Plasticizer Migration in Plasticized PVC: Experimental and Molecular Insights Relevant to Heritage Conservation

Plasticized poly(vinyl chloride) (PVC) is widely represented in modern heritage collections, yet its long-term stability is strongly affected by plasticizer migration, evaporation, and surface accumulation. This study uses model plasticized PVC films to examine how the molecular structure of common plasticizers (DBP, DEHP, DINP, and DOTP) controls retention and degradation behavior relevant to conservation. Accelerated aging experiments combined with ATR-FTIR, NMR, and UV–Vis spectroscopies showed that neat plasticizers are thermally stable under dry conditions, although DBP is especially vulnerable to hydrolysis under elevated humidity. In model PVC films, DBP was lost most rapidly, DEHP showed intermediate retention, whereas DINP and DOTP were retained more effectively. Density functional theory (DFT) and molecular dynamics (MD) calculations provide molecular-level insight into these trends, indicating that DBP, DEHP, and DOTP are preferentially stabilized at the PVC surface, promoting migration, while DINP is more stable when embedded between PVC chains. Energy decomposition analysis (ETS-NOCV) identifies dispersion interactions as the dominant factor governing plasticizer-PVC compatibility, with interaction strength increasing in the order DBP < DEHP < DOTP ≈ DINP. These findings are supported by large-scale MD simulations, which confirm the surface affinity of DOTP in extended polymer systems. The combined experimental and theoretical approach elucidates the mechanisms underlying plasticizer migration and retention, improves the prediction of material behavior, and helps museum professionals identify potentially endangered PVC-based cultural heritage objects.