present, the composition is stored in two parts, a first part, Part A, comprising components (i), (iii) and (v)(b) and a second part, Part B, which comprises components (i), (iii), and (v)(a), and wherein component (ii) is present in Part A, or Part B, or divided between Part A and Part B.

8. The self-lubricating silicone elastomer composition in accordance with claim 1, additionally comprising polytetrafluoroethylene having a particle size of from 250 to 750 μm.

9. The self-lubricating silicone elastomer composition in accordance with claim 8, comprising polytetrafluoroethylene having a particle size of from 350 to 550 μm,

10. The self-lubricating silicone elastomer composition in accordance with claim 1, which is non-oil bleeding and/or non-oil filled.

11. The self-lubricating silicone elastomer composition in accordance with claim 1, further comprising one or more of compatibilising agents, electrical and thermally conductive fillers, non-conductive fillers, pot life extenders, flame retardants, non-reinforcing fillers, pigments, coloring agents, adhesion promoters, chain extenders, silicone polyethers, and mixtures thereof.

12. A self-lubricating silicone elastomeric material which is the cured product of the composition in accordance with claim 1.

13. The self-lubricating silicone elastomeric material in accordance with claim 12, having a post cured kinetic coefficient of friction of >0 and ≤0.8 or having a post cured kinetic coefficient of friction of >0 and ≤1.25 in the case of a fluorosilicone elastomeric material.

14. The self-lubricating silicone elastomeric material in accordance with claim 12, adapted for use in straps and bands of wearable devices, protection covers for mobile phones and other personal electronic devices, catheters, gaskets and/or seals for healthcare applications, wiper blades, connector seals, matt seals, wire seals kitchenware, sanitation articles, insulators and/or arresters for high voltage industry.

15. A device selected from straps and bands of wearable devices, protection covers for mobile phones and other personal electronic devices, catheters, gaskets and/or seals for healthcare applications, wiper blades, connector seals, matt seals, wire seals kitchenware, sanitation articles, insulators and/or arresters for high voltage industry, which consists or comprises of the self-lubricating silicone rubber elastomer material in accordance with claim 12.

16. A method of manufacturing a self-lubricating silicone elastomeric material, comprising mixing the components of the self-lubricating silicone elastomer composition in accordance with claim 1 and curing the composition.

17. (canceled)

18. (canceled)

Description

EXAMPLES

[0107] A series of comparative examples (C.1-C.2) and examples (Ex.1-Ex.11) supporting the present disclosure were prepared by mixing all the components specified in Tables 1a, 1c and 1e. components (i) and (ii) in these examples were silicone gums (non-fluoro containing). Unless otherwise indicated Williams plasticity for each gum was determined in accordance with ASTM D-926-08. All viscosities were measured at 25° C. relying on the cup/spindle method of ASTM D 1084 Method B, with the most appropriate spindle from the Brookfield® RV or LV range for the viscosity range, unless otherwise indicated. The alkenyl and/or alkynyl and/or silicon bonded hydrogen (Si—H) content of the components was determined using quantitative infra-red analysis in accordance with ASTM E168. Some of the compositions comprise amounts of polytetrafluoroethylene (PTFE). Standard PTFE in the following Tables refer to powdered PTFE having an average particle size (provided by supplier) of about 10 μm. LPS PTFE in the following Table is intended to identify large particle sized PTFE having an average particle size of between 400 and 500 μm.

[0108] Coefficient of friction values and other physical property results for the respective compositions/elastomers are shown, together with the test methods used, in Tables 1 b, 1 d and 1f. The static and kinetic coefficient of friction measurements were made using a Labthink MXD-02 machine in accordance with test method (GB/T 10006-1988). These tables provide evidence that compositions as hereinbefore described using gums as polymers (i) and (ii) fall within the scope of this disclosure.

