Noninvasive Monitoring of Polycarbonate Mechanochemical Properties under Broad-Band Photodegradation

A noninvasive vibrational spectroscopy approach is proposed to monitor the conservation state of historical polycarbonate (PC) design and heritage objects, with the aim of identifying early signs of degradation essential for effective preservation. Systematic investigations on reference PC samples, artificially aged under indoor and outdoor lighting conditions, using IR external reflection spectroscopy, enabled the noninvasive tracking of both photo-Fries rearrangement and photo-oxidation, the two well-known degradation pathways of PC. Since mechanical loss is a key issue in plastics, the correlation between chemical and mechanical properties was further investigated by combining IR spectroscopy with Brillouin light scattering (BLS). This correlative analysis provided a novel noninvasive analytical tool for monitoring the mechanochemical changes underlying yellowing and embrittlement, linking PC molecular degradation to its altered viscoelastic behavior. Although originally designed for use in cultural heritage studies, the proposed approach establishes a framework for evaluating and monitoring a wide range of polymeric materials across diverse industrial applications. By bridging the gap between fundamental preventive conservation and polymer science, it supports strategies aimed at safeguarding both cultural heritage and modern technological materials.