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Vulcanization is the chemical process of converting rubber into extremely durable materials by the use of heat. It also involves heating the rubber with sulfur or other curatives to modify the polymer to form cross-links.
The advantages of using vulcanized rubber as opposed to non-vulcanized are that it’s stronger and can withstand more damage and stress. The material is more durable because its bonds are made of cross-links. Vulcanized rubber is more rigid and stress resistant, too.
Two types of silicone rubber exist — liquid and solid. Each has the same basic structure, but the curing process is what sets them apart. LSR is a two-component system, with Component A containing platinum catalyst and Component B having methylhydrogen siloxane. The latter of the two acts as an alcohol inhibitor and cross-link during the process. Although the two materials are stored separately, we mix them during the LSR process with cold runner injection molding equipment.
Vulcanization is where elastomer long chains chemically cross-link, which releases energy and makes an exothermic reaction. From there, a 3D matrix forms because a catalyst bonds the long chains together. The intricate network improves the rubber’s mechanical properties.
The vulcanization process for manufacturing automotive rubber products can create resilience and thermal stability to any product you require. When we mix the catalyst and methylhydrogen siloxane, curing begins right away. When the chemical bonds form, heat is released, which increases the temperature of the system. As the temperature of the resin increases, the viscosity decreases. It releases air bubbles and allows for better flow.
Although the temperature during the vulcanization process rises, the viscosity of the material increases. Once it reaches the appropriate gel point, the resin stops flowing, meaning the temperature and viscosity limit has been reached. As curing continues, cross-linking halts since the viscosity increases, and the diffusion rate decreases.
When it comes to automotive seals, the industry relies on our detailed vulcanization of silicone rubber process to receive top-quality products. To gain a more in-depth view of the LSR vulcanization process, see how it’s done at SIMTEC Silicone Parts.