What happens during vulcanization of rubber/plastic?

Vulcanization is a process in which a rubber mixture chemically reacts under heat and pressure. During this process, carbon dioxide is released.Polymer chains crosslinked with a vulcanization agent (often sulfur), so that it becomes plastically deformable Raw rubber solid, rubber-elastic components are formed. The vulcanization process is not reversible and takes place in heated tools at temperatures between 160 and 200 °C on molded parts.

Why is crude rubber unusable without vulcanization?

Raw rubber is plastic-like without vulcanization, like a kneading mass. At the chemical level, raw rubber consists of carbon chains that slide past each other under stress, allowing the rubber material to remain permanently deformable. Furthermore, it is tacky; it softens when heated and hardens when cooled and dissolves in many solvents. It is only through the crosslinking of the chains that a form-stable, tear-resistant and durable rubber material is created, which can be used for industrial applications.

How long does the vulcanization of molded parts take?

The vulcanization of a mold part typically takes between 2 and 20 minutes depending on the mixture, temperature, and wall thickness of the mold part; however, for particularly thick components, the heating time is significantly longer. The thicker the wall thickness, the longer the heating time, as the heat must penetrate the rubber. Silicone and FKM parts are then often tempered in the oven for several hours to complete the vulcanization cost-effectively outside the mold.

What types of vulcanization are there?

The most important types of vulcanization are the Sulphur vulcanisation and the Peroxide crosslinking, which are included in the used Crosslinking chemicals The sulfur vulcanization process is most commonly used for NR, SBR, NBR and EPDM and produces cost-effective elastomer molded parts that are capable of withstanding dynamic loads. The peroxide vulcanization process is used for silicone, HNBR and EPDM and results in less pressure set residual, leaves behind smaller migration-capable particles after vulcanization and is better suited for FDA-compliant applications.