Material

Silicone Elastomers

Vulcanized ‘problem-solving’ silicone-based polymers available in sponge, foam, and solid configurations

Silicone elastomers or silicone elastomerics most often refers to silicone-based polymers that have been vulcanized. Albeit technically incorrect, the term “silicone rubber” is often used since it is more intuitive and descriptive. Silicone elastomers or silicone rubber materials are readily available in a variety of forms, such as solids, open cell foams, closed cell sponges, thermally conductive, and electrically conductive. Solid silicone sheet or solid molded silicone parts are readily available from 10 durometer Shore A (soft) to 70 durometer Shore A (firm).

Cellular Silicone Materials

Cast silicone foam and silicone sponges are made by expanding and entrapping air (closed cell) or making open pockets (open cell) during the curing process, making it very soft and compliant. Silicone foam materials are produced from a two part liquid silicone base, which are mixed and cast onto a curing belt or into a bun. Low density silicone foams are considered open cell. Silicone sponge materials are produced from milled silicone gum stock, which are catalysed, sheeted and cured in a molding press or continuous rotocure under high temperature and pressure. Silicone sponge products are considered closed cell. Closed cell silicone sheet materials normally have a textured surface, which is imparted by the Teflon™ / fiberglass bleeder cloth necessary to the curing process.

Peroxide Cure Silicones and Addition Cure Silicones

Conventional peroxide cure silicones – dimethyl polysiloxane and methyl vinyl polysiloxane – comprise the majority of the gum base molded and rotocured silicone rubber sheet on the commercial market. However, cast liquid silicones in thin gauge sheets are growing in demand. These new addition cure liquid silicones are intended especially for analytical instrumentation and healthcare applications which require the utmost purity and cleanliness of materials. The name “addition cure” derives from the vulcanization reaction which consists of a multi-functional silicon hydride cross-linker, which in the presence of a precious metal catalyst such as platinum, cures with a longer cross-link chain for added tensile strength and flexing capability over peroxide cured silicones.

Specialty Silicone Materials

Additives like boron nitride, alumina, ceramics and even coated copper particles can be mixed into the raw gum silicone compound to make it thermally conductive. Similarly, adding nickel-graphite, silver plated aluminum, silver plated copper or conductive carbon will make silicone electrically conductive. These various forms lend themselves to a sundry of applications including gaskets and pads for analytical instruments, handheld data devices, airflow management equipment, medical diagnostics devices, high tech gadgets, and other applications in the aerospace, defense, telecom and automotive industries.

These specialty elastomers can be die cut, water jet cut, custom molded, laminated and fabricated into many different components, including gaskets, cushioning pads, vibration dampening pads and many other uses. Silicone elastomer materials with special properties include electrically conductive and thermally conductive elastomers that allow components to provide EMI shielding and ESD protection.

When the business was started in 1919 as the Stockwell Rubber Company and for many decades thereafter, natural rubber, neoprene and similar organic elastomers were the materials of choice and the best available gasketing materials. Now, silicone elastomer materials are used in place of rubber in almost all work done by Stockwell Elastomerics, which was renamed in 2005 to reflect the emphasis on silicone elastomer materials.