Synthesis of Polyethylene-Grafted Phosphite Antioxidant and Its Antioxidant Behavior in Polypropylene

A novel macromolecular auxiliary antioxidant with polyethylene (PE) as polymer skeleton and phosphites as side groups is prepared based on commercial ethylene-vinyl acetate (EVA) copolymers and its potential as polyolefin stabilizers is studied in depth. The synthesis approach of this PE-grafted antioxidant consists of a typical EVA hydrolysis reaction and a two-step nucleophilic substitution reaction of PCl 3 , 2,4-di-tert-butylphenol, and the hydrolysis product. Results of the thermogravimetric analysis show that the macromolecular structures endow the as-synthesized antioxidant with much better thermal stability than that of the commercial antioxidant 168. In addition, antioxidant behaviors of the PE-grafted antioxidants in polypropylene (PP) matrix are investigated in detail through characterization of the melt flow index of multiple-extruded stabilized PP as well as the short-term oxidation induction time test and the long-term thermo-oxidative aging test. Results show that even with extremely low content of the effective antioxidant groups, the as-synthesized macromolecular antioxidant still has excellent antioxygenic properties.