What are the main factors affecting the tensile strength of rubber?

Rubber, as an important industrial material, is widely used in various fields. Its tensile strength is an important indicator for measuring the ability of rubber products to resist tensile failure. So, what are the main factors that affect the tensile strength of rubber? This article will provide you with a detailed popularization of this topic.

Molecular structure and molecular weight

The molecular structure of rubber has a significant influence on its tensile strength. Strong intermolecular forces, such as the presence of polar and rigid groups, will enhance the intermolecular interactions, thereby increasing tensile strength. In addition, molecular weight is also one of the key factors. Generally speaking, the tensile strength of rubber increases with the increase of molecular weight. This is because the increase in molecular weight will cause the van der Waals forces between the chain segments to increase, making the chain segments less likely to slide. This is equivalent to forming more physical crosslinking points between the molecules, thereby enhancing the tensile strength. However, when the molecular weight increases to a certain extent, the increase in tensile strength will tend to balance.

2. Crystallization and Orientation

The crystallinity of rubber and the orientation of its molecular chains also have an impact on its tensile strength. For rubbers that can crystallize (such as NR, CR, etc.), an increase in crystallinity will enhance tensile strength. Because the molecular arrangement in the crystalline region is more orderly, the intermolecular interaction is stronger. In addition, during the stretching process, the rubber molecular chains will be oriented. The molecular chains parallel to the stretching direction will bear more stress, thereby enhancing the tensile strength in that direction. However, the tensile strength in the vertical direction may decrease as a result.

3. Crosslinking density and crosslinking bond type

The crosslinking density of rubber and the type of crosslinking bonds are also important factors affecting its tensile strength. Both excessively high and low crosslinking densities are not conducive to the improvement of tensile strength. Excessively high crosslinking density can cause rubber to become hard and brittle, and brittle fracture is prone to occur during stretching. However, a crosslinking density that is too low will make the rubber overly soft and unable to effectively resist tensile stress. In terms of crosslinking bond types, polysulfide bonds have relatively high tensile strength. This is because weak bonds can play a role in stress release under stress conditions, reducing the degree of stress concentration and enabling the crosslinking network to uniformly withstand greater stress.

4. Fillers and softeners

The types and quantities of fillers and softeners will also have an impact on the tensile strength of rubber. The smaller the particle size of the filler, the larger the specific surface area and the greater the surface activity, the better the reinforcing effect will be, thereby enhancing the tensile strength. However, there is also an optimal value for the amount of filler. Too much or too little filler is not conducive to the improvement of tensile strength. Although the addition of softeners can improve the processing performance of rubber, it will also result in a certain loss of tensile strength. The compatibility of softeners with rubber can also affect the change in tensile strength.

5. Other factors

In addition to the above main factors, the tensile strength of rubber may also be affected by other factors, such as the type of rubber, vulcanization system, processing technology, etc. Different types of rubber have different chemical structures and physical properties, so their tensile strengths will also vary. The selection and optimization of the vulcanization system will also affect the crosslinking structure and tensile strength of rubber. In addition, parameters such as temperature, pressure and time in the processing technology will also have an impact on the tensile strength of rubber.

In conclusion, the main factors influencing the tensile strength of rubber include molecular structure and molecular weight, crystallization and orientation, crosslinking density and crosslinking bond type, fillers and softeners, as well as some other factors. Understanding the influence laws of these factors on the tensile strength of rubber can help us better design and prepare rubber products with excellent performance.

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