Efeito da argila vermiculitas nas propriedades do biopolietileno de alta densidade.

Abstract

Polymeric composites reinforced with mineral fillers have aroused the interest of researchers because they present better thermal and mechanical properties when compared to pure polymers. Biopolyethylene / vermiculite biocomposites were prepared by extrusion followed by injection, in order to evaluate the effect of the natural clay and pyroexpanded content on the properties of these systems. Initially, the thermal treatment of piroexpansion, the beneficiation and characterization of the samples of natural vermiculite (NV) and piroexpanded (PV) were performed. BioPE/NV and BioPE/PV concentrates were prepared in 1: 1 ratios of BioPE and clay (NV or PV) in a Thermoscience Haake Polylab internal mixer. Concentrates obtained in the internal mixer were diluted in BioPE in a modular co-rotational twin screw extruder at concentrations of (0.5; 1; 3; 5 and 10) pcr clay and the specimens were injection molded in an Arburg Injector. Then, thermal, mechanical and rheological properties were analyzed, as well as microstructural aspects. It was observed that the addition of NV and PV clays to BioPE increased the Heat Deflection Temperature (HDT) and improved the fire retardance. In general, the degree of crystallinity (Xc) of BioPE decreased with the increase in the NV clay content, whereas in the presence of PV clay, the decrease in the Xc was only observed for the EV clay content above 3 phr. VP clay particles were better dispersed in the BioPE matrix, while many VN clay clusters were formed. The micrographs showed a lack of adhesion between the BioPE matrix and the NV or PV clay, resulting in a decrease of tensile and impact strength. Rheological measurements under oscillatory shear flow indicated the formation of a percolated network structure in the BioPE-NV and BioPE-PV biocomposites containing 5 and 10 phr of NV or PV clay. The biocomposite containing 10 phr of PV clay presented the higher melti yeld stress value. Rheological measurements at high shear rates showed that the processability of the biocomposites will be similar to that of neat BioPE.