Analysis of Glass Transition Temperature Depression of Polyvinylchloride Using Nucleophilic Substitution

Polyvinyl chloride (PVC) is one of the most ubiquitous plastics used in our society. Plasticizers are typically added to PVC to increase its flexibility by lowering the glass transition temperature (). PVC plasticization is most commonly performed using external plasticizers, which are small molecules (e.g. phthalates) that physically mixed into the PVC. Leaching of external plasticizers from PVC can degrade the properties of PVC and is a potential health risk.

Internal plasticization of PVC involves altering the chemical structure of PVC to lower the T_g. A significant benefit of internal plasticization is that leaching is typically not observed with internally plasticized PVC. This project focused on internal plasticization of PVC by substituting thiols onto the PVC chain. The effect between the degree of substitution of different thiols on PVC and of modified PVC samples was analyzed. Three thiols were substituted onto the PVC chain: 1-dodecanethiol, 2-ethyl-hexyl-thiol and 1-adamantanethiol. The amount of thiol added was varied to create a variety of degrees of substitution (DS) of PVC. Thermal data was collected using a differential scanning calorimeter (DSC). The thermal data was sampled for modified with thiols at different degrees of substitution to effectively compare the between degrees of substitution for different thiols.