Two-component room temperature vulcanization silicone is divided into two types of condensation silicone rubber and addition silicone rubber, many users who make silicone molds do not know which one to choose is suitable, the following will explain the difference between condensation silicone and addition silicone.
1. Principle of Vulcanization
Condensed silicone rubber is the most common kind of rtv silicone rubber, where part A is viscous liquid silicone, part B is an organic tin curing agent, the current market condensed silicone rubber ratio is usually 100:2 to 100:4, After AB is mixed, the silica gel and the curing agent undergo a cross-linking reaction, and small molecules are precipitated during the curing process.
The principle of curing of addition silicone rubber is based on the addition reaction (hydrosilation reaction) between the vinyl (or propylene) group on the end group of the methyl vinyl silicone rubber (green rubber) and the silicon hydrogen group on the crosslinker molecule. In this reaction, the hydride functional polysiloxane is used as a crosslinker (vulcanizing agent) and chloroplatinic acid or other soluble platinum compounds are used as catalysts.
2. Applications
Condensed silicone rubber is mainly used for silicone mold making of industrial-grade products, the use method can choose pour or brush, widely used for silicone mold making of crafts, plaster, garden sculpture, cement products, concrete, toys and gifts and other products.
Addition silicone rubber is mainly used for the production of food-grade or high-precision silicone molds., suitable for pour-on operation process, such as soap, candles, chocolate, cakes, candy silicone mold making, and silicone insoles, adult products silicone products making.
3. Feature Comparison
| Condensation Silicoen Rubber | Addition Silicone Rubber | |
|---|---|---|
| AB Ratio | 100:2~100:4, white or translucent | 1:1 or 10:1, translucent or transparent |
| Curing Method |
Normal temperature curing, influenced by thickness and temperature |
Curing at room temperature or heating, not affected by thickness |
| Temperature Resistance | General temperature resistance, easy to age at high temperatures | Good temperature resistance, suitable for baking in the oven |
| Curing Agent | Tin curing agent, compatible with most materials | Platinum agent, with acid and alkali materials will not be cured |
| Odor | Slightly odorous | Non-toxic and odorless |
| Hardness | 5-40 Shore A range | 30 Shore C - 50 Shore A ranging |
| Shrinkage | About three thousandths | About one thousandth |
| Security Level | Industrial grade | Food grade |
| By-product | There are small molecules precipitated | No by-products |
| Cost | Relatively lower | Relatively higher |