Optimisation of nanocomposites based on polypropylene/polyethylene blends and organo-bentonite

The effect of the organophilisation of a Na-bentonite, through cationic exchange reaction with a commercial quaternary benzalkonium salt, on the morphology and mechanical behaviour of polypropylene (PP)/low density polyethylene (LDPE) blend matrices has been investigated employing a statistical experimental design. The results show that the tensile modulus and strength of the composites increase (up to 760 and 360%, respectively) as both PP percentage in the matrix and clay content in the composite increase. The properties are more dependent on matrix composition than on clay content. In all cases, the organo-bentonite gives rise to more resistant materials in comparison with the Na-bentonite. Increments of 50–35% in stiffness and strength, respectively, have been observed. The elongation at break mainly depends on matrix composition and a minimum is observed when phase inversion has taken place. The organophilized bentonite gives rise, in some formulations, to an increase in elongation up to 400%. Theoretical equations to predict the tensile behaviour of composites based on PP/LDPE blends with Na-bentonite and benzalkoniun chloride modified bentonite, inside the investigated limits, have been deduced. A morphological study has been carried out by means of scanning electron microscopy.