Fluorescence and Fourier-transform infrared spectroscopy for the analysis of iconic Italian design lamps made of polymeric materials

The preservation of design object collections requires an understanding of their constituent materials which are often polymeric blends. Challenges associated with aging of complex polymers from objects with an unknown physical history may compromise the interpretation of data from analytical techniques, and therefore complicate the assessment of the condition of polymers in indoor museum environments. This study focuses on the analysis of polymeric materials from three well-known Italian design lamps from the 1960s. To assess the degree of chemical modifications in the polymers, non-destructive molecular spectroscopic techniques, Fourier-transform infrared (FTIR) and fluorescence spectroscopy, have been applied directly on the object surfaces using an optical fiber probe and through examination of micro samples. FTIR spectra of the different polymers, polyvinylacetate (PVAc) for the lamps Taraxacum and Fantasma, and both acrylonitrile-butadiene-styrene polymer (ABS) and cellulose acetate (CA) for the lamp Nesso, allowed the detection of ongoing deterioration processes. Fluorescence spectroscopy proved particularly sensitive for the detection of molecular changes in the polymeric objects, as the spectra obtained from the examined lamps differ significantly from those of the unaged reference materials. Differences in fluorescence spectra are also detected between different points on the same object further indicating the presence of different chemical species on the surfaces. With the aid of complementary data from FTIR spectroscopy, an interpretation of the emission spectra of the studied polymeric objects is here proposed, further suggesting that fluorescence spectroscopy may be useful for following the degradation of historical polymeric objects.