Silicone rubber
Silicone rubber is one of the important products in silicone polymer. Among all rubbers, silicone rubber has the widest working temperature range (-100 ~ 350℃) and excellent high and low temperature resistance. According to its vulcanization mechanism, silicone rubber can be divided into three categories: organic peroxide initiated radical cross-linking (hot vulcanization), polycondensation (room temperature vulcanization) and addition reaction.
(1) hot vulcanized silicone rubber (RTV) : hot vulcanized silicone rubber, also known as high temperature vulcanized silicone rubber, where the molecular weight between 500,000 and 800,000 straight chain siloxane are high temperature vulcanized silicone rubber, RTV for short. Usually with octylcyclotetrasiloxane (D4) as the main raw material under the catalytic action of acid or alkali ring-opening polymerization of raw rubber, and then by using oxide as cross-linking agent, and with a variety of additives (such as reinforcing filler, heat stabilizer, structure control agent, etc.), in the rubber mixer mixing into homogeneous mixing agent, Then, by means of molding, extrusion, calendering and other high temperature vulcanization into a variety of rubber products.
(2) room temperature vulcanized silicone rubber (LTV's) and addition reaction type silicone rubber (LSR) : Room temperature vulcanized silicone rubber refers to the low molecular weight active linear polysiloxane as the base compound, with crosslinking agent, catalyst, do not need to heat at room temperature can silicone rubber, generally referred to as LTV's. Addition reaction silicone rubber refers to the addition reaction under the catalysis of platinum compounds, and no by-products are generated during the reaction. It is usually composed of vinyl-ended polydimethylsiloxane, silicone resin, low molecular weight hydrogen-containing silicone oil, platinum catalyst, reaction inhibitor, etc., also known as liquid silicone rubber, generally referred to as LSR. Because the addition reaction type silicone rubber is usually vulcanized at room temperature (medium temperature), it is generally classified as room temperature vulcanized silicone rubber. In this paper, the above two are referred to as room temperature vulcanized silicone rubber; Room temperature vulcanized silicone rubber has a low molecular weight (generally 10 to 80 thousand), usually a viscous liquid. According to the packaging form, it can be divided into one component RTV silicone rubber and two components RTV silicone rubber. The former is the base compound, filler, crosslinking agent or catalyst in anhydrous conditions mixed evenly, sealed packaging, in the atmosphere of the wet gas reaction. The latter is the base compound and crosslinking agent or catalyst separate packaging, use according to a certain ratio of mixing will occur crosslinking, has nothing to do with environmental moisture. According to the vulcanization mechanism, it can be divided into condensation type and molding room temperature vulcanization silicone rubber two types.