TABLE-US-00001 TABLE 1a Compositions of Gum Comparatives and Examples Components C. 1 Ex. 1 C. 2 Ex. 2 Ex. 3 Dimethylvinyl terminated dimethyl methylvinyl polysiloxane 36.114 31.414 gum having a Williams plasticity 155 mm/100 and a vinyl content of 0.065 wt. % Dimethylvinyl terminated dimethyl polysiloxane gum having 36.114 31.414 64.696 63.124 55.436 a Williams plasticity of 154 mm/100, and a vinyl content of 0.014 wt. % Dimethylvinyl terminated dimethyl methylvinyl polysiloxane 9.180 8.551 gum - Williams plasticity of 135 mm/100 and a vinyl content of 0.7 wt. % Dimethylvinyl terminated dimethyl methylvinyl polysiloxane, 1.941 1.894 1.663 having a viscosity of 150,000 mPa .Math. s and a vinyl content of 7.7 wt. % trimethyl terminated dimethyl methylhydrogen polysiloxane, 0.508 0.441 3.337 having a viscosity of 5 mPa .Math. s and an Si—H content of 0.776 wt. % Treated fumed silica 26.784 26.052 32.883 32.405 28.458 LPS PTFE powder 1.040 2.104 2.086 DMBPH (2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane) 0.480 0.459 0.480 0.473 0.469

[0109] The filler(s) and filler treating agent(s) were first mixed with and evenly dispersed into the gum(s) to form a silicone rubber base. The remaining components were then added and dispersed into the base and the final compositions were press cured for 10 minutes at a temperature of 170° C. Some samples were post cured for 4 hours at 200° C. in order to compare coefficient of friction values between non-post cure samples and post cure samples.

TABLE-US-00002 TABLE 1b Physical Properties of Elastomers made from Compositions of Table 1a Property C. 1 Ex. 1 C. 2 Ex. 2 Ex. 3 Non-Post Cure Durometer, Shore A, points (ASTM D2240) 50 46 48 55 52 Tensile strength (MPa) (ASTM D412) 9.9 9.8 8.2 8.3 8.4 Elongation at break, % (ASTM D412) 574 750 703 729 833 Tear strength, kN/m (ASTM D624 Die B) 23.3 32.1 32.4 32.3 39.6 Specific gravity (ASTM D792) 1.144 1.143 1.162 1.178 1.153 Static CoF (GB/T 10006-1988) 0.540 0.406 0.574 0.531 0.566 Kinetic CoF (GB/T 10006-1988) 1.012 0.439 1.478 0.799 0.604 After post cure Durometer, Shore A, points (ASTM D2240) 54 51 51 57 55 Tensile strength (MPa) (ASTM D412) 9.0 8.9 10.7 9.2 7.9 Elongation at break, % (ASTM D412) 455 535 734 730 757 Tear strength, kN/m (ASTM D624 Die B) 16.6 20.6 37.0 36.2 43.7 Specific gravity (ASTM D792) 1.144 1.145 1.174 1.184 1.160 Static CoF (GB/T 10006-1988) 0.540 0.537 0.495 0.512 0.557 Kinetic CoF (GB/T 10006-1988) 1.042 0.753 0.999 0.775 0.652

[0110] It can be seen when comparing comparative composition 1 (C.1) and Example 1 (Ex.1) that the latter shows a much reduced kinetic coefficient of friction showing the difference of only using polymer (i) and both polymer (i) and (ii) with a peroxide cure system and a small amount of LPS PTFE powder, respectively. Comparing C 2 with Ex.2 and Ex.3 it can be seen that the addition of LPS PTFE powder causes a reduction in combination with polymer (i) alone but results show further improvement in the presence of component (ii) as well as the LPS PTFE powder.

[0111] Examples in accordance with the disclosure herein were likewise prepared and cured from compositions depicted in Table 1c below.

TABLE-US-00003 TABLE 1c Compositions of Gum Examples Components Ex. 4 Ex. 5 Ex. 6 Ex. 7 Dimethylvinyl terminated dimethyl 60.009 59.397 59.397 58.795 polysiloxane gum having a Williams plasticity of 154 mm/100, and a vinyl content of 0.014 wt. % Dimethylvinyl terminated dimethyl 8.484 8.397 8.397 8.312 methylvinyl polysiloxane gum - Williams plasticity of 135 mm/100 and a vinyl content of 0.7 wt. % trimethyl terminated dimethyl 3.311 3.277 3.277 3.244 methylhydrogen polysiloxane, having a viscosity of 5 mPa .Math. s and an Si—H content of 0.776 wt. % Treated fumed silica 27.730 27.444 27.444 27.166 Standard PTFE 1.024 LPS PTFE powder 1.024 2.027 DMBPH (2,5-Dimethyl-2,5-di(tert- 0.466 0.461 0.461 0.456 butylperoxy)hexane)

[0112] Physical properties of the resulting elastomers were determined and are depicted in Table 1d below.

