ThermalInitiatoren

Thermal initiators are chemical compounds that decompose upon heating to generate reactive radicals, which start polymerization or cross-linking reactions. They provide a source of radicals without reliance on light or redox triggers, making them suitable for processes conducted at elevated temperatures or in bulk.

The decomposition of thermal initiators is governed by kinetics that depend on temperature. Common classes include azo initiators (such as azobisisobutyronitrile, AIBN, and water-soluble VA-044) and hydroperoxide or peroxide initiators (for example benzoyl peroxide, tert-butyl peroxide, and dicumyl peroxide). Upon heating, these compounds cleave bonds to form radicals that propagate polymerization. The half-life of an initiator at a given temperature is a key parameter, often used to control polymerization rate and molecular weight. Safety considerations arise from the exothermic and gas-evolving nature of radical formation, which can lead to runaway reactions if poorly controlled.

Typical applications include bulk, solution, and emulsion polymerizations, as well as curing of coatings, adhesives, and cast resins. Thermal initiators are often chosen for processes where light access is limited or where initiation needs to occur throughout a bulk material. They can be used alone or in combination with inhibitors to prevent premature polymerization during storage and handling.

Handling and storage require attention to temperature and containers, as many initiators are sensitive to heat, shock, and contaminants. Inhibitors such as hydroquinone or BHT are commonly used to suppress premature polymerization in storage. Proper storage in cool, dry conditions minimizes degradation and ensures predictable initiation behavior during processing.