Elasticity and low temperature properties of ethylene propylene rubber

The main chain of ethylene propylene rubber is completely composed of saturated hydrocarbons with stable chemical structure, and the monomer units of ethylene and propylene are irregularly arranged along the main chain direction. Even if a small number of unsaturated double bonds are introduced into the side chain of the molecule, but due to the absence of polar substituents in the molecule, the intermolecular cohesion energy is low, and the flexibility of the molecular chain can still be maintained over a wide range of temperatures. The high flexibility of the molecular chain determines the good elasticity and low temperature performance of ethylene propylene rubber. In the chemical structure parameters, ethylene / propylene composition ratio of ethylene propylene rubber molecular chain flexibility has a very big impact, thus directly affecting the elasticity and low temperature performance of ethylene propylene rubber. It is generally believed that the polymer has the elasticity of ordinary rubber when the ethylene content is within the range of 25% to 75% (mole fraction). And when the ethylene content exceeds this range, the polymer has poor elasticity, similar to the properties of plastic. Among general-purpose rubbers, ethylene propylene rubber is second only to natural rubber and male-butadiene rubber in elasticity, and superior to styrene butadiene rubber. For ethylene propylene rubber, only a small number of unsaturated groups introduced into the side chain, the presence of these unsaturated groups, will reduce the flexibility of the main chain of the molecule; but on the other hand, it can further increase the amorphous structure of the molecular chain to reduce the crystallisation tendency, and thus the overall view of the flexibility and elasticity of EPDM has little impact. Therefore, EPDM rubber in the elasticity and low-temperature performance, and binary ethylene propylene rubber is not significantly different.