There are two main types of curing systems used in silicone rubber production — peroxide curing and platinum curing. Each has distinct chemical mechanisms, advantages, and application fields.
Peroxide curing agents (such as dicumyl peroxide or benzoyl peroxide) work by thermal decomposition, releasing free radicals that promote crosslinking between silicone polymer chains. This method is widely used for high-temperature vulcanized (HTV) or high-consistency rubber (HCR) silicone.
Advantages: Cost-effective, strong mechanical properties, good heat resistance.
Applications: Industrial seals, automotive parts, electronic components, and general-purpose silicone products.
Limitations: May produce by-products or odors during curing; not suitable for food-grade or medical-grade applications.
The platinum-catalyzed curing system is a addition-type reaction, where the curing agent enables Si–H and vinyl groups to form crosslinks without generating by-products. This system is primarily used for liquid silicone rubber (LSR) or high-purity silicone materials.
Advantages: Non-toxic, odorless, and environmentally friendly. It offers excellent transparency, flexibility, and stability.
Applications: Baby products, kitchenware, food-contact parts, and medical devices.
Limitations: Higher cost, sensitive to contaminants (such as sulfur, nitrogen compounds, or amines) that may inhibit curing.
In addition to the two main systems, there are also condensation-type and UV-curing systems used in specific fields.
Condensation curing: Common in room-temperature vulcanizing (RTV) silicone, such as sealants and adhesives.
Selecting the proper curing agent is a critical step in silicone product manufacturing. The right choice ensures not only the desired performance but also compliance with safety and regulatory standards. Several key factors should be considered:
The end use of the silicone product determines the suitable curing system.
Food-grade, baby, or medical silicone must use platinum curing, as it guarantees purity, no odor, and no harmful by-products.
Industrial and automotive components can use peroxide curing, which provides excellent mechanical strength and cost efficiency.
The production process also affects the curing choice.
Liquid Silicone Rubber (LSR) molding typically requires platinum curing, due to its fast, clean reaction and precise molding properties.
High-Consistency Rubber (HCR) can be processed with peroxide or platinum curing, depending on the target quality and cost.
If the product demands high transparency, low shrinkage, or long-term stability, addition (platinum) curing is the best choice.
For applications that prioritize toughness, heat resistance, or lower cost, peroxide curing remains the most practical solution.
Curing agents must meet FDA, LFGB, and RoHS standards for silicone products that contact food or skin. Therefore, understanding the customer’s market and regulatory requirements is essential before selecting a curing system.
If you are looking for manufacturers of silicone products, you often hear that there is a process of secondary vulcanization. So, what does "secondary vulcanization" mean? What's the purpose?
Secondary vulcanization refers to the post-curing process carried out after the initial molding and primary curing of silicone rubber.
While the first curing step shapes the silicone, there may still be residual curing by-products, volatile substances, or unreacted compounds left in the material.
Through secondary vulcanization — typically done in an oven at 180–220°C for 2–4 hours — these residues are removed, and the silicone’s internal crosslinking network becomes more complete.
Remove Residuals and Odor
Eliminates peroxide by-products or other volatile compounds, resulting in a cleaner, odorless silicone.
Enhance Mechanical Strength
Improves tensile strength, tear resistance, and elasticity.
Improve Heat and Aging Resistance
Post-cured silicone performs better under continuous high-temperature use.
Ensure Food and Medical Safety
Essential for food-grade and medical-grade silicone to meet international standards (FDA, LFGB, etc.).
In short, secondary vulcanization ensures that the silicone product is stable, safe, and ready for end use, especially when high performance or purity is required.
This is why the products of some factories are a little more expensive than those of others. In some cases, omitting the secondary vulcanization can save costs. However, if one is a brand owner, they would prefer to keep their products in the best condition in front of consumers.
