Obtenção e caracterização do compósito PLA/argila refratária com propriedades de retardância de chama

Abstract

A biopolymer with good mechanical strength, biodegradability and good recyclability when compared to polymers commercialized nowadays, poly (lactic acid) (PLA) has attracted great attention from the academic community and the industrial sector due to its promising properties; however, it still has limitations regarding its flame retardancy properties. In this research, the effect of the incorporation, as reinforcement and flame retardant agent, of a refractory clay (RC) in a PLA matrix was investigated. The use of this clay was motivated due to its great abundance in the region of Poços de Caldas/MG, contributing not only in flammability improvements, but also in the final cost of the material. Composites were produced by melt compounding in an internal mixer varying the mass content of RC in 0, 2.5, 5, 7.5, 10, 15 and 20 wt% regarding the mass of PLA/AR. Neat PLA was also processed under the same conditions in order to act as reference. The composites that presented better mechanical performance (determined by statistical analysis ANOVA) were selected so, in a second set of experiments they were processed by extrusion and injection molding. According to ANOVA results, composites were produced with RC mass ratio of 0, 2.5, 10 and 15% in the mass of PLA/AR. TGA, DSC, FTIR, MEV, tensile, flexural and Izod impact tests were performed to characterize the polymer itself and the composites. Thermal analysis showed that the addition of different ratios of RC in the polymer matrix did not have a negative influence on the thermal stability of the material. The mechanical tests showed results of great relevance, since the RC did not go through surface modification in order to achieve better adhesion with the polymer matrix, and still the reductions in stress and strain were small (around 11%) when compared to neat PLA. There was a great reduction in the PLA flammability (according to UL 94 tests), since PLA/RC composites had faster self-extinguish properties than the reference material (neat PLA). The use of RC in this research brought an innovation in this field of study, with superior results from those found in the literature, considering that a greater incorporation of clay was possible, maintaining good mechanical properties, thermal stability and low flammability for the composites produced.