Viscoelastic silicon rubber compositions

摘要

This invention relates to viscoelastic silicone rubber compositions that are the products of the reaction of: (a) a silanol-terminated polyorganosiloxane base; (b) a boron-containing crosslinking agent; and (c) a siloxane bond-forming crosslinking agent. In a viscoelastic silicone rubber composition of the invention some of the crosslinks, the siloxane crosslinks, are permanent and others of the crosslinks, the boron-containing crosslinks, are temporary. Because a fraction of its crosslinks can come apart and then reform, a viscoelastic silicone rubber composition of the invention can relax stress in response to strain and thus adapt to new shapes. The composition has sufficient permanent crosslinks, however, to establish a permanent equilibrium shape to which the composition will eventually return when not subject to any imposed stress. A viscoelastic silicone rubber composition has sufficient temporary crosslinks to give the composition a stiffness that is greater on short timescales than it is on longer timescales.

主权项

1. A method of making a viscoelastic silicone rubber composition comprising the steps of:
reacting a silanol-terminated polyorganosiloxane base with a boron-containing crosslinking agent under conditions to produce a borosilicone compound, adding a siloxane bond-forming crosslinking agent, a catalyst, an optional filler, and an optional foaming agent to the borosilicone compound to form a mixture; and curing the mixture under conditions sufficient to form a viscoelastic silicone rubber composition, wherein the boron-containing crosslinking agent is added in an amount up to 100% saturation.