Heat resistance Silicone rubber in the air heat resistance than organic rubber is much better, under 150 ℃ its physical mechanical properties are basically unchanged, can be semi-permanent use, in 200 ℃ can be continuously used for more than 10000h, 380 ℃ can be used for a period of time. Silicone rubber is thus widely used as a rubber component in high temperature occasions. Silicone rubber at high temperature in the air (with oxygen) oxidation, due to methyl oxidation and then cause glue, so that the product gradually hardened, and even cracking. In the closed system, when heated, the main polymerization reaction, so that products become soft, and loss of mechanical strength. The heat resistance of silicone rubber is related to the type of raw rubber, vinyl content (crosslinking density), heat-resisting additive, the type and dosage of filler, and the ph value and moisture content of the mixed rubber. Therefore, the selection of the catalyst for the polymerization of raw rubber, the neutralization of the residual catalyst, the white carbon black filler and the structure control agent are very important.
Heat-resistant grade silicone rubber, under high temperature (>250℃) conditions, the hardness increased slowly, tensile strength and elongation at break and so on slow down.
Cold resistance Because the molecular structure of silicone rubber is amorphous, the effect of temperature on its properties is small, and it has good cold resistance. The brittleness temperature of general organic rubber is 20 ℃ to 30 ℃, while the brittleness temperature of general silicone rubber is 60 ℃ to 70 ℃.
When 7.5 (mol)% phenyl is introduced into the raw rubber, the brittleness temperature of silicone rubber can be reduced to 115 ℃, which is flexible and can be used under -90℃.
Weathering resistance Silicone rubber main chain of all saturated keys, plus si-o-si key to oxygen, ozone and ultraviolet radiation is very stable, so no need for any additives, that is, excellent weather resistance. When corona discharges occur in the ozone, the organic rubber quickly aging, and therefore the silicone rubber is not serious impact. Long exposure to ultraviolet rays and wind and rain, the physical mechanical properties of the changes are not large, through the outdoor exposure test for decades, no cracks or degradation of hair sticky and other aging phenomenon.