Explosion and combustion at rubber separation

When rubber products are vulcanized, there are obvious phenomena of cracking and poor fusion at the mold closing line, which is generally called "edge burning" Once it appears, it will often produce a large number of waste products and defective products, which will seriously affect normal production. The following is about this.

Phenomenon analysis, hoping to help solve the problem.

1. Cause analysis The vulcanization of rubber is a complex chemical reaction. Due to the high temperature, a large number of volatiles will be produced during vulcanization. When the rubber is vulcanized by mold closing, due to the high pressure, the rubber will react in the closed cavity, and the volatiles produced by vulcanization cannot leak out, forming a certain pressure. With the vulcanization reaction, more and more volatiles will be produced, and the internal pressure will increase, eventually breaking through the closed cavity and leaking out along the mold closing line. At this time, vulcanization has been going on for some time, and the rubber on the surface has lost its fluidity.

Irreparable, left on the final product, resulting in "burning edge"

The above analysis is only a hypothesis. If it is correct, the phenomenon of "edge burning" is easy to occur in the tool.

Products with the following characteristics:

1. Thick-walled products, due to the difficulty of heat conduction of rubber and the difficulty of simultaneous vulcanization of internal and external rubber compounds, such products

It is easy to cause the combustion condition that the surface layer of the product is vulcanized but the inside is not vulcanized.

2. Low hardness products, because such products often add a lot of softeners when designing the formula, and will contain more low-boiling volatiles, which will escape in large quantities during vulcanization. Compared with high-hardness rubber compound, it is more prone to "edge burning". 3. The mold structure design is easy to cause the product to exhaust centrally. For example, cylindrical and cylindrical products, two semicircles are combined for parting, and all volatiles produced by vulcanization are concentrated and discharged from the middle parting line.