Influence of plasticizer molecular weight on plasticizer retention in PVC geomembranes

Plasticizers are used to make PVC flexible so it can be used as a geomembrane. Plasticizers can migrate from PVC geomembranes over time because of contact with air, liquid, and/or an absorbent solid material. Plasticizer migration can reduce the flexibility of PVC geomembranes, resulting in brittle behavior. This paper discusses the three mechanisms of plasticizer migration and the factors influencing these mechanisms, such as plasticizer molecular weight and linearity of the plasticizer. Field case histories are used to show how these mechanisms influence plasticizer retention in PVC geomembranes. Finally, it is recommended that a minimum average plasticizer molecular weight of 400 be used to ensure long-term plasticizer retention and adequate field performance of PVC geomembranes. The weighted-average method for calculating the average molecular weight is recommended when two or more plasticizers are used in the PVC geomembrane formulation.