TABLE-US-00004 TABLE 1d Physical Properties of Elastomers made from Compositions of Table 1c Property Ex. 4 Ex. 5 Ex. 6 Ex. 7 Non-Post Cure Durometer, Shore A, points (ASTM D2240) 60 61 62 65 Tensile strength (MPa) (ASTM D412) 10.5 10.4 9.2 9.3 Elongation at break, % (ASTM D412) 634 589 637 610 Tear strength, kN/m (ASTM D624 Die B) 49.4 48.2 48.7 51.6 Specific gravity (ASTM D792) 1.147 1.149 1.148 1.16 Static CoF (GB/T 10006-1988) 0.523 0.535 0.452 0.532 Kinetic CoF (GB/T 10006-1988) 0.764 0.801 0.462 0.511 After post cure Durometer, Shore A, points (ASTM D2240) 61 62 63 65 Tensile strength (MPa) (ASTM D412) 10.3 10.2 9.0 9.2 Elongation at break, % (ASTM D412) 604 570 603 534 Tear strength, kN/m (ASTM D624 Die B) 49.7 48.8 43.0 51.8 Specific gravity (ASTM D792) 1.155 1.157 1.157 1.16 Static CoF (GB/T 10006-1988) 0.519 0.511 0.466 0.356 Kinetic CoF (GB/T 10006-1988) 0.719 0.701 0.492 0.305

[0113] Comparisons of E4 and E5 with Ex. 6 and 7 show that the coefficient of friction results are further improved by the addition of PTFE, in particular the LPS PTFE powder.

[0114] Further examples in accordance with the disclosure herein were likewise prepared and cured from compositions depicted in Table 1e below.

TABLE-US-00005 TABLE 1e Compositions of Gum Examples Components Ex. 8 Ex. 9 Ex. 10 Ex. 11 Dimethylvinyl terminated dimethyl polysiloxane 60.2861 59.0579 58.4650 59.6677 gum havinga Williams plasticity of 154 mm/100 and a vinyl content of 0.014 wt. % Dimethylvinyl terminated dimethyl methylvinyl 8.5234 8.3499 8.2652 8.4353 polysiloxane gum havinga Williams plasticity of 135 mm/100 and a vinyl content of 0.7 wt. % Dimethylvinyl terminated dimethyl methylvinyl polysiloxane havinga viscosity of 150,000 mPa .Math. s, and a vinyl content of 7.7 wt. % trimethyl terminated dimethyl methylhydrogen 3.3262 3.2585 3.2255 3.2918 polysiloxane havinga viscosity of viscosity5 mPa .Math. s and an Si—H content of 0.776 wt. % Treated fumed silica 27.8569 27.2899 27.0132 27.5692 LPS PTFE powder 2.0366 3.0239 1.0287 1,3-Dietheny1-1,1,3,3-Tetramethyldisiloxane 0.0004 0.0004 0.0004 0.0004 Complexes (Platinum) Ethynyl-1-cyclohexanol (ETCH) 0.0070 0.0068 0.0068 0.0069

[0115] Physical properties of the resulting elastomers were determined and are depicted in Table 1f below.

