Initiation (chemistry)

Thermal initiation

Thermal initiation involves initiating a reaction in the presence of heat, usually at very high temperatures. Heating a reaction can result in radical initiation of the substrate(s). In the presence of heat, a monomer can self-initiate and react with other monomers or pairs of monomers. This process is called spontaneous polymerization and requires a lot of heat to occur (up to 200 °C). For monomers to initiate and polymerize with the same type of monomer (called Homopolymerization), ~180 °C is needed for the monomers to initiate. Copolymerization, which is when different kinds of monomers are initiated and react with each other, is more stable and can happen at lower temperatures than Homopolymerization. Self-initiation between homo-monomers is a difficult mechanism to observe because species that are initiated aren't always the same kind of monomer. Sometimes impurities found in the reaction flask with the monomers get initiated and polymerize with monomers, instead of the monomer getting initiated.