Avaliação das propriedades mecânicas, térmicas, morfológicas e degradação de compósitos de poli(ácido lático) / buriti

Abstract

Nowadays, preoccupation with the environment has stimulated the use of biodegradable polymers substituting the synthetic ones, which are harder to degrade under different conditions. However, the properties of the biodegradable polymers can be improved by using fibers as reinforcement, in the form of composites and the interaction of matrix/fiber can be improved using agents of coupling. Studies about composites that use biodegradable polymers and natural fibers has attracted the academic and technological interest showing desirable characteristics for some applications and, post use, they biodegrade. As a challenge, the present study offers the development and the mechanical, thermic and morphological characterization of composites using the poly(lactic acid) (PLA), buriti fiber and triacetin as coupling agents. For the composites development, the buriti fibers were grounded and cut in sizes of 2,5; 5,0 and 7,5 cm mass with the use of 20% fiber mass, being after tested in concentration of 10 and 30 % mass. The triacetin was valued in the composites with concentrations of 10 and 30% mass. The composites were processed in two extruders, single and double screw. The specimens were produced by injection and compression. The results of this study were valued by the mechanic properties for tensile and flexural strength, morphological by scanning electron microscopy (SEM), thermal by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and chemical by Fourier transform infrared spectroscopy (FTIR). The fine content between condition and concentration of good fiber and the agent fiber was tested in two different environments, simulated soil and marine simulated soil, with the purpose of evaluating the biological degradation of the developments. In relation to the different lengths of buriti fiber tested, it was not observed differences in the mechanical and thermal properties, being the final fiber properties and dimensions similar to the results of the ground fiber. The mechanical properties of the composites with 30% of buriti fiber, appeared similar to those of the PLA virgin, these results were assigned to the fiber content and the interaction obtained between the matrix fiber using 5% in triacetin mass, the largest percentage tested. Related to the thermal properties, it was observed that the presence of buriti fiber decreases the thermal stability of the composites, but it increases the crystallinit. The exposition of the composite with 30% buriti fiber and 5% of triacetin showed different behavior in the two environment degradation it was tested. The proposed degradation environments made physical, chemical, thermal and morphological modifications in the composites, enabling to conclude that after the analysis of the results of the crystallinit , index of carbonila, residual mass and morphology, for 60 days of exposition, the buriti fiber and the triacetin improved the PLA biological degradation, making its hydrolysis in less time than the PLA virgin, being the hydrolysis more accented in the simulated marine environment, in the compositions, dimensions and specific means of this study. At last, we come to the conclusion that the use of composites of biodegradable polymers with natural fibers, in this study PLA/ buriti, substituting inert to degradation polymers is technically and environmental viable.