TABLE-US-00006 TABLE 1f Physical Properties of Elastomers made from Compositions of Table 1e Property Ex. 8 Ex. 9 Ex. 10 Ex. 11 Non-Post Cure Durometer, Shore A, points (ASTM D2240) 46 51 56 50 Tensile strength (MPa) (ASTM D412) 5.1 4.0 3.7 3.7 Elongation at break, % (ASTM D412) 854 855 806 696 Tear strength, kN/m (ASTM D624 Die B) 30.4 31 33.2 27.4 Specific gravity (ASTM D792) 1.15 1.16 1.16 1.15 Static CoF (GB/T 10006-1988) 0.29 0.343 0.338 0.489 Kinetic CoF (GB/T 10006-1988) 0.286 0.315 0.357 0.37 After post-cure Durometer, Shore A, points (ASTM D2240) 60 63 67 62 Tensile strength (MPa) (ASTM D412) 7.4 7.1 7.1 8.1 Elongation at break, % (ASTM D412) 775 678 704 781 Tear strength, kN/m (ASTM D624 Die B) 48.4 40.9 43.3 43.5 Specific gravity (ASTM D792) 1.15 1.16 1.17 1.16 Static CoF (GB/T 10006-1988) 0.36 0.221 0.181 0.231 Kinetic CoF (GB/T 10006-1988) 0.357 0.243 0.175 0.241

[0116] E8˜E11 show the synergetic effect identified herein between special construct of the polymers with hydrosilylation cure system and the added LPS PTFE powder in reducing CoF.

[0117] It can be seen that generally the kinetic coefficient of friction results are quite significantly lower than comparatives in Tables 1a/1b. Of particular note is that the peroxide curing agent used in previous examples had been replaced by a component (v) addition cure package and the coefficient of friction results were even lower using said package to cure the elastomer.

[0118] A series of fluorinated organopolysiloxane composition were prepared in accordance with the disclosure. The composition utilised are depicted in Table 2a and 2c and the respective physical properties are depicted in Tables 2b and 2d below.

TABLE-US-00007 TABLE 2a Compositions of Fluorosilicone Comparatives and Examples Components C. 3 C. 4 C. 5 Ex. 12 Dimethylhydroxy trifluoropropylmethyl Siloxane 59.715 gum having a Williams plasticity of 299 mm/100 Dimethylhydroxy terminated methylvinyl, 12.827 67.754 13.432 trifluoropropylmethyl Siloxane gum having a Williams plasticity of 284 mm/100, and a vinyl content of 0.0996 wt. % Dimethylhydroxy terminated methylvinyl, 3.803 trifluoropropylmethyl Siloxane gum - having a Williams plasticity of 330 mm/100, and a vinyl content of 1.37 wt. % Dimethylhydroxy terminated 57.693 trifluoropropylmethyl Siloxane gum having a Williams plasticity of 330 mm/100, Dimethylhydroxy terminated methylvinyl, 65.206 trifluoropropylmethyl Siloxane gum having a Williams plasticity of 284 mm/100, and a vinyl content of 0.0996 wt. % Trimethyl terminated 2.425 dimethylmethylhydrogensiloxane having a viscosity of 15 mPa .Math. s and an Si—H content of 0.838 wt. % LPS PTFE powder 1.987 2.030 1.941 Treated Fumed silica 29.016 29.812 24.366 26.188 DMBPH (2,5-Dimethyl-2,5-di(tert- 0.464 0.447 0.457 butylperoxy)hexane) DCBP (Bis(2,4-Dichloro Benzoyl) Peroxide) 0.437

[0119] Physical properties of the resulting elastomers were determined and are depicted in Table 2b below. Physical properties were measured using the same methods as described above and/or indicated in the Table below.

TABLE-US-00008 TABLE 2b Physical Properties of Elastomers made from Compositions of Table 2a Property C. 3 C. 4 C. 5 Ex. 12 Non-Post Cure Static CoF (GB/T 10006-1988) 0.59 0.56 0.53 0.56 Kinetic CoF (GB/T 10006-1988) 1.71 1.64 1.71 0.73 After Post Cure Durometer, Shore A, points (ASTM D2240) 57 50 45 50 Tensile strength (MPa) (ASTM D412) 9.4 8.1 6.2 7.7 Elongation at break, % (ASTM D412) 310 436 369 421 Tear strength, kN/m (ASTM D624 15.7 42.7 18.2 25.8 Die B) Specific gravity (ASTM D792) 1.430 1.459 1.440 1.424 Static CoF post (GB/T 10006-1988) 0.59 0.55 0.55 0.57 Kinetic CoF post (GB/T 10006-1988) 1.76 1.50 1.51 1.00

[0120] Again it can be seen that the kinetic coefficient of friction of example 12 give much lower results than do the comparatives in the above table.

