Fire resistant thermoplastic silicone vulcanizates

Thermoplastic elastomers (TPEs) are polymeric materials, which possess both plastic and rubbery properties. They have elastomeric mechanical properties but, unlike conventional rubbers, they can be re-processed at elevated temperatures. This re-processability is a major advantage of TPEs over chemically crosslinked rubbers since it allows faster cycle times, recycling of fabricated parts, and results in a considerable reduction of scrap. A composition comprising a polyolefin, a polyorganosiloxane having at least two alkenyl groups per molecule, and calcium silicate where the polyorganosiloxane is cured after mixing using an organohydrido silicon compound and a hydrosilation catalyst to create a thermoplastic vulcanizate, provides excellent fire resistance. In particular such compositions when tested by burning at 40 to 88 kW/mexternal flux generate significantly less heat and smoke, and generate tougher chars compared to polyolefins alone, or mixtures of thermoplastic polyolefin resin, polyorganosiloxane and calcium silicate where the composition is not cured after mixing.