Photo‐oxidation of polypropylene films. VI. Possible UV‐stabilization mechanisms

Abstract

Abstract The effects of the chemical nature, concentration, stability, and location of various additives on the ultraviolet stability of polypropylene are discussed. It is shown that effective stabilizers of thin films do not depend on UV absorption for their protective action, whereas some relatively inefficient additives operate solely as UV screeners. Adequate UV protection was observed when small amounts (∼0.01 wt‐%) of effective stabilizers were concentrated in or on the surfaces of commercial films, and the remaining bulk of the film contained only a very low concentration (∼0.01 wt‐%) of uniformly blended additive. Previous attempts at demonstrating energy‐transfer stabilization of the polymer are discussed with reference to the present data; it is concluded that effective polypropylene stabilizers probably operate by a combination of chromophore quenching, radical scavenging, and hydroperoxide decomposition.