[0121] A further series of fluorinated organopolysiloxane composition were prepared in accordance with the disclosure and are depicted in Table 2c below.

TABLE-US-00009 TABLE 2c Compositions of Fluorosilicone Comparatives and Examples Component Ex. 13 Ex. 14 C. 6 Ex. 15 Ex. 16 Dimethylhydroxy terminated methylvinyl, trifluoropropylmethyl Siloxane gum having a Williams plasticity of 284 mm/100, and a vinyl content of 0.0996 wt. % Dimethylhydroxy terminated 3.803 3.9953 3.9954 3.898 3.5639 methylvinyl, trifluoropropylmethyl Siloxane gum - having a Williams plasticity of 330 mm/100, and a vinyl content of 1.37 wt. % Dimethylhydroxy terminated 65.206 66.0290 66.9557 64.419 61.0980 methylvinyl, trifluoropropylmethyl Siloxane gum having a Williams plasticity of 284 mm/100, and a vinyl content of 0.0996 wt. % Trimethyl terminated 2.425 dimethylmethylhydrogensiloxane having a viscosity of 15 mPa .Math. s and an Si—H content of 0.838 wt. % LPS PTFE powder 1.941 1.989 1.9759 Treated Fumed silica 26.188 27.5087 27.5093 26.840 25.5130 DMBPH (2,5-Dimethyl-2,5-di(tert- 0.437 0.447 0.4446 butylperoxy)hexane) 1,3-Dietheny1-1,1,3,3 - 0.0005 0.0005 0.0027 Tetramethyldisiloxane Complexes (Platinum) Dimethylhydrogensiloxy-terminated 2.4665 2.407 2.4622 Trifluoropropyl Silsesquioxane Dimethylhydrogensiloxy-Modified 1.5391 Silica Trimethyl terminated polydimethylsiloxane 4.9397 viscosity 100 mPa .Math. s

[0122] Physical properties of the resulting elastomers were determined and are depicted in Table 2d below.

TABLE-US-00010 Table 2d Physical Properties of Elastomers made from Compositions of Table 2c Property Ex. 13 Ex. 14 C. 6 Ex. 15 Ex. 16 Non-Post Cure Static CoF non-post (GB/T 10006-1988) 0.48 0.56 0.57 0.56 0.25 Kinetic CoF non-post (GB/T 10006-1988) 0.66 1.52 1.41 0.83 0.29 After post cure Durometer, Shore A, points (ASTM D2240) 70 59 52 63 67 Tensile strength (MPa) (ASTM D412) 7.3 9.6 6.7 9.4 6.1 Elongation at break, % (ASTM D412) 191 426 559 350 192 Tear strength, kN/m (ASTM D624 Die B) 15.2 36.7 29.3 34.7 22.4 Specific gravity (ASTM D792) 1.427 NA NA 1.434 1.395 Static CoF post (GB/T 10006-1988) 0.57 0.55 0.56 0.49 0.20 Kinetic CoF post (GB/T 10006-1988) 1.20 0.91 1.36 0.80 0.22

[0123] Comparing in particular C3˜C5 and E12 from Table 2b and E13 in Tables 2c and d, it will be appreciated that a synergistic effect is evident not only when the Component (ii) is present but this is enhanced in combination with LPS PTFE powder. Again it can be seen that the kinetic coefficient of friction of the compositions in accordance with the disclosure give much lower results than do the comparatives in the above table.

Comparing between E15˜16 and C6 and it can be seen that it is advantageous to utilise a fluoro containing cross-linker for fluorosilicone examples provided above. Again, it can also be seen that the CoF values are improved by the addition of LPS PTFE powder especially for Ex. 16 but that in the case of Ex. 14 very good results are achieved in the absence of ptfe.

[0124] A series of liquid silicone rubber (LSR) compositions in accordance with the enclosed was also prepared and are depicted in Table 3a and 3b below. Table 3a depicts two masterbatches prepared for use in the 2-part LSR compositions described in Table 3b.

