Detail

Benzoyl peroxide (BPO) can be used

Time：2022-08-31source：Taizhou Longyu Chemical Co., Ltd

The polymerization process of polystyrene is a free radical chain reaction, but unless extreme conditions are used, it is difficult to form initial free radicals from stable styrene molecules. This is where an initiator (like benzoyl peroxide) needs to be added. Benzoyl peroxide (BPO) can break the weak O-O bond (fission occurs because the two oxygen atoms have the same electronegativity) to generate two benzoyl radicals.

A "dot" next to an atom indicates that there are unpaired electrons there, which is why free radicals are so reactive, they try to find another free radical to pair with, creating a covalent bond. These benzoyl groups then eliminate the CO2 forming the phenyl group. Because stable molecules become reactive free radicals, this is called the initiation step, and it triggers the formation of free radicals.

Although benzoyl peroxide (BPO) generates only a small amount of phenyl groups during the reaction, once formed, they can interact with the styrene monomer during the propagation step. One free radical disappears, but is replaced by another free radical, so the free radical "propagates" in the chain reaction.