Polymerisation phase are the following:
- the chemical reaction between silicon and methyl chloride produces dimethylchlorosilane
- dimethylchlorosilane hydrolysation produces cyclic and linear siloxane
- polymerisation produces polysiloxane
The most used polymer in industry is polydimethyl siloxane (PDMS). Silicone polymers are used in industrial applications, especially in the making of silicone rubber, obtained by adding reinforced silicon.
Silicone rubber which undergoes a polycondensation process, reticulates at room temperature by adding tin-based catalysts. Therefore, it is resistant to chemical risks. The working process at room temperature is slower, and thus reticulation could be delayed.
LSR silicone rubbers are generally vulcanised by polyaddition; in the last years, this vulcanisation technology has been strongly used even for HTV silicone rubbers. Polyaddition vulcanisation is done by using platinum catalysts, even at room temperature. The process creates a yield of nearly 100%, and needs very short working times.
Peroxide vulcanisation is used in the making of HTV silicone rubber. The catalysts used in the vulcanisation are organic peroxides which decompose at high temperature and create an ethylene bridge among the polymer molecules. At the end of the vulcanisation process, a post-vulcanisation process is sometimes applied as well.