Thermal Degradation of Some Thermoplastic Polymers in Presence of Lignin

Degradation of polymers is a very important reaction in the chemistry of high molecular mass compounds. It occurs under the action of chemical agents or as a result of physical influences. On using a small percent of lignin in the thermal depolymerization of a polymer, such as polystyrene or polymethyl methacrylate, a significant enhancement in the rate of degradation was observed. The yield obtained was comparable to that obtained on using zinc dust or ferrous sulfate in a percent amounting to that of lignin. The role of lignin in enhancing the monomer yield on thermal degradation of polymer is its action as inhibitor on the chain process in analogy with the chain polymerization. On the other hand, the role of zinc dust and ferrous sulfate in enhancing the rate of polystyrene degradation is through the increased decomposition of the intermediate hyperperoxide which leads to more free radicals and hence to a larger increase in the rate of degradation.