EPDM has excellent heat resistance, ozone resistance and weather resistance. It does not have reinforcement. It is often reinforced with carbon black or combined with self reinforced natural rubber. However, the molecular structure of EPDM and natural rubber is very different, the compatibility is poor, and the application conditions are harsh. Compared with natural rubber, the compatibility latex reclaimed rubber and EPDM rubber is better. Selecting the appropriate variety of carbon black can further optimize the physical and mechanical properties of the compound.
When using carbon black to improve the mechanical strength of EPDM / Latex reclaimed rubber, the variety and amount of carbon black will not only affect the physical properties of the compound, but also affect the rubber processing process, such as vulcanization process. Therefore, it is necessary to comprehensively consider various factors, select appropriate carbon black and reasonably control the amount of carbon black.
1. The particle size of carbon black affects the physical and mechanical properties of EPDM / Latex reclaimed rubber
There are a large number of active points on the surface of carbon black particles, which can produce chemical bonds that can slide along the surface of carbon black particles. When the rubber is deformed by external force, the sliding of molecular chain can absorb the impact of external force, play a buffer role, make the stress distribution uniform, and then improve the tensile strength and tear strength of the rubber.
When the EPDM / Latex reclaimed rubber compound is reinforced with carbon black, the smaller the particle size of carbon black, the higher the degree of structure, the larger the specific surface area and the higher the activity, the more the number of surface active points of carbon black. During mixing and vulcanization, more rubber macromolecular chains can be adsorbed to form more bonds, and the greater the tensile strength and elongation at break of the compound. However, if the particle size of carbon black is too small, the cohesion particles will increase, and the particles are easy to agglomerate, which is difficult to disperse during mixing, resulting in the decline of mechanical properties of EPDM / Latex reclaimed rubber.
2. The type of carbon black affects the production process of EPDM / Latex reclaimed rubber
In actual production, the smaller the particle size of carbon black, the higher the degree of structure, the more the amount of contained rubber, the increase of effective filling volume fraction, and the increase of the viscosity of EPDM / Latex reclaimed rubber mixture. In terms of vulcanization performance, the smaller the particle size of carbon black, the greater the network density of bonded rubber, which hinders the movement of rubber macromolecular chain and shortens the scorching time of EPDM / Latex reclaimed rubber.
3. Common carbon black varieties and precautions of EPDM / Latex reclaimed rubber compound
At present, carbon black varieties commonly used in rubber products industry include carbon black N220, carbon black N330, carbon black n774, carbon black n660, etc. among them, high wear-resistant furnace black N330 has better application effect in EPDM / Latex reclaimed rubber compound. In actual production, carbon black N330 contains more rubber, the more the amount is, the more the amount of adhesive is, the more the reinforcing effect is remarkable, and the physical and mechanical properties of vulcanizate are better.
It should be noted that the specific surface area of carbon black with small particle size is large, and the area that needs to be wetted is larger. Therefore, during mixing, the feeding is slow, the energy consumption is high, the heat generation is much, and the dispersion is difficult. When EPDM / Latex reclaimed rubber is filled with N330, its dosage should be reasonably controlled.
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