STABILIZATION OF HIGH-DENSITY POLYETHYLENE

Several types of antioxidants are evaluated in high‐density polyethylene for color and physical property stabilization during processing and thermal aging. A wide variety of evaluation tests are used and discussed. Heat‐ and light‐induced oxidation mechanisms are reviewed. Antioxidants such as octadecyl‐3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) propionate and tetrakis[methylene 3‐(3′,5′‐di‐tert‐butyl‐4′‐hydroxy phenyl) propionate] methane were found to provide very high retention of physical properties, excellent initial color and color retention. Combinations of antioxidant‐ and ultraviolet light absorbers were evaluated for stabilizing high density polyethylene exposed to artificial light and outdoor weathering. The combination of octadecyl‐3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) propionate and 2‐(2′‐5′‐di‐tert‐butyl‐2′‐hydroxy‐phenyl)‐5‐chlorobenzotriazole was found to be a very efficient stabilizer system. Polymer containing this stabilizer combination had excellent color stability and minimum crosslinking and embrittlement after Arizona weathering. Copyright © 1968 John Wiley & Sons, Inc.