Produção e caracterização de painéis compósitos constituídos de resíduos lignocelulósicos e misturas de resinas epóxi sintética e de óleo vegetal residual epoxidado

Abstract

Since the last decade, scientists and developers in the fields of materials engineering have shown concern about sustainability and environmental protection issues. The option to develop lignocellulosic composite materials presents itself as an environmentally correct alternative for the manufacturing industries, enabling the development of new materials with special technical characteristics in order to optimize the physical-mechanical properties of these materials. In this context, this work presents a study on the development, production and characterization of new composite panels made of lignocellulosic residues from coffee husks and mixtures of synthetic epoxy resins and epoxidized residual vegetable oil. For this study, the research methodology adopted encompasses the literature review, survey, preparation, organization and data and experimental analysis. The hybrid composites were prepared from the combination of untreated and alkalized coffee husk particles, respectively, as reinforcements of the mixture of epoxy resin matrix (DGEBA) and epoxidized residual soybean oil (OSRE). For this study, the OSRE-DGEBA compound was prepared using the thermo-curing technique, and coffee husk particle contents of 30% (m/m) with a matrix composed of 50% epoxidized residual vegetable oil were studied. and 50% petroleum-based epoxy resin. The specific mass of the composites was in the range of 1,130 to 1,380 kg/m3, with the lowest value for the highest content of coffee husk particles. Fourier transformation infrared spectroscopy has been successfully used to monitor the epoxidation of vegetable oils and the subsequent curing of epoxy resins and particle boards. The thermal stability of the compost was dictated by its lignocellulosic content and significant mass losses occurred at temperatures above 300ºC, regardless of the content of coffee husk residue particles. The polymer matrix was characterized by thermogravimetry (TGA), Fourier transform infrared spectrometry (FTIR) and flow index (MFI) tests. Coffee husk fibers were characterized by scanning electron microscopy (SEM). The lignocellulosic composites were prepared using a metallic matrix (mold) where the specimens were shaped for the tensile, three-point bending and Izod impact tests, in addition, a statistical evaluation was performed by analysis of variance (ANOVA). The cross-sections of the samples submitted to mechanical tests were characterized in terms of morphology, microstructure and polymer matrix-organic filler interface. Thermal, physicochemical, hygroscopic and flammability properties were also characterized. It was revealed that the lignocellulosic composites showed positive indices for the modulus of elasticity in traction and bending, stiffness and reduced toughness under impact. It was observed that, for this study, the values of tensile strength with reinforcement of organic filler were lower than those of the polymer matrix. The results obtained and the characterization of the researched materials demonstrate that the process developed is a viable manufacturing technique for the new composite panels made up of lignocellulosic residues and mixtures of epoxy resins, which exhibited superior or similar mechanical properties to several materials used in other studies.