Differences Between Condensation-Cure and Addition-Cure Silicone Rubber
Condensation-cure and addition-cure silicone rubber are two common types of liquid silicone rubber, each with distinct characteristics. Below is a detailed comparison between the two types:
1. Curing Mechanism
Condensation-Cure Silicone Rubber:
This type cures through a condensation reaction, where reactive groups condense and release small molecules (such as water or alcohol), forming cross-linked structures. The curing process may be influenced by humidity, as moisture can accelerate the reaction.
Addition-Cure Silicone Rubber:
The curing of this type is based on a hydrosilylation reaction, where a silicon-hydrogen bond reacts with a vinyl or allyl group, resulting in cross-linking without producing small molecular by-products. This ensures minimal shrinkage after curing, and the reaction can take place at room temperature without the need for external heating.
2. Performance Characteristics
Condensation-Cure Silicone Rubber:
Strength: Relatively lower mechanical strength but exhibits good adhesion.
Curing Speed: Affected by humidity, with faster curing in high humidity environments.
Shrinkage: Relatively high, which can affect the dimensional accuracy of the final product.
Toxicity: Catalysts used in condensation-cure silicone may contain harmful substances, requiring proper safety precautions during use.
Cost: Lower in cost, making it suitable for general industrial applications.
Addition-Cure Silicone Rubber:
Strength: Higher mechanical strength and forms a soft, transparent, or semi-transparent elastomer after curing.
Curing Speed: Not affected by humidity, and curing speed can be increased by heating.
Shrinkage: Minimal, enabling deeper vulcanization and higher dimensional accuracy in finished products.
Toxicity: Uses platinum-based catalysts, which are non-toxic and odorless, making it suitable for food-grade and medical-grade applications.
Cost: Higher cost but offers superior performance, ideal for applications requiring high-quality materials.
3. Application Areas
Condensation-Cure Silicone Rubber:
This type is commonly used in mold-making, industrial goods, electrical and automotive parts. Its lower cost and ease of processing make it widely applicable in these sectors.
Addition-Cure Silicone Rubber:
More frequently used in silicone kitchenware, silicone toys, silicone gifts, and high-end fields such as medical products. The superior performance of addition-cure silicone rubber makes it indispensable in these areas.
4. Environmental Impact
Both types of silicone rubber are environmentally friendly, but addition-cure silicone rubber has a higher environmental standard. It can pass FDA testing and obtain certifications like ROHS, making it suitable for food-grade and medical-grade applications.
Condensation-cure and addition-cure silicone rubber differ significantly in terms of curing mechanism, performance characteristics, application areas, and environmental impact. When choosing which type to use, it is essential to consider specific application needs and performance requirements.