Avaliação da utilização de aditivos de fontes renováveis em compósitos de poli(ácido lático) e casca de noz-pecã

Abstract

Polymer based composites with natural fibers as reinforcement generally presents problems in processing and due to the low interaction between polymers and natural fibers, often composite can suffer a downgrade in its properties. To solve that problem, some additives can be used to improve composite processability, such as plasticizers and coupling agents. This work has the objective to evaluate monocarboxylic and dicarboxylic acid, namely hexanoic acid (C6), hexanedioic acid (CC6), octanoic acid (C8) and octanedioic acid (CC8), on the chemical, mechanical, thermal, morphologic and rheologic properties of poli (lactic acid) (PLA) with pecan nutshell composites. Composites were processed in a twin-screw extruder and samples were obtained through injection molding. All additives were capable of improving composites flexural properties, compared to composite with no additive, however C8 composite where the one with the most notable improvement in flexure also in tensile modes, reaching a 72% higher flexural strength. The dynamic mechanical analysis (DMA) revealed the composites with additive were the most heterogenous ones, due to its larger full width half maximum of tan ? peak. Composites with additive presented reduction in its glass transition temperature (Tg), demonstrating that the oils may have played a role as plasticizers. However, some oils such as C8, demonstrated an increase on degradation initial temperature, indicating that there was an improvement in matrix-fiber interactions, demonstrating that the oils had a coupling agent behavior as well. Composites with additive presented lower complex viscosity, even in low frequencies, so those compounds may facilitate composite processing. The natural oils used in this work demonstrated potential as additives for polymer composites with lignocellulosic fibers, acting as coupling agent or plasticizer. [resumo fornecido pelo autor]