Ethylene-propylene rubber (EPDM)
One. Manufacture of ethylene-propylene rubber
At present, there are more than 100 brands produced by nearly 20 companies in the world. At present, EPDM is still imported from Japan, the Netherlands, and the United States.
two. Classification of ethylene-propylene rubber
According to whether the third monomer is added, it is divided into: ethylene propylene diene rubber (EPM) and ethylene propylene diene rubber (EPDM)
three. Structure of Ethylene Propylene Gum
1. Saturation and non-polarity
EPM is a completely saturated rubber. The EPDM main chain is fully saturated, with only 1% to 2% (mol) of unsaturated third monomers in the side groups. EPM has extremely high chemical stability and high thermal stability. In addition, ethylene-propylene rubber is not easily polarized, does not generate hydrogen bonds, is a non-polar rubber, is resistant to polar media, and has excellent electrical insulation properties.
2. Composition ratio of ethylene to propylene
The composition ratio of ethylene and propylene affects the performance of the copolymer. Generally, a propylene content of 30 to 40% (mol) is a better elastomer.
3． Content of the third monomer
In order to make the third monomer uniformly distributed in the ethylene-propylene rubber, a batch method is generally adopted during polymerization. When the amount of the third monomer is large, the unsaturated degree is high, the vulcanization speed is fast, and the compatibility with the unsaturated rubber is good. It can be used in combination with the unsaturated rubber, but the heat resistance and aging resistance are reduced.
four. Properties of ethylene-propylene rubber
1. Small proportion
The specific gravity is 0.86, which is the smallest among all rubbers.
2. Excellent aging resistance
????① Excellent ozone resistance: Ethylene-propylene rubber is known as: "crack-free rubber". Among general-purpose rubbers, it has the best ozone resistance, followed by IIR and CR.
????② Excellent heat aging resistance: The aging resistance of ethylene-propylene rubber is the best among general rubbers. It can be used for a long time at 130 ℃, and it can be used intermittently or short-term at 150 ℃ or higher. And EPM is better than EPDM.
????③ Excellent weather resistance: The weather resistance (light, heat, wind, rain, ozone, oxygen) of ethylene-propylene rubber is the best among all general rubbers, and the service life of roofing waterproofing membrane can reach more than 25 years. .
3． Excellent electrical insulation performance
The insulation resistance of ethylene-propylene rubber is very good, comparable to IIR, and EPM is better than EPDM. It can be used as a cable material, especially the electrical properties change little after immersion in water, especially suitable for electrical insulation products and insulation products operating in water .
4． Excellent chemical resistance
Due to the chemical stability and non-polarity of ethylene-propylene rubber, it does not react with most chemicals, and is either incompatible or extremely miscible with polar substances, such as alcohols, ketones, acids (acetic acid, formic acid) , Strong base, oxidant (H2O2, HClO), detergent, phosphate esters, etc.
5. Excellent resistance to water, superheated water and steam
Water is a highly polar substance. Ethylene-propylene rubber is a kind of high molecular alkane, which is hydrophobic. It is not easy to produce physical and chemical interactions between the two, so it has excellent water resistance, super hot water resistance, and steam resistance. (EPM ＞ IIR ＞ SBR ＞ NR ＞ CR)
Fives. Cooperation and processing
1. Cooperation:
①Vulcanization system: EPDM can use sulfur vulcanization system. The amount of sulfur used is 1 ~ 2 parts. Accelerators should be used with more active varieties or different accelerators. This can ensure vulcanization speed and prevent frosting. Take domestic EPDM (D) as an example: EPDM100 stearic acid 1 zinc oxide 5 promote M0.5 TMTD1.5 S1.5 HAF50
② Reinforcing system: Since ethylene-propylene rubber is non-crystalline rubber, it is necessary to add a reinforcing agent.
③ Plasticizing system: The most commonly used plasticizers for ethylene-propylene rubber are petroleum-based plasticizers, including naphthenic oil, paraffin oil, and aromatic oil. Among them, naphthenic oil has good compatibility with ethylene-propylene rubber.
④ Tackifier: Ethylene-propylene rubber has poor self-adhesion and adhesion to other materials. When mixing, tackifiers such as alkyl phenol resin, petroleum resin, terpene resin, and rosin can be added to it.
⑤Protection system: Although the aging resistance of ethylene-propylene rubber is very good, in the case of long-term use at higher temperatures, it is still necessary to add an antioxidant, and amines are commonly used.
2. machining:
The processing of ethylene-propylene rubber has the following characteristics: ethylene-propylene rubber is not easy to roll, and it is not easy to eat carbon black. It has a better dispersion effect by compaction, and the loading capacity is 15% higher than normal. In order to improve the bonding performance, a method of increasing the bonding temperature and increasing the bonding pressure may be adopted.
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