Advanced non-invasive fluorescence spectroscopy and imaging for mapping photo-oxidative degradation in acrylonitrile-butadiene-styrene: A study of model samples and of an object from the 1960s

Complementary use of fluorescence multispectral imaging and fluorescence lifetime imaging (FLIM) for the assessment of the degradation of a historical design object made in acrylonitrile-butadiene-styrene (ABS) is demonstrated. Model samples of ABS, exposed to UV irradiation to simulate photodegradation, have been analysed with fluorescence spectroscopy and fluorescence lifetime spectroscopy. Results demonstrate rapid modifications of the picosecond and nanosecond fluorescence lifetimes following short irradiation times, which are accompanied with significant modifications in fluorescence excitation-emission spectra. Changes in spectra and lifetimes in samples are ascribed to the accumulation of α,β unsaturated aldehydes and α,β diketones and the loss of volatile organic components (including acetophenone). Complementary analyses of samples with Fourier transform infrared spectroscopy suggest that modifications in fluorescence are correlated with photo-oxidative degradation of ABS. Fluorescence lifetime and fluorescence multispectral images of the Grillo telephone (1965) made in ABS were acquired. Analysis of images allowed the rapid mapping of differences in fluorescence which are attributed to heterogeneous degradation on the object surface. Implications for the assessment, monitoring and conservation of objects in ABS and other polymers are suggested.