Spatial effects in the photodegradation of poly(acrylonitrile–butadiene–styrene): a study by ATR-FTIR

Abstract

Spatial effects in the degradation of poly(acrylonitrile–butadiene–styrene) (ABS) exposed to UVB radiation (λ=290–330nm) and oxygen in a weathering chamber at 318K were studied by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The polymer contained 2wt% Tinuvin 770, a hindered amine stabilizer (HAS). ABS samples of thickness 4mm were irradiated, microtomed, and sections of thickness 50 and 150μm were studied as a function of treatment time. ATR-FTIR profiling indicated that the degradation was spatially heterogeneous: significant amounts of photoproducts were detected only in the directly irradiated layer of depth ≈50μm. In this layer, major damage was reflected in the appearance of the hydroxyl (3600–3200cm−1) and the carbonyl (1800–1600cm−1) peaks, and in the disappearance of the 967cm−1 peak from 1,4 butadiene units (1,4 PB). The hydroxyl and carbonyl peaks were also detected in the second layer of thickness ≈50μm. Slight changes in the intensity of peaks in the above three spectral regions, compared to a nonirradiated reference sample, were also detected on the nonexposed sample side, and assigned to thermal degradation. For irradiation times up to ≈2000h, the spectra indicated damage of the butadiene structure, and no changes in the styrene–acrylonitrile (SAN) matrix. The present study confirmed major conclusions deduced from 1D and 2D nondestructive electron spin resonance imaging (ESRI) experiments performed on the same samples in our laboratory, and provided additional information on the spatial distribution of stable degradation products.