Explanation

monomer can produce active free radicals through the action of light, heat, radiation or initiator, which can initiate chain polymerization reaction. In this chain polymerization, initiator is the key component, which forms primary free radicals through addition reaction with monomer. The decomposition of initiator is an endothermic reaction, which requires high energy. Once primary free radicals are formed, they will continue to react with other monomer to form new free radicals, which have more structural units. This process is called chain growth reaction. chain growth reactions have low activation energy, so they occur very quickly. chain termination is another key step in chain polymerization, in which free radicals lose their activity. The chain termination reaction can occur through coupling termination or disproportionation termination termination. Compared with chain growth reaction, the activation or conditioning energy of chain termination reaction is very low, sometimes even close to zero. The mechanism characteristics of traditional free radical polymerization include slow initiation, fast growth, fast termination and possible chain transfer. The reaction rate is affected by many factors, including free radical concentration, monomer concentration, initiator system, impurities, reaction medium and temperature. Generally, organic or inorganic peroxides and azo compounds are commonly used initiator. The main monomer of polymerization include ethylene monomer and conjugated monomer. free radical polymerization plays an extremely important role in polymer chemistry. Many polymer, such as polyethylene, polypropylene, polymethyl methacrylate, polyacrylonitrile, polyethylene acetic acid, styrene butadiene rubber, acrylonitrilebutadiene rubber and chloroprene rubber, are synthesized through free radical polymerization.

Classification