TABLE-US-00011 TABLE 3a Masterbatch bases for LSR composition MB 1 MB 2 (wt. %) (wt. %) Dimethylvinyl terminated dimethyl Siloxane 62.14 50.82 having a viscosity of 55,000 mPa .Math. s and a vinyl content of 0.09 wt. % Dimethylvinyl terminated dimethyl methylvinyl 8.00 Siloxane having a viscosity of 12967 mPa .Math. s and a vinyl content of 7.71 wt. % treated fumed silica 37.86 41.18 having a BET surface area of about 300 m.sup.2/g Total 100 100

[0125] Compositions were prepared and stored in two parts (Part A and Part B) to avoid premature cure. In the case of both C.7 and Ex. 17a platinum catalyst was incorporated in the part A composition and an Si—H containing cross-linker and inhibitor were both present in the Part B composition. The two parts were mixed in a 1:1 ratio immediately before application and cure. The composition was cured at a temperature of 150° C. for 5 minutes and for some samples are post cured for 4 hours at 200° C.

TABLE-US-00012 Table 3b Compositions of LSR Comparative and Example C. 7 C. 7 Ex. 17 Ex. 17 Components Part A Part B Part A Part B MB 1 85.89 82.09 MB 2 83.67 86.49 Dimethylvinyl terminated dimethyl Siloxane having a viscosity 8.15 7.25 4.75 of 55,000 mPa .Math. s and a vinyl content of 0.09 wt. % Dimethyl, Methylvinyl Siloxane, Dimethylvinylsiloxy- 6.02 4.51 11.42 0.00 terminated 350 mPa .Math. s and a vinyl content of 1.15 wt. % Platinum catalyst 0.20 0.16 Ethynyl-1-cyclohexanol (ETCH) in 1.60 2.42 Dimethylvinylsiloxy-terminated Dimethyl, Methylvinyl Siloxane, 350 mPa .Math. s and a vinyl content of 1.15 wt. % Tetramethyltetravinylcyclotetrasiloxane 0.14 Trimethylsiloxy-terminated Dimethyl, 4.55 0 7.79 Methylhydrogen Siloxane having a viscosity of 48 mPa .Math. s and an Si—H content of 0.72 wt. % Trimethylsiloxy terminated methylhydrogen Siloxane, 0 3.30 viscosity 30 mPa .Math. s and an Si—H content of 1.57% Total dosage 100.00 100.00 100.00 100.00

[0126] Physical properties of the resulting elastomers were determined and are depicted in Table 3c below.

TABLE-US-00013 TABLE 3c Physical Properties of Elastomers made from Compositions of Table 2c Property C. 7 Ex. 17 Press cure 150° C. for 5 min Durometer, Shore A, points (ASTM D2240) 58 83 Tensile strength (MPa) (ASTM D412) 10.5 7.11 Elongation at break, % (ASTM D412) 464 123 Tear strength, kN/m (ASTM D624 Die B) 38.8 8.2 Specific gravity (ASTM D792) 1.123 1.152 Static CoF (GB/T 10006-1988) 0.553 0.354 Kinetic CoF (GB/T 10006-1988) 1.496 0.760 After post cure 200° C. for 4 hours Durometer, Shore A, points (ASTM D2240) 64 87 Tensile strength (MPa) (ASTM D412) 9.74 7.31 Elongation at break, % (ASTM D412) 342 46.8 Tear strength, kN/m (ASTM D624 Die B) 38.5 4.7 Specific gravity (ASTM D792) 1.125 1.151 Static CoF (GB/T 10006-1988) 0.525 0.097 Kinetic CoF (GB/T 10006-1988) 1.227 0.155

[0127] Again it can be seen that the kinetic coefficient of friction of the composition of Ex. 17 is much lower than the kinetic coefficient of friction of C.7, due to the combination of components (i) and (ii) as hereinbefore described with the differing vinyl content together with a hydrosilylation cure package as compared to C.7 which only contains component (i) as hereinbefore described in the composition. In this instance no ptfe was present.