What is the pressure on rubber products during vulcanization?
The general principle of curing pressure is selected: soft rubber pressure should be small, hard pressure should be big pressure; thin-walled products to small, thick wall products pressure should be large; the product structure simple pressure should be small and complex structure of the pressure should be large; the mechanical properties of products requiring high pressure should be large, should be opposite some small; sulfide at high temperature, curing pressure can be smaller, lower curing temperature, curing pressure can be bigger.The size of vulcanizing pressure should be set up in the range of system pressure of vulcanizing equipment, combined with experience or through trial production, and set according to the quality of products.Usually in engineering applications, in order to increase production efficiency, within the scope of the permit
Vulcanization effect is an index to measure the degree of vulcanization of rubber. The vulcanization effect is large, which indicates that the degree of vulcanization of the rubber is deep, and the vulcanization effect is small, which shows that the degree of vulcanization of the rubber is shallow. The effect of vulcanization is equal to the product of the strength of vulcanization and the time of vulcanization. The so-called vulcanization strength refers to the degree of vulcanization of the rubber at a certain temperature, unit time, or the vulcanization rate of the rubber at a certain temperature.The vulcanization strength is large, which indicates that the vulcanization reaction rate is fast, the vulcanization time which needs to reach the same vulcanization degree is short, and the vulcanization strength is small, which indicates the sulfidation reaction rate
It can be seen that the vulcanization time can be shortened by increasing the sulfuration temperature. The process of high temperature vulcanization is injection vulcanization and electric heating flat vulcanization. Both of them can be cured at 160 DEG C or even higher. In recent years, the industry has also adopted the trend of high temperature vulcanization. In addition, the continuous vulcanization process using eutectic liquid as heating medium has also begun to use high temperature vulcanization. In the rubber injection molding process, because the rubber material has passed the preheating and plasticizing of the screw, higher vulcanization temperature (such as 175~183 DEG C) can be adopted, but the reversion or sulfuration of rubber is less affected. For example, for three yuan ethylene propylene rubber, when set 160 degrees for molding, the positive curing time is 60min, if it is changed to 200 degrees noteThe time of vulcanization is only 4min. With the use of general-purpose rubber to make small products, the vulcanization time can be l-2mm.
Usually, the selection of curing pressure need to consider several factors, namely rubber formulation, rubber plastic size, forming die structure (filling pressure, injection pressure, injection type), type of curing equipment (flat vulcanizing machine, vulcanizing machine, injection machine, injection of sulfur with sulfide vacuum machine etc.) and product structure features.
The vulcanization pressure in the process of processing is the pressure on the unit area in the process of vulcanization. In general, in addition to rubberized products, other rubber products are required to exert some pressure during vulcanization. Vulcanization pressure mainly has the following points:1) prevent the bubbles from forming bubbles in the process of vulcanization and improve the compactness of the products.2) the filling flow of the filling material is driven by the power to fill the mold cavity.3) to improve the adhesion between rubber and cord and the bending resistance of products.4) improve the physical and mechanical properties of vulcanized rubber (i.e. products).
