Morphology, thermal and mechanical properties of PVC/MMT nanocomposites prepared by solution blending and solution blending + melt compounding

Two types of montmorillonite (MMT), natural sodium montmorillonite (Na-MMT) and organically modified montmorillonite (OMMT), in different amounts of 1, 2, 5, 10 and 25 phr (parts per hundred resin), were dispersed in rigid poly (vinyl chloride) by two different methods: solution blending and solution blending + melt compounding. The effects on morphology, thermal and mechanical properties of the PVC/MMT nanocomposites were studied by varying the amount of Na-MMT and OMMT in both methods. SEM and XRD analysis revealed that possible intercalated and exfoliated structures were obtained in all of the PVC/MMT nanocomposites. Thermogravimetric analysis revealed that PVC/Na-MMT nanocomposites have better thermal stability than PVC/OMMT nanocomposites and PVC. In general, PVC/MMT nanocomposites prepared by solution blending + melt compounding revealed improved thermal properties compared to PVC/MMT nanocomposites prepared by solution blending. Vicat tests revealed a significant decrease in Vicat softening temperature of PVC/MMT nanocomposites prepared by solution blending + melt compounding compared to unfilled PVC. The mechanical properties of the PVC/MMT nanocomposites were, in general, greatly improved compared to unfilled PVC. Nanocomposites with 2 phr and 5 phr of OMMT have demonstrated enhanced results in Young’s modulus, tensile strength and elongation. The Mori–Tanaka method along with an orientation distribution function was used to predict the effective stiffness of the PVC/OMMT nanocomposites prepared by solution blending + melt compounding method. Experimental values for 1 and 2 phr are larger than the calculated values which directly suggest that the MMT particles are exfoliated.