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What are the properties of silicone rubber

Jul 29, 2017

What are the properties of silicone rubber?

Heat resistance

Heat resistance of silicone rubber in the air is much better than that of organic rubber, at 150 DEG C, the physical and mechanical properties basically unchanged, semi permanent use, under the temperature of 200 DEG C can be used continuously for more than 10000h; 380 DEG C can be used for some time. Silicone rubber is therefore widely used as rubber parts in high temperature applications. When silicone is oxidized at high temperatures in air (oxygen), it is gradually hardened and even cracked due to the oxidation of methyl. When heated in a confined system, depolymerization occurs, softening the product and even losing mechanical strength. Heat resistance of silicone rubber and rubber, both types of vinyl content (crosslinking density), heat resistant additive, filler type and amount, is also related to the mix of pH value and water content etc.. The polymerization catalyst selection of raw rubber, and residual catalyst after reaction, silica and other fillers and structure control agent selection are very attention. Heat resistant grades of silicone rubber at high temperature (>250 degrees Celsius) conditions, hardness increased slowly, tensile strength and elongation at break also decreased slowly.

Cold tolerance

The molecular structure of silicone rubber was amorphous, the temperature has little effect on its performance, and has excellent cold resistance. The brittleness temperature of the general organic rubber is from -20 DEG C to -30 DEG C, while the brittleness temperature of the general silicone rubber is between -60 and -70 degrees centigrade. When the rubber is introduced in 7.5 (mol)% phenyl, brittle temperature of silicone rubber can be reduced to -115 DEG C, remain elastic at -90 DEG C and can use.

Weather resistance

There are no saturated bonds in the main chain of silicone rubber, and the Si-O-Si bond is very stable for oxygen, ozone and ultraviolet light, so it does not need any additives. It has excellent weatherability. When the corona discharge occurs in the ozone, the organic rubber will soon aging, so it will not affect the silicone rubber seriously. Exposure to ultraviolet light and wind and rain for a long time, the physical and mechanical properties change little, and after decades of outdoor exposure test, no cracks or degradation, hair, sticky and other aging phenomenon.

Steam resistance

Silicone rubber resistant to low pressure water vapor (below 130 degrees Celsius) is quite good, it is immersed in warm water and boiling water for a long time, the volume increased less than 1%, and rarely affect its mechanical and electrical characteristics. However, water vapor over 140 DEG C can lead to the fracture of Si-O-Si backbone, which decreases the physical and mechanical properties of silicone rubber rapidly. The water vapor resistance of silicone rubber is related to the type and dosage of filler used, the density of cross linking, and the kind of vulcanizing agent

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