'Phosphite-Free' Stabilization of Polyolefins

Abstract

Deficiencies of present anti-oxidant (AO) systems led to our initiating a series of studies with 'phosphite-free' AO systems based on catocopherol (vitamin E) formulations. This study evaluated the effects of several AO systems on the yellowness index (YI), melt flow rate (MFR) and on gel formation after five to eight passes of two types of high density polyethylene (HDPE) and four types of polypropylene (PP) resins through an extruder. It was demonstrated that the a-tocopherol can replace phenolic/phosphite combination as the primary AO system; or the a-tocopherol formulations can simply replace the phosphite portion to achieve better performance. In either case, the problems associated with phosphites can be eliminated or minimized by the ca-tocopherol AO; and usually at a lower cost.