(1) Silicone base polymer

The basic component of additive liquid silicone rubber is silicone basic polymer, which is mainly polydiorganosiloxane containing two or more silicon vinyl groups. It is usually a linear silicone polymer with a vinyl at both ends of the polymer chain, and some contain a small amount of silicon vinyl links in the middle of the polymer chain. The typical basic polymer most used is α,ω- Divinylpolydimethylsiloxane, or vinyl silicone oil for short.

In the production process of additive liquid rubber, the vinyl terminated silicone oil used for the base polymer of transparent liquid silicone rubber must completely eliminate the silicone hydroxyl terminated polymer, so as to avoid affecting the heat resistance of silicone rubber due to the possible release degradation of silicone hydroxyl terminated polymer at elevated temperature; The elimination of silicon hydroxyl can also ensure the normal progress of platinum catalyzed silicon vinyl and silicon hydrogen addition reaction, avoid the side reaction of condensation dehydrogenation of silicon hydrogen and silicon hydroxyl, and eliminate the influence of hydrogen composition on the light transmittance of silicone rubber.

According to the process performance and service performance requirements of the finished silicone rubber, the molar mass and distribution of the basic polymer shall meet the specific requirements. The rubber filled with reinforced silicone resin can reach the appropriate viscosity, and the vulcanized silicone rubber can reach the required mechanical strength.

(2) Crosslinking agent

The basic component crosslinking agent of addition liquid silicone rubber is organosiloxane oligomer containing three or more silicon hydrogen bonds, that is, methyl hydrogen containing silicone oil with low viscosity.

(3) Catalyst

Although there are many kinds of catalysts that can initiate hydrosilylation, the catalysts that can be used for addition molding liquid silicone rubber are only group VIII transition metal elements and their compounds or complexes, among which platinum catalysts have the highest catalytic efficiency.

Direct application of platinum catalysts can catalyze hydrosilylation vulcanization of silicone rubber at room temperature; A catalyst for medium temperature vulcanization can be prepared by adding an appropriate amount of inhibitor to platinum catalyst.

(4) Filling reinforcement material

The mechanical strength of vulcanized silicone rubber crosslinked by silicone base polymer and hydrogen containing silicone oil is not high. In order to improve the mechanical strength of vulcanized silicone rubber, reinforcing filler needs to be added to the silicone rubber system. The most commonly used reinforcing fillers are fumed silica, precipitated silica, quartz powder, etc; To obtain colorless and transparent silicone rubber, methyl vinyl MQ silicone resin needs to be used as transparent reinforcing filler.

(5) Other additives

Different additives are needed to adjust the process performance or service performance of silicone rubber. Pigment or dye shall be used as colorant to mix the color of compound; In order to improve the heat resistance of silicone rubber, heat-resistant additives need to be added; In order to improve the adhesion of silicone rubber, tackifier and other auxiliary components should be introduced.