Stabilization of polypropylene

The effectiveness of polyproylene antioxidant systems in other than a simple oxidative environment has been studied. For example, it has been found that contact of stabilized propylene polymers with a number of materials, particularly with plasticized poly (vinyl chloride) and with copper and copper salts, markedly decreases the resistance of the composition toward oxidative degradation. The use of antioxidants having higher molecular weights results in improved retention of stabilization when polypropylene is used in contact with materials such as plasticized poly (vinyl chloride), presumably because partition of the antioxidant from the polypropylene composition is decreased. Antioxidant effectiveness in polypropylene compositions in contact with copper can be greatly increased by the addition of new and more effective copper inbibitors. The usefulness of copper compleming agents such as hydrazides, triazoles, tetrazoles, and derivatives of malonamide and oxamide are compared in polypropylene compositions containing copper dust and antioxidants.