How to improve the tensile strength and elongation of rubber products
Improve the tensile strength and elongation of rubber products. The high tensile strength formula uses natural rubber products, neoprene rubber products, chlorofluoroethylene rubber products and other crystalline rubbers, and the rubber content can reach about 60%. In addition, use excellent reinforcing fillers such as carbon black and white carbon black and disperse them evenly. When using white carbon black, the dosage should not exceed 25 parts.
When using non-crystalline rubber, increase the amount of reinforcing agent, pay attention to uniform dispersion and use a vulcanization system with a faster vulcanization speed. Reduce the amount of sulfur and use softeners or plasticizers to obtain rubber products with greater elongation. The accelerator should be thiazole, the amount should be increased appropriately to maintain the flatness of the sulfur vulcanization curve, and the filler should be added less. It is better to use clay, and carbon black can also be used, especially soft carbon black.
There are many factors that affect the strength of rubber products. In addition to the crosslink density, the main factors are as follows:
1) Deformation speed and time dependence of strength are the common laws of all materials. Under rapid force application, the strength of rubber products is higher than that of slow speed. At this time, because the molecular chain has not yet time to stretch when rapid force is applied, the chain is not yet under tension. Therefore, the chance of breaking is reduced, and the strength is increased.
2) The formula strength of elongation crystalline and non-crystalline rubber products is relatively low. For natural rubber products with elongation and crystallization, select an appropriate vulcanization system, and the strength can reach about 250 kg/cm. This is because natural rubber products crystallize in the tensile direction as the elongation increases. The crystallization of natural rubber products takes about 2 seconds or more and less than a little time, and does not show reinforcement under high-speed test conditions.
3) Temperature, the tensile strength measured at different temperatures is different. Synthetic rubber, especially rubber products with greater polarity, have higher tensile strength at low temperatures and lower tensile strength at high temperatures. Although the use of reinforcing agents can increase the strength, it is still not as good as natural rubber vulcanized rubber products. In order to improve this shortcoming. It can be used to introduce functional groups that can produce chemical cross-linking into synthetic rubber products to form main valence bonds, or to make the structure have a chemical structure with active hydrogen atoms, and use reactive halogens to increase cross-linking to improve rubber The strength of the product.
4) Molecular weight and strength increase with the increase of molecular weight. This is because when the molecular chain is long, the force between the molecules is large, and the flexibility of the molecular chain is relatively increased. For example, when there are polar substituents on the molecular chain, the If the second price increases, its strength will also increase.
5) Branching and gelation. During the polymerization process or under the action of high temperature and strong mechanical action, it can make the rubber rubber product molecules produce branched chains. The presence of the branched chains makes the macromolecules arranged irregularly. After vulcanization, the rubber products become networked. Incomplete structure may cause cracks and reduce strength. The gel produced in the polymerization process also destroys the regularity of rubber molecules, which reduces the strength of rubber products manufacturers.