本发明系关于一种悬浮聚合苯乙烯单体以制造聚苯乙烯之方法，其包括下列步骤：(a)加热包含苯乙烯单体之聚合悬浮液至温度为至少60℃，(b)在聚合反应期间，于大于90分钟至小于5小时之期间内以连续方式或间歇性地以至少两部份将引发剂定量至该经加热之聚合悬浮液中，该期间始於单体转化率小于65%时且该引发剂在其定量之温度下具有不大于60分钟之半衰期，其中在聚合反应期间该聚合悬浮液中存在溴化阻燃剂。

A process for the suspension polymerization of styrene monomer to produce polystyrene comprising the steps of (a) heating a polymerization suspension comprising the styrene monomer to a temperature of at least 60 DEG C, (b) dosing an initiator to said heated polymerization suspension during the polymerization reaction over a period of more than 90 minutes to less than 5 hours, in a continuous manner or intermittently in at least 2 portions, said period starting at a monomer conversion of 65% of less and said initiator having a half-life at the temperature at which it is dosed of not more than 60 minutes, wherein a brominated flame retardant is present in the polymerization suspension during the polymerization reaction.