Rubber raw material knowledge——EPDM

Ethylene propylene rubber is an elastomer made by copolymerization of ethylene, propylene or ethylene, propylene and a small amount of non conjugated dienes under the action of catalyst by solution method or suspension method. Ethylene propylene rubber can be divided into ethylene propylene diene monomer (EPDM) and ethylene propylene diene monomer (EPDM).

Ethylene propylene rubber has excellent aging resistance (the best of general-purpose rubber), ozone resistance and heat resistance (ethylene propylene rubber can be used for a long time at 150 ℃ and intermittently at 170 ℃). Ethylene propylene rubber has the lowest specific gravity, can be filled with high oil content without affecting the characteristics, and can be made into low-cost rubber products. At the same time, it has excellent electrical insulation and corona resistance. Good resistance.

The third monomer of EPDM is mainly ENB and DCPD. Due to the introduction of the third unsaturated monomer, EPDM can be used as a non-polar substance, which has good resistance to polar solutions and chemicals, and low water absorption. Except for strong acids, it vulcanizes ordinary acid and alkali sulfur, but has the characteristics of maintaining most of the saturated ethylene propylene rubber. The most widely used is ENB-EPDM, which is much faster than DCPD products. According to FDA, ENB-EPDM with ENB content no more than 5% can be used in food grade rubber products. With the increase of the third diene monomer, the vulcanization rate of rubber is accelerated, with lower compression deformation and higher constant elongation.

The ethylene propylene diene diene monomer (EPDM) for normal commercial use ranges from 80:20 to 50:50 for ethylene and propylene. The higher the ethylene content, the higher the tensile strength, the higher the crystallization, the lower the glass transition temperature, the worse the low temperature characteristics and compression set, and the worse the processability (calendering mixing). The higher the propylene content is, the better the processability, low temperature characteristics and compression deformation are.

Ethylene propylene rubber is commonly used in the manufacture of heat-resistant conveyor belts, steam hoses, building waterproof materials, tire sidewalls, inner tubes, vehicle shock absorbers, sealing strips, dust covers, wires, cables (especially the insulation layer of medium and high voltage cables), bridge shock pads, etc. At the same time, ethylene propylene rubber is also an excellent material resistant to chloramine and water vapor.

In ASTM D2000, AA, BA and CA specifications are used normally, and DA specifications are used for special heat resistance (vulcanization with peroxide normally).