Second stage vulcanization is also called post vulcanization.It is commonly used to vulcanize silicone rubber, fluorosilicone rubber, and fluorosilicone rubber (e.g., BIPB vulcanizing agent).Secondary vulcanization can be used to supplement vulcanization, as required, but not necessarily for some species.However, it is generally necessary to carry out secondary vulcanization, such as silicone rubber.Low molecular substances such as HF released during the vulcanization of fluororubber will hinder the cross-linking of rubber and will be released at high temperature.It corrodes metal parts, so it also requires disulfide.Other fluorinated rubbers may also be cycined to produce fluorinated rings, which further improve their heat resistance.
Effect of two-stage vulcanization:
When silicone rubber is vulcanized by peroxides, low molecular compounds (such as benzene and benzoic acid, etc.) are generated after the peroxides are differentiated, which will affect the mechanical properties of rubber.Moreover, after the first stage of rubber heating forming, its crosslinking density is not good, in order to make its further response, it is necessary to increase the time or temperature, which takes up the time of the mold and vulcanizing machine, affecting the efficiency.In disulfide, peroxides are now in fact rare, and the main reason for this is to increase crosslinking by oxygen effect.Therefore, the oven should be equipped with blast equipment, and glue should not be stacked too close.
Other advantages of two-stage vulcanization, one is to remove the unpleasant smell in the rubber, the second is to do a test piece of secondary vulcanization (oven constant temperature for a period of time) can measure the aging, after the second vulcanization can increase the rubber products tear strength and tear strength, but its tear elongation decline!