This study focuses on the use of waste cotton fiber from the textile industry to produce composites with unsaturated polyester and to evaluate the performance of glass (G) / cotton (C) fiber laminates, particularly their mechanical and dynamic mechanical properties. Distinct stacking sequences were studied but the overall fiber content was kept constant. In general, hybrid laminates exhibited intermediate mechanical properties compared to those of the pure laminates, and optimum performance was obtained when the glass fiber mats were placed on the surfaces of the composite. Furthermore, some hybrid laminates exhibited superior dynamic mechanical performance, even compared to the pure glass laminate. Lower tan delta peak height (related to better fiber-matrix interaction) values and higher Tg were reported for the [C/G/ G ¯]s and [G/C/ C ¯]s samples which, together with the [G/C/ G ¯]s sample, exhibited the best results for reinforcement effectiveness and loss modulus peak height. Therefore, it is found possible to partially replace the glass fiber by waste cotton fiber considering that the final product may be optimized for mechanical property, which requires glass fiber at the surface of the laminate, or for dynamic mechanical properties, that allows higher cotton fiber content.

O objetivo deste trabalho é utilizar fibras de algodão como material de reforço em materiais compósitos poliméricos utilizando o poliestireno como matriz e o poli(estireno-co-anidrido maleico) como agente compatibilizante. Os compósitos foram desenvolvidos em uma extrusora dupla-rosca co-rotacional, precedidos de uma pré-mistura em extrusora mono-rosca e moldados por injeção. Os compósitos foram avaliados mediante ensaios mecânicos, térmicos, termo dinâmico-mecânico e de morfologia dos compósitos produzidos. Os ensaios de flexão e tração mostram que a adição de 20% de fibra de algodão faz com que essas propriedades aumentem, sendo esse efeito intensificado em presença de compatibilizante. Observou-se aumento da resistência ao impacto com adição de carga; porém, os compósitos com compatibilizante apresentaram resultados inferiores. A HDT para os compósitos com 20% de fibra de algodão foi de aproximadamente 7 ºC. Por meio do TGA, observa-se que a adição de fibras de algodão desloca o início da perda de massa para temperaturas próximas a 200 ºC. Na análise de DMTA, observa-se que, com a adição da fibra de algodão, ocorre aumento na rigidez e no módulo de armazenamento. As micrografias mostram redução no pull-out das fibras, devido a uma maior adesão fibra/matriz, com a utilização do agente compatibilizante.

The aim of this work is to use cotton fibers as reinforcement in polymeric composites materials using polystyrene as matrix and poly(styrene-co-maleic anhydride) coupling agent. The composites were developed by first mixing in a single screw extruder and a co-rotation parallel twin screw extruder and injection molded. The composites were characterized by analysis mechanical, thermal, dynamic mechanical thermal and morphology. The results from the flexural and tensile strength demonstrate that the addition of 20% cotton fibers tends to increase in these properties; however there is increase when using a coupling agent. The impact resistance increased with the increase of load; however the results of the composites with coupling agent were lower than those without. The temperature of thermal deflection increased for all composites, but the increase for the composites with 20% cotton fiber was approximately 7 ºC. The results show that the addition of cotton fibers changes the initial temperature of wheight loss for the composites to temperatures close to 200 ºC. The DMTA analysis showed increasing in stiffness and the storage modulus with cotton addition. The micrographs showed a reduction in the pull-out fibers, due to a greater adhesion fiber / matrix with the use of compatibilizer.