Online monitoring of the influence of the chemical structure of hindered amines on the hydrolysis of polycarbonate in a polycarbonate/poly(acrylonitrile–butadiene–styrene) blend by ultraviolet–visible spectroscopy

Abstract

AbstractWithout stabilization, polycarbonate (PC)/poly(acrylonitrile–butadiene–styrene) (ABS) blends are susceptible to a loss of mechanical properties after a few days of exposure to weathering conditions. ABS can be stabilized against terrestrial light by the use of hindered amines in combination with a UV absorber; such hindered amines cannot be used when PC is present in the polymer blend. The hydrolysis of PC is accelerated when a small amount of a hindered amine light stabilizer (HALS) is incorporated into the resin and is exposed to elevated temperatures. In this study, three different HALSs (Tinuvin 123, Tinuvin 770, and Tinuvin 765, Ciba, Basel, Switzerland) were used as UV stabilizers for PC/ABS blends, and their effects on the PC phase were observed with online ultraviolet–visible spectroscopy on extruded flat films. These stabilizers were compounded with the blends in a corotating twin‐screw extruder at 240°C. The molecular weight of the compounded samples was determined by gel permeation chromatography. The extent of degradation induced by the HALSs on the PC phase was found to be a function of its chemical structure. Tinuvin 123 with an amino ether functional group enhanced degradation in comparison with Tinuvin 770 and Tinuvin 765. Tinuvin 770, a secondary amine, was apt to be more reactive than Tinuvin 765, a tertiary amine, because less steric hindrance was experienced by the former. Accelerated aging of the compounded samples was performed. Decreased degradation was observed for the samples containing hindered amines; however, the HALSs alone were not effective in protecting the PC/ABS blends against harmful UV light. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011