The Effect of Weathering on the Flow, Microstructure and Physico-mechanical Properties of ABS.

The effects of weathering on the flow, microstructure, and physico-mechanical properties of an unstabilized poly(acrylonitrile-butadiene-styrene) (ABS) were investigated by irradiating the ABS samples with a wavelength distribution comparable to solar light at 45°C and relative humidity of 50 percent. A series of ABS samples were prepared by melt mixing of SAN and high rubber content g-ABS. All specimens were characterized by melt flow index (MFI) measurements, heat distortion temperature (HDT), Fourier transform infrared spectroscopy (FTIR), impact strength (Izod), tensile testing and measuring of CIEL*a*b* colour components (data of L*,a*,b* and YI). Alteration in the flow and physical properties was observed. The samples underwent extensive reduction in Izod impact strength, elongation-at-break, workto- break, and turned yellow upon irradiation. The MFI, HDT, and FTIR results showed that upon weathering of ABS, cross-linking and chain scission of rubber phase were the governing degradation and yellowing mechanisms. The loss of unsaturation (disappearance of 1,4-polybutadiene) and alteration in carbonyl group as well as the hydroxyl group were observed. Significant amounts of photoproducts were detected in the directly irradiated surface layer. The colour difference of yellowing (delta)YI exhibits a systematic tendency to higher values with increasing irradiation time.