A new study by HSLL researchers, published in npj Heritage Science, sheds new light on the acidic emissions produced during the degradation of poly(vinyl chloride) (PVC), a material widely found in heritage collections. In the paper titled “Poly(vinyl chloride) degradation: Identification of acidic degradation products, their emission rates and implications for heritage collections”, Špela Pok, Irena Kralj Cigić, Matija Strlič and Tjaša Rijavec improved the understanding of acidic emissions from heritage PVC, quantified the emission rate of HCl and evaluated the risk of its emission at room temperature. The results showed that HCl emissions at room temperature are too low to meaningfully and significantly contribute to the pollution of the environment in which heritage collections are displayed and stored.

The authors reported a first study establishing the methodology for assessment of the degradation of PVC by measuring HCl emission rates. They observed a two-phase HCl emission pattern – an initial rapid release likely due to trapped HCl, followed by sustained emission from ongoing degradation. This finding provides new insights into PVC emission dynamics and may inform future testing protocols.

The study also revealed that degrading PVC emits formic and acetic acid, with acetic acid present in the highest quantities. Its emissions showed a clear correlation with damage observed in cross-infection tests on reference cellulose, indicating it plays a more damaging role in enclosed environments.

“Our results suggest that while HCl is a known degradation product, acetic acid is a more relevant risk in heritage contexts,” the authors conclude. “These findings have important implications for storage and display strategies of PVC-containing objects.”

The article can be found at: https://doi.org/10.1038/s40494-025-01955-w

Mikrochambers used to study the degradation of PVC by measuring HCl emission rates.