A radical initiator is a substance that generates free radicals, which can initiate free radical polymerization. Radical initiators typically decompose upon heating or exposure to UV light to produce free radicals. These radicals then react with monomers to start the growing chain. Common examples of radical initiators include peroxides (e.g., benzoyl peroxide) and azo compounds (e.g., AIBN).

自由基引发剂是产生自由基的物质，可以引发自由基聚合。自由基引发剂通常在加热或暴露于紫外光时分解产生自由基。然后这些自由基与单体反应以开始不断增长的链。自由基引发剂的常见例子包括过氧化物（例如过氧化苯甲酰）和偶氮化合物（例如 AIBN）。