Inhibiting the deterioration of plasticised poly (vinyl chloride) in museum collections

Plasticized poly (vinyl chloride) (PVC) is found in museum collections as three dimensional objects and as packaging materials. Many PVC materials deteriorate within 25 years of acquisition. Migration and chemical breakdown of plasticizer, accompanied by dehydrochlorination of the polymer are the major mechanisms of deterioration.

The extent, rate and mechanisms of deterioration of new and naturally aged PVC containing di (2-ethylhexyl) phthalate (DEHP), the most commonly used plasticizer, were examined during accelerated thermal ageing in various environments. Weight loss was used to quantify loss of plasticizer. Attenuated Total Reflection Fourier Transform Infrared spectroscopy was used to quantify concentration of DEHP at surfaces of PVC. Distribution of DEHP was mapped using Low Vacuum Scanning Electron Microscopy. Optical densitometry was used to quantify darkening of samples.

Degradation of new and deteriorated PVC was inhibited by enclosure in a non-adsorbent material such as glass, containing still air. Such storage minimized migration and loss of DEHP.