In the case of vulcanization, the rubber product sometimes exhibits a poorly fused fusion phenomenon at the edge portion. Improper handling will result in a large number of waste products, which will seriously affect the normal production. As a professional rubber manufacturer, let me explain how to solve it.
From the three molding methods commonly used for molding, injection molding and injection, for the same rubber compound, the chance of burning edge is successively decreased. In particular, the injection method can accurately preheat the rubber to a higher temperature before being injected into the cavity, which effectively shortens the process of the heat transfer of the rubber after the rubber enters the cavity, especially for low-thickness thick-walled products. It has unparalleled superiority in preventing and solving the problem of burning edge.
2. Formulation design
The formula is the basis of the production of rubber products. The good formula not only can meet the performance requirements of the products, but also has good process performance and low cost, and can produce products smoothly and efficiently. For thick-walled, low-hardness products, the possibility of “burning edges” should be specifically considered in the formulation design. Try to use low-boiling volatiles with low boiling point and pay attention to the amount of control; the choice of sulfur-promoting system should pay attention to the selection of after-effect varieties to obtain longer scorch time and vulcanization flat period; if possible, Adding an additive that can improve the thermal conductivity of the rubber compound, so that the inner and outer rubbers can be simultaneously vulcanized as much as possible to avoid the formation of “burning edge” conditions.
3. Mold design
Avoiding burnt edges from mold design is also an effective method. For the mold structure of the product with the above characteristics, it is necessary to adopt a parting mode capable of dispersing the exhaust gas to avoid concentrated exhaust. If the appearance allows, it is also considered to specifically increase the vent hole and the exhaust groove, which helps to avoid ” The problem of burning edge can also avoid the phenomenon of lack of glue formation.
4. Vulcanization process
Measures can also be taken to make adjustments. The low-temperature long-time vulcanization process is the most commonly used one. Since the vulcanization temperature is lowered, the difference in the vulcanization speed of the inner and outer layers of the rubber is shortened. At the same time, the volatilization due to vulcanization is reduced due to the decrease in temperature, and thus the burning edge phenomenon is also reduced. Reducing the clamping pressure, to some extent, disperses the concentrated leakage of vulcanized volatiles, and also reduces the effect of “burning edges”.
All of the above methods help to solve the problem of edge cracking of rubber products. Solving from the formulation design is often limited by product performance and material cost, it is not easy to be effective, and the cost of solving the problem is also high. Solving from the vulcanization process also often leads to problems of reduced production efficiency. In contrast, choosing an appropriate production process, especially the injection molding of this advanced molding process, fully consider the mold division method, you can get twice the result with half the effort.