Organic silicone rubber is also known as organic siloxane or silicone rubber. The main molecular chain is -Si-O- bond, with univalent organic groups as the side base of linear polymer, according to the vulcanization temperature is divided into high temperature and room temperature vulcanized silicone rubber two categories, the first is the molecular weight of 100X104 or more solid glue, the latter is the molecular weight of 1X104~5X104 viscous liquid. The Si-O bond energy (370kJ/mol) is much higher than the C-C bond energy (240kJ/mol), and the molecular chain is flexible, so the high and low temperature resistance is excellent, and the use temperature is -70~300℃; At the same time, the electrical insulation performance is excellent, and it has no toxic effect on human tissues. It is suitable for high temperature sealing parts, insulating parts, profiles, hose diaphragm and medical and health products of air system. Room temperature vulcanized silicone rubber is mainly used in the production of aircraft cabin, fuselage and integral fuel tank sealant and building waterproof, leakproof sealing materials. Compared with dimethyl silicone rubber, methyl vinyl silicone rubber has wider temperature range, better strength and lower compression permanent deformation. The low temperature performance of phenyl silicone rubber is better, it is still elastic at 100℃, and has higher heat resistance and radiation resistance. Fluorosilicone rubber has the advantages of fluororubber and silicone rubber, and can withstand mineral oil and chemical solvents.
main performance
The polymers composed of silicon-oxygen main chain and silicon-carbon side chain are collectively referred to as organosilicon polymers, and the elastomeric linear polymer is called organosilicone rubber. Because there are inorganic polymer chains in silicone polymer, it has a wide operating temperature range, excellent electrical properties, and good weather resistance, ozone resistance and moisture resistance. Good resistance to high and low temperatures. It can work at 250~300℃ for a long time, instantaneous, can withstand thousands of degrees of high temperature; At -70~100℃, it can still maintain elasticity. Silicone rubber has the widest temperature range of all rubbers. It has excellent ozone aging resistance, oxygen aging resistance, light aging resistance and weather aging performance. Excellent electrical insulation. It is tasteless, non-toxic and has no adverse effects on the human body. The surface layer is hydrophobic, non-stick to many materials, and can play an isolating role. At the same time, it has low moisture absorption and can be used in wet conditions. Good air permeability and moisture permeability. At room temperature, the permeability of nitrogen, oxygen and air is 30 to 40 times higher than that of natural rubber. Fire, shock and mildew resistant. Good mechanical properties.
performance feature
The radiation stability of silicone rubber is not very high, and its performance deteriorates sharply with the increase of irradiation temperature. Some mixtures of fillers and rubber mixtures can improve the radiation stability of undeformed silicone rubber. When there is no filler, organic silicone rubber can withstand 0.1~10kGy absorbed dose irradiation. At 20~50kGy, its dielectric properties change little, and the radiation effect is similar to thermal aging, which is a superposition sum. When asbestos filler is contained, the breaking strength increases by 10%, the shear strength decreases by 5%, the hardness and density increase by 5% after 1 MGy absorbed dose irradiation. The structuring rate of polydimethylorganosilicon based rubber increased with increasing irradiation temperature, and the structuring yields were 1.9, 2.2, 3.0, 4.2 and 3.2 at -180, -80, 25, 150 and 300℃, respectively. Temperature reduction, structural and degradation processes both reduce activity, and structural activity decreases faster.
The temperature dependence of the structuring rate of the rubber mixture with polydimethylorganosilicon as the base material does not follow Arrhenius formula when γ-irradiated. It is considered that the reaction kinetics of irradiated systems containing fillers is complex because of the adsorption of oxygen and other active groups on the surface.