Silicone

Silicone rubber is inorganic and unique among the elastomers. Made up of polysiloxane (silicon-oxygen backbone), it is very stable, more so than conventional hydrocarbon polymers (carbon-carbon backbone). It has exceptional resistance to chemicals (except strong acids), weathering and extreme temperatures, superior to neoprene. Only fluoropolymer elastomers outperform silicones in terms of chemical and weather resistance.

However, it is not particular strong and has low resistance to wear and abrasion. Even so, its impressive temperature resistance means it outperforms some other elastomers at extreme temperatures. At 150 degC there is almost no change in properties and some grades are capable of short periods at 300 degC. Similarly, at very low temperatures silicone retains its elasticity for longer than other synthetic rubbers. The intermolecular forces acting between the polymer chains is very low, resulting in high elasticity and elastic recovery.

Silicone is resistant to burning, but once ignited, it will continue to decompose. It is possible to add flame retardant additives to ensure the material self-extinguishes once the heat source is removed.

It is produced from silica (SiO2), water and methanol. The silica is refined, such as from quartz sand, into silicon and synthesised through a series of chemical reactions to produce silicone. As a thermosetting material, permanent cross-links are formed during curing, which means it cannot be easily recycled.