Tensile stress and hardness are important indicators of the stiffness of rubber materials, which are the forces required to produce certain deformations in vulcanized rubber and are related to larger tensile deformations.
The larger the molecular weight of the rubber, the greater the effective cross-linked tensile stress. In order to obtain the specified tensile stress, the cross-link density can be increased appropriately for rubber with a small molecular weight. Any structural factor that increases the intermolecular forces. All of them can improve the deformation resistance of vulcanized rubber.
Such as CR/NBR/PU/NR etc. have higher tensile stress.
Tensile stress and crosslink density have great influence. Whether it is pure rubber or reinforced vulcanizates, as the crosslinking density increases, the tensile stress and hardness also increase linearly. This is usually achieved through the adjustment of vulcanizing agents, accelerators, co-sulfurizing agents, active agents, etc. Sulfur-containing accelerators have a significant effect on the increase of tensile stress. Multi-sulfur Ken is conducive to improve the fixed tensile stress. Filler can improve the tensile stress and hardness of the product. The higher the reinforcement property and the higher the hardness, the higher the tensile stress. Tensile stress increases with the increase of hardness, the higher the increase of filling. On the contrary, the increase of softening agent, hardness decreases and the tensile stress decreases. In addition to the increase of reinforcing agent there is also the use of alkyl phenolic resin hardness up to 95 degrees, high styrene resin. The hardness of the system can reach 85 degrees with resin RS and accelerator H, etc.
Definition of constant tensile stress is the amount of load per unit cross-sectional area that needs to be applied to stretch a specimen to a given length. It is an indicator of rubber materials, etc. Common fixed extension stress are 100%, 200%, 300%, 500% fixed extension stress. If a specimen with a cross-sectional area of 1 square centimeter is stretched by a factor of 490N (50 kg force), then the 100% constant tensile stress is 490Pa (50 kg force/c㎡).
The factors affecting the fixed extension stress are
1、The larger the molecular weight, the higher the fixed extension stress.
2、The narrower the molecular weight distribution, the lower the fixed extension stress and hardness.
3、The intermolecular force is large, the fixed tensile stress is high.
4、Standing stress and hardness increase with the increase of cross-link density. Traditional vulcanization system can obtain high tensile stress and hardness.
5、The tensile stress and hardness increase with the decrease of filler particle size, increase with the increase of structure and surface activity, and increase with the increase of filler amount.
6, fixed tensile stress and hardness with the increase in the amount of softener and reduce.
7, rubber-plastic blending can improve the tensile stress and hardness, such as NR/PE, HS blending, NBR/PVC blending, EPDM/PP blending.