Vulcanization process of rubber products
A complete vulcanization system consists of vulcanizing agents, activators and accelerators
induction stage: first, interaction of sulfur, accelerator and activator is the solubility of zinc oxide in the rubber increases, activation accelerator, is a more active intermediate product produced by the reaction bbeyween accelerator and sulfur .corresponding curing curve → Scorch stage: Operating scorch time, remaining scorch time. Its length is related to the safety of production and processing, determined by the composition of rubber compound, mainly by the impact of accelerators.
operating scorch time: scorch time consumed during rubber processing due to heat accumulation effect.remaining scorch time: the time the rubber material is heated in the mold to maintain fluidity.crosslinking phase: cross-linkable free radicals (or ions) react with the molecular chains of rubber to form cross-links corresponding to the cure curve → Thermal vulcanization: the length of time depends on the temperature and the compound formulation. The higher the temperature, the more the amount of accelerator, the faster the cure rate.the slope of the curve represents the rate of sulfidation reaction. The greater the slope, the faster the sulfidation rate and the higher the production efficiency.network formation stage: At the early stage of this stage, the cross-linking reaction has been formed, the initial stage of the cross-link shortening, rearrangement and cleavage reaction, and finally the network tends to be stable, to obtain a network of relatively stable vulcanizates.corresponding to the curing curve → flat vulcanization stage: the early stage of network formation, the crosslinking reaction has been basically completed, followed by cross-linking rearrangement, cracking and other reactions, plastic strength curve flattening, flat vulcanization time depends on the compound formula.corresponding to the curing curve → over-curing stage: the late formation of the network, there are cross-linked rearrangement, because this time mainly cross-link and the thermal cracking of the bond, so the elastic properties of rubber significantly decreased.