1. The tensile strength of rubber with small molecular weight increases with the increase of molecular weight. Generally, the tensile strength of rubber with molecular weight between 30-350,000 is the best.
2. The tensile strength with narrow molecular weight distribution is higher.
3, when there are polar substituents on the main chain, the tensile strength increases with the increase of intermolecular forces. For example, in nitrile rubber, the acrylonitrile content increases and the tensile strength increases.
4, tensile strength increases with the increase of rubber crystallinity. Such as NR, CR, CSM, IIR have higher tensile strength.
5. After the rubber molecular chain orientation, the tensile strength in the parallel direction increases, and the tensile strength in the vertical direction decreases.
6. Tensile strength decreases with the increase of crosslinking bond energy, and peaks with the increase of crosslinking density. The relationship between crosslinked bond type and tensile strength decreases in the following order: ionic bond -- polysulfide bond -- disulfide bond -- mono sulfur bond -- carbon-carbon bond
7, small carbon black particles and low structure (such as high wear resistance of low structure), surface oxygen-containing groups (such as slot black) its tensile strength, tear strength, high elongation.
8, the filler particles are small, the surface area is large, the surface activity is large, the reinforcement effect is good. As for the relationship between structure and tensile strength, the structure of crystalline rubber is not good for tensile strength, but for non-crystalline rubber is the opposite. The amount of carbon black in soft rubber is generally between 40-60 parts.
9. When the amount of softener exceeds 5 parts, the tensile strength of the vulcanized rubber will be reduced.
10. Other methods to improve tensile strength. Such as NR/PE, HS blend, NBR/PVC blend, EPDM/PP blend and so on.
