Formation of microfibrillar structure of polypropylene/copolyamide blends in the presence of nanoparticles of metal oxides

Abstract

The influence of nanoparticles made of ifferent metals oxides (ZnO, Al2O3, TiO2, and ZnO/Al2O3) on the in situ formation of microfibrils by the components of a dispersed phase was studied in a thermodynamically incompatible blend of polypropylene/copolyamide (PP/CPA). The viscosity of the melts was determined by capillary viscometry method. Elastic properties were evaluated by the degree of extrudate swelling. The morphology of the compositions was studied by optical polarization microscopy. The method of image analysis was used to quantify the structural characteristics of the blends. It was established that the introduction of 1.0 wt.% of nanoparticles of the studied oxides made from different metals allows tuning the microstructure of the melt of the PP/CPA blend, which is realized in the course of extrusion. More perfect morphology is formed in nanofilled systems: the average diameter of PP microfibrils decreases and their mass fraction increases. The modifying effect of oxide nanoparticles is manifested due to their influence on interfacial phenomena and rheological properties of nanofilled PP melt. The viscosity of the PP melts increases and their elasticity decreases in the presence of nanoparticles of the studied metal oxides. The values of the ratio of the viscoelastic characteristics of the dispersed phase and the matrix in nanofilled systems depend on the nature of oxide and indirectly correlate with the microstructure of the extrudate. As these ratios approach unity, the diameter of PP microfibrils decreases and their share increases. The efficiency of the studied oxides to improve the microfibrillar structure increases in the following series: ZnO, Al2O3, TiO2, ZnO/Al2O3. The obtained results demonstrate the possibility to create the microfiber textile and filter materials with improved consumer characteristics by adjusting the phase morphology of the blends.