The weathering study of PC/ASA alloy for automotive exterior applications

Abstract

Polycarbonates (PC) are used in automotive industry due to their high physical and mechanical properties like high impact resistance and ductility. Polycarbonates are blended with ABS (Acrylonitrile-Butadiene-Styrene) and ASA (Acrylonitrile-Styrene-Acrylate) terpolymers for interior and exterior applications of automotive components to achieve good physical and mechanical properties. Other reason for choosing such alloys for interior applications is the IZOD impact resistance requirement higher than 40 kJ/m2. Recently, grades of PC/ASA with UV stabilization are developed for non-painted exterior applications. The aim of our study is to investigate whether new developed PC/ASA could be chosen for exterior applications of automotive industry. In this study, the samples are prepared from injection molding and the weathering performance of PC/ASA was tested by a weather-o-meter for 1500 h at a total of 1890 kJ/m2 at 340 nm with a cut-off filter at λ<290 nm. The results are evaluated by FT-IR, DSC, TGA, and SEM. It has been observed that UV degradation of PC/ASA leads to several major changes in its IR spectrum like broad bands occurring in the hydroxyl region around 3300 cm-1, and carbonyl stretching region increased intensity around 1728 cm-1. The main degradations were based on photo-oxidation and photo-Fries rearrangement of PC. In our study, the photo-oxidation was followed by the color shift to yellowing of the polymer.