Effect of montmorillonite addition (modified and unmodified) on the structural, mechanical, thermal, and morphological properties of nanocomposites based poly (vinyl chloride)

Abstract

Poly (vinyl chloride)/ montmorillonite nanocomposites were prepared using a melt mixing technique. For this purpose, three montmorillonite samples (MMT) namely, raw montmorillonite (R-MMT), sodium montmorillonite (Na+-MMT) and organically modified montmorillonite (O-MMT) were used with different contents (0, 1, 3, 5, 7 and 9 phr) in the presence of dioctyl phthalate (DOP). X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Differential Scanning Calorimetry (DSC), and mechanical testing were used to investigate the physical properties of nanocomposites (PVC/MMT). The results of XRD show that macromolecule chains of PVC may be intercalated or exfoliated into the gallery of modified montmorillonite (Na+-MMT and O-MMT). Microcomposites structure is formed on the PVC/R-MMT nanocomposites when the unmodified montmorillonite (R-MMT) content is added from 1 to 9 phr. However, the glass transition temperature (Tg) of PVC/O-MMT nanocomposites is shifted slightly to lower temperatures. Furthermore, O-MMT plays the role of an internal plasticizer hence increases the distance between macromolecule chains of the polymer. Consequently, the degree of interactions between the chains decreases inducing a decrease in Tg. Synergy effect is also observed on the PVC/O-MMT nanocomposites with the increase in the amount of O-MMT. The morphological study by AFM shows a reduction in surface roughness under the effect of montmorillonite modified, and particularly with (1 phr) of O-MMT.