How does temperature affect vulcanization?
Temperature is the most important lever when processing silicone rubber. It determines how long a mix remains workable (pot life) and how quickly it cures. Data sheet values usually refer to standard climate (23 °C, 50 % relative humidity).
Addition-curing two-part silicones
- Heat strongly accelerates crosslinking – cure times can be cut from hours to minutes. ELASTOSIL RT 602 A/B cures very quickly with heat; ELASTOSIL RT 625 A/B cures quickly and without shrinkage.
- Cold slows curing considerably; below room temperature it may remain incomplete.
- A warm workshop or warm material shortens pot life. WACKER INHIBITOR PT 88 can extend it in a controlled way.
- One-part heat-curing silicones such as SEMICOSIL 989/1K only crosslink at elevated temperature – ideal for automated processes.
Condensation-curing two-part silicones
- Cure speed is mainly set by the type and amount of hardener, e.g. fast with WACKER Härter T 47 or WACKER Härter T 77.
- Low temperatures and very dry air slow the reaction.
- Do not heat parts strongly in closed volumes before they are fully cured.
One-part silicones (RTV-1)
RTV-1 adhesives and sealants such as ELASTOSIL E43 cure with atmospheric moisture from the surface inwards. Warm, humid air speeds up curing; cold, dry air slows it down. Thick layers take correspondingly longer.
Practical tips
- Bring material and parts to room temperature before processing.
- In series production keep the temperature constant so that pot life and cycle time stay reproducible.
- Always validate new process parameters with a preliminary test.
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