Density and Cell Morphology of Rigid Foam PVC-Clay Nanocomposites

Rigid PVC foam is becoming increasingly popular in the building materials industry due to recent advances in compound formulations and extrusion technologies. Amongst the most critical physical properties of rigid foams is the foam density. It not only determines the weight of the foam product, but it also controls its mechanical strength, stiffness, dimensional stability, and more importantly its cost. Foam density is usually maintained, through compound formulations and processing conditions, within a narrow range to ensure adequate product performance at a minimum material cost. The objective of this work is to investigate the effect of using different types of nanoclay fillers on the density and cell morphology of rigid PVC foam. Four different types of commercially available nanoclays were used: Natural Calcium Montmorillonite (unmodified), Sodium Montmorillonite modified with a quaternary ammonium salt, Aluminium Magnesium Silicate clay, and Magnesium Lithium Silicate clay. The individual and combined effect of nanoclay concentration and blowing agent content in the polymer melt on the foam density are reported. Optical Microscopy, SEM, XRD, and TEM imaging were used in the analysis of foam cell morphology and the dispersion and exfoliation of nanoclays in the polymer matrix.