Application of special high-performance flame-retardant silicone rubber

At present, the flame-retardant requirements of silicone rubber products in the fields of wires and cables, new energy vehicles, aerospace, electronics and electronics at home and abroad are increasing. High-performance flame-retardant silicone that meets UL94 V2/V1/V0 has become a product with great potential in the future flame-retardant material consumption market.

The flame-retardant effect of silicone rubber itself is not good, and the combustion test results are much worse than the theory. It is necessary to add flame-retardant fillers to improve the flame-retardant performance of silicone rubber.

The combustion of silicone rubber is a very complex physical and chemical process, mainly including the following reactions:

Oxidative decomposition of side chain organic groups

The side chain organic groups will be oxidized in high temperature air, decompose into small molecules, and cause intermolecular cross-linking with silica bonds.

Thermal rearrangement degradation of main chain

Uncapped or partially capped silicone rubber usually contains a certain amount of terminal hydroxyl groups. The terminal hydroxyl groups will cause the cleavage degradation reaction of the molecular main chain at high temperature, thus decomposing the small molecular cyclosiloxane. When the temperature is higher, even the completely terminated silicone rubber molecular chain will undergo thermal degradation rearrangement of the silica main chain and decompose into small molecular siloxanes; When the temperature exceeds 300 ℃, Si-C in the side chain of silicone rubber will also be cracked to produce methane and other organic gases; In addition, the combustion of silicone rubber at higher temperatures can generate silicon dioxide. The surface of silicone rubber will form a ceramic layer composed of carbon, silicon and oxygen elements. The ceramic layer has a certain strength, which can block the heat transfer and limit the exchange of combustible gas and oxygen.

At present, ROHS directive, WEEE directive and new flame retardant regulations have led more and more countries to restrict or prohibit the use of halogen-containing flame retardants. The application prospect of non-toxic, halogen-free and high-efficiency flame retardant is quite broad, and it is also imperative. Based on the requirements of environmental protection, halogen-free flame-retardant silicone rubber has attracted attention. Halogen-free flame retardants commonly used in silicone rubber include aluminum-magnesium flame retardants, carbonization or promotion, platinum flame retardants and nano flame retardants, intumescent flame retardant technology, nano composite material technology, etc.