A new insight into polyurethane foam deterioration: the use of Raman microscopy for the evaluation of long-term storage conditions

This research aims at bringing new contributions for lowering the polyether-based polyurethane (PUR) flexible foam high deterioration rate by studying selected storage conditions. With a life expectancy of 20–50 years, many PUR objects show severe deterioration signs that, so far, cannot be prevented. To establish a preservation strategy, a natural ageing experiment in the dark (12 months, 45–55% relative humidity) has been carried out for the study of four storage conditions: open air at room temperature (T) and sealed enclosures at room T (with/without oxygen) and low T (11–13 °C). For this research, unaged (model PUR) and naturally pre-aged (commercial PUR) references were included. The samples were analysed every 3 months by colourimetry, optical microscopy (visible and UV light), infrared and Raman microspectroscopies. Further statistical data treatment was carried out in order to identify significant spectral variations (ANOVA) and to uncover correlations between molecular spectral lines and physical aspects. Raman proved to be a powerful tool in the detection of early stage PUR molecular deterioration. For both model and commercial samples, open-air storage proved to be the most harmful condition, while anoxic storage showed the best results. In general, this experiment has enabled new contributions for lowering PUR high deterioration rate.