The transformation of raw silicone polymers into resilient and durable silicone rubber products is a fascinating chemical process, with vulcanization or curing being the pivotal step. Among the various methods, peroxide curing stands out for its effectiveness in creating strong, stable crosslinks within the silicone polymer matrix. NINGBO INNO PHARMCHEM CO.,LTD. specializes in providing the chemical building blocks for these advanced material processes, and this article aims to shed light on the science behind peroxide curing in silicone rubber.

Silicone rubber, fundamentally a polymer chain of repeating silicon-oxygen atoms (siloxanes) with organic side groups, requires a method to create a three-dimensional network to achieve its elastomeric properties. Peroxide curing achieves this by initiating a free-radical mechanism. Organic peroxides, such as bifunctional peroxides like 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane, are designed to decompose when heated, releasing highly reactive free radicals. These radicals then abstract hydrogen atoms from the polymer backbone, creating reactive sites on the silicone chains. Simultaneously, the peroxide fragments themselves can also form radicals that contribute to the crosslinking process, often forming stable carbon-carbon bonds between adjacent polymer chains. This process is distinct from condensation or addition curing, each having its own catalytic mechanisms and end products.

A critical aspect of peroxide curing is its thermal stability and the temperature at which it becomes active. The Self-Accelerating Decomposition Temperature (SADT) is a key safety parameter for organic peroxides, indicating the lowest temperature at which self-accelerating decomposition can occur in the substance's original packaging. For many effective silicone crosslinking agents, the SADT is around 80°C, necessitating careful storage at temperatures typically below 30°C to maintain product quality and safety. The processing temperatures, however, are carefully chosen to be well above the SADT but below the point of unwanted, rapid decomposition. A typical crosslinking temperature for such peroxides might be around 175°C, where the reaction proceeds efficiently within a reasonable timeframe, such as a rheometer t90 (time to 90% cure) of about 12 minutes.

The resulting crosslinked silicone rubber exhibits significantly enhanced thermal stability. Unlike some other elastomers, silicone rubber cured via peroxides maintains its mechanical integrity and flexibility at elevated temperatures and can also perform well at very low temperatures. This broad service temperature range is a hallmark of silicone rubber and is directly facilitated by the robust and stable crosslinks formed by peroxide initiation. This makes silicone rubber an ideal choice for applications where consistent performance under thermal stress is required, such as in engine seals, aerospace components, and high-temperature electrical insulation.

NINGBO INNO PHARMCHEM CO.,LTD. is at the forefront of supplying essential chemicals that drive innovation in material science. Our understanding of the intricate chemistry behind silicone rubber vulcanization, including the precise application of organic peroxides, allows us to offer products that meet the highest industry standards. By leveraging the science of peroxide curing, manufacturers can produce silicone rubber products with exceptional thermal endurance, reliable mechanical properties, and excellent processing characteristics. We are committed to providing the quality chemical auxiliaries and expertise needed to unlock the full potential of silicone rubber applications.