THERMAL-OXIDATION OF EXTRUDED POLY(2,6-DIMETHYL-1,4-PHENYLENE OXIDE)

The oxidation of extruded polyphenylene ether resin at moderate temper atures has been shown to obey Arrhenius kinetics with first-order depe ndence on the hydroxyl endgroups and half-order dependence on oxygen. In blends, the oxidation is overall second order in uncapped resin. Th e phenolic endgroup catalyzes the oxidation of the benzylic methyl gro ups, so capping the resin leads to a much reduced oxidation rate. The rate of oxidation of the capped commercial resin is approximately the same as that of pure capped model compounds, showing that other factor s such as residual catalyst or structural irregularities play only a m inor role in promoting the oxidation. A mechanism involving attack of the endgroup phenoxyl radical on the benzylic methyl group is suggeste d as the first step in the oxidation of the uncapped polymer.