Differences between condensation and addition curing RTV-2 silicone rubbers

Condensation curing rtv-2 silicone rubber

Typical catalysts for condensation curing are dibutyltin dilaurate and dibutyltin octoate. They catalyse the reaction between a, w - dihydroxypolydimethylsiloxanes and silicic acid esters. Water has a strong accelerating effect on the rate of reaction. The rate of reaction also depends on the crosslinking agent (its functionality, concentration and chemical structure) and on the type of catalyst. Unlike organic latexes and rubbers, no sulfur is used for curing silicone rubbers.

1-Blending ratio of silicone rubber and catalyst variable within limits
2-Crosslinker agent and catalyst are both contained in the catalyst
3-Curing impaired only by lack of water
4-Curing rate largely independent of temperature
5-Chemical shrinkage due to release of alcohol
6-Release products (alcohol) may cause reversion from 80 °C and above
7-Long pot life and hence long curing times

Addition curing rtv-2 silicone rubber

Addition curing functions by attaching Si-H groups to double bonds. Salts or complexes of platinum, palladium or rhodium may serve as catalyst. If platinum-olefin complexes are used, curing will take place at room temperature. Platinum complexes containing nitrogen are used for effecting addition curing at elevated temperatures (e.g. Pt-complexes with pyridine, benzonitrile or benzotriazole).

1-Blending ratio of silicone rubber and catalyst variable within limits
2-Crosslinker agent and catalyst are both contained in the catalyst
3-Curing impaired only by lack of water
4-Curing rate largely independent of temperature
5-Chemical shrinkage due to release of alcohol
6-Release products (alcohol) may cause reversion from 80 °C and above
7-Long pot life and hence long curing times