PVC/MMT nanocomposites

Abstract

Poly(vinyl chloride) (PVC) nanocomposites with sodium montmorillonite (Na-MMT) and organically modified MMT (O-MMT) have been prepared by melt processing using mixing and extrusion techniques. The differential scanning calorimetry (DSC) with stochastic temperature modulation (TOPEM™) results show that the glass transition temperature (T g) of PVC is slightly higher than T g of PVC/Na-MMT and PVC/O-MMT which would indicate that MMT plays a role of an internal plasticizer that increases the distance between the PVC macrochains. The DSC TOPEM non-reversing heat flow profiles show enthalpy relaxation effects, and the lowest value has been found for pristine PVC—the presence of MMT (both Na+ and ammonium salt modified) may generate a certain orientation level of PVC macrochains during the extrusion process. Specific heat vs temperature dependencies at different frequencies revealed that the best fit to the single profile was found for PVC/Na-MMT nanocomposite, and this observation may be related to internal stability of the composite material as confirmed by analysis of the change in the specific heat (Δc p).