We all know that when using EPDM rubber to produce rubber products, the hardness has a great influence on the quality of the finished product. For example, for EPDM rubber seals, the higher the hardness, the higher the stress generated by the rubber compound at the same compression ratio. The better the sealing effect; but this does not mean that the higher the hardness of EPDM rubber, the better; the hardness of EPDM rubber and reclaimed rubber is generally between 50-65. Rubber products manufacturers need to adjust EPDM according to specific needs. Rubber product formula, appropriate to reduce the hardness of the rubber 1JLYY819.
Theoretically, the hardness of rubber products = rubber extrusion hardness + compounding agent dosage × hardness change value, wherein the compounding agent mainly refers to rubber filler and rubber softener, so the use of EPDM rubber or EPDM reclaimed rubber to produce low hardness molding When it comes to rubber products, it is advisable to start with the types and amounts of fillers and softeners.
1. Avoid using reinforcing agents that can significantly increase the hardness of the compound.
The rubber reinforcing agent can significantly improve the physical and mechanical properties of the rubber in the production of EPDM rubber products. Carbon black and white carbon black are the most commonly used reinforcing agents. The research shows that: 1 part of super wear-resistant carbon black, super resistant Charcoal black and meteorological white carbon can increase the hardness of 5/2, so the low hardness molded EDPM rubber product formula needs to avoid using these kinds of carbon black, white carbon black, high wear-resistant furnace black, semi-reinforcing Replace carbon black or use semi-reinforcing carbon black as a reinforcing agent.
At present, there are two main ways to reduce the production cost of EPDM rubber products. One is to use reclaimed rubber and the other is to use rubber filler. In actual production, the rubber filler can also improve the hardness of the rubber to a certain extent. For example, one clay can increase the hardness of 1/4, and one part of calcium carbonate can increase the hardness of 1/6, so the low hardness EPDM rubber Preferably, the filler in the product formulation uses calcium carbonate, and the surface activated calcium carbonate has a lower hardness value.
2. Rational use of rubber softening plasticizer to adjust the hardness of EPDM compound
The softening plasticizer can reduce the hardness of the rubber compound and improve the elasticity and resilience of the rubber product in the production of rubber products. The hardness values of different types of softening plasticizers can be reduced. Paraffin oil is often used as a softening plasticizer when using ethylene propylene diene monomer or EPDM reclaimed rubber to produce low hardness rubber products. The effect of other common softening plasticizers on hardness values is as follows: usually 1 part of mineral rubber can reduce 1/5 hardness value, 1 part of ester plasticizer can reduce 1/1.5 hardness value, 1 part of naphthenic oil can reduce 1/2 hardness Value, 1 part aromatic oil reduced by 1/1.7 hardness value.
When using ethylene propylene diene monomer or EPDM reclaimed rubber to produce low hardness molded rubber products, the amount of reinforcing filler and rubber softener can be calculated by its effect on the hardness. When sulfur is used as the vulcanizing agent for the vulcanization system of low-hardness rubber products, the more sulfur is used, the higher the crosslinking density, and the higher the hardness of the rubber compound. Therefore, it is necessary to appropriately control the amount of sulfur.