High strength silicone elastomers and compositions therefor
View Patent ↗Compositions for forming a silicone elastomer and the silicone elastomers thereby which have improved characteristics and which can be used for medical devices are disclosed. The composition for forming a silicone elastomer can include (A) an organopolysiloxane having silicon-bonded alkenyl groups; (B) an organohydrogensiloxane having an average of two or more silicon-bonded hydrogen atoms in the molecule; (C) an inorganic filler; and (D) a filler treatment agent which includes an alkenyl-containing group, e.g., an alkenyl-containing organosilane or organosilazane.
1. A silicone elastomer made by the process comprising:
(1) forming a composition, the composition comprising:
(A) 100 parts of an organopolysiloxane having alkenyl radicals,
(B) 0.1 to 5 parts of an organohydrogensiloxane having an average of two or more silicon-bonded hydrogen atoms in the molecule,
(C) 10 to 50 parts of an inorganic filler, and
(D) 2 to 8 parts of a filler treatment agent which includes an alkenyl-containing group; and
(2) curing the composition to form a silicone elastomer having:
(i) a Shore-A hardness of from about 20 to about 45 as measured in accordance with ASTM D2240 using a type A durometer hardness tester;
(ii) a breaking elongation of at least about 800% as measured in accordance with ASTM D412; and
(iii) a tensile strength of at least 15.0 MPa.
2. The silicone elastomer of claim 1 , further comprising in the composition (E) a catalytically effective amount of an addition reaction catalyst.
3. The silicone elastomer of claim 1 , further comprising in the composition a cure retarder.
4. The silicone elastomer of claim 1 , wherein the inorganic filler includes fumed silica having a BET specific surface area in a range of about 100 square meters per gram or greater which accounts for 30 weight % or more of the total quantity of component (C).
5. The silicone elastomer of claim 1 , wherein the filler treating agent includes a mixture of (D1) an alkenyl-free organosilane or organosilazane and (D2) an alkenyl-containing organosilane or organosilazane.
6. The silicone elastomer of claim 5 , wherein D1 and D2 have a parts by weight ratio (D1:D2) of from about 15:1 to about 5:1.
7. The silicone elastomer of claim 6 , wherein D1 is an alkyl substituted silazane and D2 is a vinyl substituted silazane.
8. The silicone elastomer of claim 1 , further comprising combining the composition with a solvent to form a dispersion or solution of the composition prior to curing the composition.
9. The silicone elastomer of claim 1 , further comprising dip or spray coating the composition on to a substrate and curing the composition to form a cured silicone elastomer.
10. A medical device including the silicone elastomer of claim 1 .
11. A medical device comprising an outer shell including the silicone elastomer of claim 1 .
12. The medical device of claim 11 , further including a filler material selected from a silicone gel or a water containing medium.
13. The medical device of claim 12 which is a breast implant.
14. The silicone elastomer of claim 1 , wherein the inorganic filler is present in the composition in 25 to 50 parts.
15. The silicone elastomer of claim 1 , wherein curing occurs at a temperature of 80-230° C. for 3 seconds to 60 minutes.
16. The silicone elastomer of claim 15 , wherein curing occurs at a temperature of 150° C. for 10 minutes.