Clay-induced degradation during the melt reprocessing of waste polycarbonate

Abstract

The addition of small amounts of organoclays during the reprocessing of waste polycarbonates (WPCs) is a promising method for improving the properties of the recycled plastics. However, the clays can also induce the degradation of the polymer during the melt compounding and thus lower the properties of the final materials. This clay-induced degradation of polycarbonate (PC) was examined in this study. A WPC, a virgin PC (VPC) (that served as a comparison), and two commercial montmorillonites, Cloisite 15A and Cloisite 30B, were melt compounded in a twin-screw microextruder. The degradation of the polymer, which caused the formation of phenolic compounds and the reduction of the average molar mass, was monitored with UV spectroscopy, thermogravimetric (TG) analysis, and solution viscosimetry. The results reveal that the effect of the clays on the degradation depended on the amount of clay used and the chemical nature of the organic modification. When small amounts of the appropriate clay were used, the polymer degradation was minimized, and a net improvement of some properties of the recycled PC was achieved.