A Study on the Antiplasticization Mechanism of PVC by Infrared Dichroism

Abstract

Infrared dichroism of PVC films containing less than 5wt.% of plasticizers such as DMP, DOP, DOA and TCP were measured for the absorption bands at 603, 635, 690, 1426 and 1434cm-1 for PVC and for C=O stretching vibration for plasticizers.In the plot of plasticizer level vs. orientation function while the minimum value of the crystalline absorption bands was clearly observed in the orientation function at around 2wt.% of plasticizer level, no clear presence of minimum value was assured of the amorphous absorption bands. This was proposed as interpretable in terms of antiplasticization mechanism caused by small amount of plasticizers acting as pseudo-crosslinking agents in PVC. The dichroic data were utilized for the estimation of possible effects of hydrogen bonding and charge transfer force on the intermolecular force between plasticizers and PVC.It is concluded that the majority of contribution to this pseudo-crosslink is from the hydrogen bonding between PVC and carbonyl group in the plasticizer molecule, while the charge transfer force is not large enough to affect the orientation of the polymer chain.