When rubber products are vulcanized, the phenomenon of obvious cracking and poor fusion occurs at the position of the parting line. It is generally called "burning edge". Once it occurs, it often produces a lot of waste and defective products, which seriously affects the normal production. Rubber Rings Manufacturer analyzes this phenomenon:
The vulcanization of rubber is a complex chemical reaction. Due to the effect of high temperature, a large amount of volatile matter will be generated during the process. When the rubber is vulcanized by mold clamping, due to the high pressure, the rubber will react in a closed cavity, and the volatile matter generated by vulcanization cannot leak out and form a certain pressure. With the progress of the vulcanization reaction, more and more volatile matter and internal pressure increase, finally breaking through the closed cavity and leaking along the parting line. At this time, the vulcanization has been going on for a period of time, and the rubber on the surface has been vulcanized. The liquidity is lost, and the defects formed by the impact of a large amount of volatile matter leakage cannot be compensated, and they remain on the final product, causing "burning edges".
Then the phenomenon of "burning edge" easily occurs on products with the following characteristics:
1. Thick-walled products, because the rubber heat conduction is relatively difficult, the inner and outer layers of rubber are not easy to be vulcanized simultaneously. Therefore, this kind of product is easy to cause the edge burning condition where the surface layer of the product has been vulcanized but the inside has not been vulcanized.
2. Low-hardness products, because such products often add a large amount of softener during formulation design, which will contain more low-boiling volatiles, which will escape in large quantities during vulcanization. Compared with high-hardness compounds, it is more prone to "burning edges".
3. The mold structure design is likely to cause products with the concentrated exhaust. For example, for cylindrical and cylindrical products, the splitting method of two semicircular combinations is adopted. All the volatile matter generated by vulcanization is concentratedly discharged from the middle parting line position, which often causes "burning edges" due to excessive exhaust gas concentration.