Silicone elastomer compositions and elastomeric materials
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.
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 content;
(ii) 3 to 15% by weight of a polydiorganosiloxane polymer having ≥0.5% by weight of alkenyl 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 Si-H groups per molecule; and
(b) a hydrosilylation catalyst; or
(vi) a combination of (iv) and (v); and
further comprising:
(vii) polytetrafluoroethylene;
wherein components (i) and (ii) comprise fluorosilicone gums, the self-lubricating silicone elastomer composition is hydrosilylation curable, and the polydiorganosiloxane polymer (v) (a) is fluoro containing.
2. The self-lubricating silicone elastomer composition in accordance with claim 1 , wherein each of components (i) and (ii) have 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 2 , wherein each of components (i) and (ii) have a Williams plasticity of from 100 mm/100 to 400 mm/100 in accordance with ASTM D-926-08.
4. The self-lubricating silicone elastomer composition in accordance with claim 1 , wherein the polytetrafluoroethylene (vii) is present in an amount of from 0.75 to 5% by weight.
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 , wherein when component (v) is present there is additionally 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 , wherein the polytetrafluoroethylene (vii) has a particle size of from 250 to 750 μm.
9. The self-lubricating silicone elastomer composition in accordance with claim 8 , comprising polytetrafluoroethylene (vii) having a particle size of from 350 to 550 μm.
10. The self-lubricating silicone elastomer composition in accordance with claim 9 , wherein the polytetrafluoroethylene (vii) is present in an amount of from 0.75 to 5% by weight.
11. The self-lubricating silicone elastomer composition in accordance with claim 9 , comprising polytetrafluoroethylene (vii) having an average particle size of between 400 and 500 μm.
12. The self-lubricating silicone elastomer composition in accordance with claim 1 , which is non-oil bleeding and/or non-oil filled.
13. 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.
14. The self-lubricating silicone elastomer composition in accordance with claim 1 , wherein component (v) (a) is a polydiorganosiloxane polymer having at least 3 Si-H groups per molecule.
15. The self-lubricating silicone elastomer composition in accordance with claim 1 , wherein components (i) and (ii) each include vinyl groups.
16. A self-lubricating silicone elastomeric material which is the cured product of the composition in accordance with claim 1 .
17. The self-lubricating silicone elastomeric material in accordance with claim 16 , 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.
18. The self-lubricating silicone elastomeric material in accordance with claim 16 , 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.
19. 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 16 .
20. 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.