Rubber Products Sealing Performance And Shock Absorption Performance
Rubber products (such as sealing products) is used in the compressed state, the compression performance is one of the main properties affecting the quality of the product, rubber compression resistance is generally compressed with permanent deformation to constant.
Rubber in the compressed state, will inevitably occur in physical and chemical changes, when the compression force disappears, these changes prevent the rubber back to its original state, resulting in a permanent compression deformation. The size of the compression set depends on the temperature and time of the compressed state, as well as the temperature and time at which the height is restored.
The size of the compression set is one of the important indicators to measure the sealing performance and damping performance of rubber products and the long service life.
It is very significant to study the factors that affect the compression and permanent deformation of vulcanized rubber, and it is very significant for the production and testing of rubber sealing products and shock absorbing products.
The factors influencing the compression and permanent deformation of vulcanized rubber are as follows:
First, the rubber formula factors
1, raw rubber varieties, 2, additives and dosage
The two affect the cross-linking density, thus affecting the compression of permanent deformation.
Second, the processing technology factors
1, with the dispersion of the agent, 2, cross-linked bond to the size
Vulcanizing agent and accelerator dispersed in the compound uneven, will cause the vulcanization of different parts of the product vulcanization of different degrees, resulting in vulcanized rubber cross-linked network structure there is a large flaw, so that the performance degradation, while compressed permanent Deformation also increased.
Therefore, the proper mixing method can be used to reduce the compression and permanent deformation of the vulcanizate by modifying the surface of the additive particles, reducing the agglomeration of the particles and improving the dispersion.
The vulcanization of vulcanized rubber at low temperature is mainly determined by the size of crosslinking density. The effect of crosslinking bond size on compression set at high temperature exceeds the effect of crosslink density.
Due to the vulcanization temperature is too low or the vulcanization time is not enough to cause the vulcanization of rubber, will greatly increase the compression of permanent deformation, affecting the use of rubber products performance. Acrylic rubber, silicone rubber, fluorine rubber and other special rubber will basically use two-stage vulcanization to reduce the vulcanized rubber compression deformation.
Heat shrinkability of vulcanized rubber
The heat-resistant compression properties of the vulcanized rubber are mainly determined by the type of rubber, the structure and density of the crosslinked bonds, and the test conditions. Fillers, plasticizers, antioxidants and other compounding agents.
Accordingly, we should be careful in designing recipes:
1, cross-linked structure, polysulfide easily decomposed heat resistance is poor, to try to avoid high sulfur low to promote the system. Single sulfur bond, the decomposition temperature is high, good heat resistance, so sulfur vulcanization should try to use low sulfur and high system. Carbon carbon bond decomposition temperature is higher, the best heat resistance, so can use DCP-S system is the best.
2, cross-linked bond density cross-density, permanent deformation of small. Due to the permanent deformation of the molecular chain between the occurrence of viscous flow, cross-linked to avoid the relative slip between molecules, reducing the permanent deformation.
In the design of the formula, you can increase the amount of vulcanization system to improve the cross-linking density, the amount of ZnO + stearic acid will increase the appropriate increase in cross-linking density. The use of peroxide vulcanization is also helpful in adding crosslinking aids.