Influência do tratamento físico da fibra de coco nas propriedades mecânicas do biocompósito com matriz de poliéster insaturada
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Data
2018-07-30
Autores
Oliveira, Daniel Magalhães de
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Universidade Estadual Paulista (Unesp)
Resumo
Maior conscientização em relação as questões ambientais, atrelada a escassez de recursos, problemas ambientais globais e a políticas ambientais cada vez mais fortes influenciaram indústrias e pesquisadores a apreciar, estudar e desenvolver novos materiais a partir de fontes renováveis e novas tecnologias de fabricação. Entretanto, na literatura é reportado que a adesão interfacial entre fibras naturais e matriz polimérica é um fator que afeta as propriedades mecânicas do biocompósito, podendo ser melhorada por diversos tipos de tratamentos superficiais. Assim sendo, mantas de fibra de coco foram tratadas superficialmente por jato de plasma atmosférico, considerado menos agressivo ao meio ambiente quando comparado a tratamentos químicos, com o intuito de melhorar a adesão interfacial do biocompósitos. As fibras de coco foram caracterizadas com o objetivo de verificar a influência do tratamento nas propriedades físicas, químicas e térmicas. Verificou-se que o tratamento modificou a superfície das fibras e, consequentemente, sua hidrofilicidade e energia superficial, diminuindo o valor da permeabilidade. Parâmetros de processamento e o ciclo de cura mais adequado foram determinados como 80 ºC por 210 min, 135 ºC por 180 min e 160 ºC por 120 min, sem a aplicação de vácuo durante o processo e com fração volumétrica de fibras de aproximadamente 40 %. Inspeção acústica por ultrassom permitiu avaliar o processamento das placas dos biocompósitos verificando possíveis imperfeições causadas pela impregnação da fibra pela resina e sua homogeneidade. As análises termogravimétricas indicaram que a temperatura inicial de degradação dos biocompósitos é de 175 ºC. A temperatura de transição vítrea, determinada por DMA, é de aproximadamente 80 ºC. Os ensaios mecânicos apresentaram maiores valores de resistência à tração e de resistência à flexão para os biocompósitos reforçados com fibras tratadas quando comparados aos biocompósitos reforçados com fibras in natura. Maiores valores do módulo em tração e módulo em flexão, bem como os módulos de perda e armazenamento calculados por DMA para os biocompósitos reforçados com fibras tratadas sustentaram melhores propriedades mecânicas como resultado do tratamento a plasma. A morfologia da fratura dos biocompósitos indicou uma melhor adesão reforço-matriz para os biocompósitos com fibras tratadas.
Greater awareness regarding environmental issues, coupled with scarcity of resources, global environmental problems, and increasingly strong environmental policies have influenced industries and researchers to appreciate, study and develop new materials from renewable resources and new manufacturing technologies. However, literature reports that interfacial adhesion between natural fibers and polymeric matrix is a factor that affects the biocomposite mechanical properties, able to be improved by several types of surface treatments. Thus, coconut fiber mats were surface treated by atmospheric plasma jet, considered less aggressive to the environment when compared to chemical treatments, in order to improve interfacial adhesion with the polymer matrix to obtain biocomposites. Data from coconut fiber characterization shown that the treatment modified the fibers surface and consequently their hydrophilicity and surface energy, decreasing their permeability value. Processing parameters and most appropriate curing cycle were determined and defined as 80 °C for 210 min, 135 °C for 180 min and 160 °C for 120 min, without application of vacuum during the process and approximately 40 % fiber volume fraction. Ultrasonic acoustic inspection allowed evaluating the biocomposite plates processing by verifying possible imperfections caused by impregnation of the coconut fiber by the resin and its homogeneity. Thermogravimetric analysis indicated that the initial biocomposite degradation temperature is 175 °C. Glass transition temperature, determined by DMA, is approximately 80 °C. Mechanical tests presented higher values of tensile strength and flexural strength for the biocomposites reinforced with treated fibers when compared to the biocomposites reinforced with untreated fibers. Higher values of tensile and flexural modulus, as well as DMA loss and storage modulus for biocomposites reinforced with treated fibers sustained better mechanical properties because of the plasma treatment. Fracture morphology indicated better reinforcement-matrix adhesion for biocomposite reinforced with treated fibers
Greater awareness regarding environmental issues, coupled with scarcity of resources, global environmental problems, and increasingly strong environmental policies have influenced industries and researchers to appreciate, study and develop new materials from renewable resources and new manufacturing technologies. However, literature reports that interfacial adhesion between natural fibers and polymeric matrix is a factor that affects the biocomposite mechanical properties, able to be improved by several types of surface treatments. Thus, coconut fiber mats were surface treated by atmospheric plasma jet, considered less aggressive to the environment when compared to chemical treatments, in order to improve interfacial adhesion with the polymer matrix to obtain biocomposites. Data from coconut fiber characterization shown that the treatment modified the fibers surface and consequently their hydrophilicity and surface energy, decreasing their permeability value. Processing parameters and most appropriate curing cycle were determined and defined as 80 °C for 210 min, 135 °C for 180 min and 160 °C for 120 min, without application of vacuum during the process and approximately 40 % fiber volume fraction. Ultrasonic acoustic inspection allowed evaluating the biocomposite plates processing by verifying possible imperfections caused by impregnation of the coconut fiber by the resin and its homogeneity. Thermogravimetric analysis indicated that the initial biocomposite degradation temperature is 175 °C. Glass transition temperature, determined by DMA, is approximately 80 °C. Mechanical tests presented higher values of tensile strength and flexural strength for the biocomposites reinforced with treated fibers when compared to the biocomposites reinforced with untreated fibers. Higher values of tensile and flexural modulus, as well as DMA loss and storage modulus for biocomposites reinforced with treated fibers sustained better mechanical properties because of the plasma treatment. Fracture morphology indicated better reinforcement-matrix adhesion for biocomposite reinforced with treated fibers
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Palavras-chave
Plasma, Fibra de coco, Poliéster, Biocompósito, RTM, Propriedades mecânicas, Coconut fiber, Polyester, Biocomposite, Mechanical properties, Jato de plasma, Materiais compostos