It is one of the important indicators of rubber products. The life of many rubber products is directly related to tensile strength. For example, the durability of the rubber cover of the conveyor belt and the rubber shock absorber are improved as the tensile strength is increased.
A: The tensile strength is related to the structure of the rubber:
    When the amount is small, the secondary valence of the intermolecular interaction is smaller. Therefore, when the external force is greater than the intermolecular effect, intermolecular sliding will occur and the material will be destroyed. Conversely, the molecular weight is large, the intermolecular force is increased, the cohesion of the rubber compound is increased, and the chain segment is not easy to slide when stretched, so the degree of damage to the material is small. All other factors affecting intermolecular forces have an impact on tensile strength. For example, there are crystalline substituents on the rubber main chains such as NR / CR / CSM, the intermolecular valence is greatly increased, and the tensile strength is also increased. That is one of the main reasons why these rubbers have good self-reinforcing properties. Generally, as the crystallinity increases, the tensile strength increases.
B: Tensile strength is also related to temperature:
    The tensile strength at high temperature is much lower than that at room temperature.
C: The tensile strength is related to the crosslinking density:
    As the crosslink density increases, the tensile strength increases. After the maximum value appears, the crosslink density continues to increase, and the tensile strength will decrease significantly. The tensile strength of vulcanized rubber decreases as the cross-linking bond energy increases. Natural rubber that can produce tensile crystals, with early breaking of weak bonds, is good for orientation crystals of the main health, so higher tensile strength will occur. Through the vulcanization system, using sulfur vulcanization, and selecting and using accelerators, DM / M / D can also improve the tensile strength (except for carbon black reinforcement, because carbon black generates heat).
D: Relationship between tensile strength and filler:
    Reinforcing agent is one of the important factors affecting tensile strength. The smaller the filler diameter, the larger the specific surface area and the greater the surface activity. The better the reinforcing performance. The vulcanizate of crystalline rubber has a monotonous decrease because it is a self-reinforcing non-crystalline rubber such as styrene butadiene, with the increase of the amount of reinforcing performance, excessive use will reduce the interest. Low dissatisfaction rubber can reach the maximum value with the increase of the amount can remain unchanged.
E: Relationship between tensile strength and softener:
    Adding softening agent will reduce the tensile strength, but adding a small amount, generally less than 7 parts on the opener, and less than 5 parts on the compactor will improve the dispersion, which is conducive to improving the tensile strength. The degree of reduction in tensile strength varies with different softeners. General natural rubber is suitable for vegetable oils. Aromatic oils for non-polar rubber such as SBR / IR / BR. Such as paraffin oil and naphthenic oil for IIR / EPDM. NBR / CR uses DBP / DOP.
    Other methods to improve tensile strength include blending rubber with resin, chemical modification of rubber, and surface modification of fillers (such as lauric)