Advanced polypropylene random copolymer nanocomposites: Effect of natural bentonite clay and aluminum hydroxide on morphology and properties Scientific paper

Abstract

This paper examines the influence of nanoparticles of the natural mineral bentonite and aluminum hydroxide in obtaining nanocomposites that are based on a compatibilized polypropylene random copolymer. A random copoly­mer of ethylene and propylene modified with maleic anhydride was used as a compatibilizer. The total amount of filler introduced into the polypropylene ran­dom copolymer composition was 50 wt. %. To study the synergistic effect, using a mixture of fillers, bentonite was included in the formulation at five different concentrations (5, 10, 15, 20 and 25 wt. %). The composites were obtained by mechanical mixing in the melt of a compatibilized polymer matrix. The struc­tural, morphological, physical-mechanical, thermal properties and fire resistance of the obtained composite materials were determined. The structural and mor­phological properties were characterized using infrared spectroscopy (IR) and scanning electron microscopy. Based on the results of IR and scanning electron microscopy-energy dispersive X-ray spectra, the presence of elements and bonds corresponding to the composition of bentonite and aluminum hydroxide, which were used as fillers in the composition of the polypropylene random copolymer, was confirmed. Morphological study revealed minor agglomerates of bentonite nanoparticles. Thermal properties of the obtained composites were determined using therm­ogravimetric analysis and differential scanning calorimetry. Ther­mogravimetric analysis showed that the addition of bentonite increases the ther­mal stability of composites, as evidenced by a decrease in the rate of mass loss. Mechanical properties (tensile strength, elongation at break) decrease with inc­reasing bentonite concentration. The synergistic effect obtained by the combined use of aluminum hydroxide and bentonite was manifested mainly in an increase in the melt flow index of the composite. The sample containing 25 wt. % natural bentonite showed the highest melt flow index values, up to 3.12 g/10 min.