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Biocomposites of polymers with vegetal fibers have a broad spectrum of applications due to their high specific properties in comparison to their counterparts made with fiberglass. Polypropylene, PP, composites with curaua fiber compatibilized with different concentrations of maleic anhydride grafted polypropylene, PP-g-MA, were characterized according to their mechanical properties, morphologies and thermal stabilities in oxidative and inert atmospheres. The composites were prepared by single screw extrusion and injection molded specimens were used for testing. The composite with 20 wt % of curaua fiber with and without compatibilizer presented improved mechanical properties compared to pure PP. The use of PP-g-MA as a compatibilizer significantly increased fiber/matrix adhesion, however, the mechanical properties were only slightly improved in comparison with composites without compatibilizer. We observed an improvement in thermal stability of the composites, compared to that expected from the weighted average of the individual components, both under inert and oxidative atmospheres. Furthermore, the thermal stability improved under inert atmosphere as a function of the concentration of compatibilizer. In this situation, indeed, there was a different shift of the weight loss processes owing to the presence of the compatibilizer.

Summary Polyethylene and polypropylene are vastly employed for packaging due to their high versatility and low cost. However, their films are permeable at different degree to small molecules like gases and the use of additives improves the barrier properties. Therefore, the aim of this work is to investigate the effect of organically modified montmorillonite on oxygen transport properties of PE and PP films. Nanocomposites were prepared by means of polymer dissolution in organic solvent and subsequent nanoparticle addition at 3, 5 and 10% (w/w). Scanning electron microscopy images of the films indicate the presence of microcavities and some agglomerated nanoclay. On the other hand, X‐rays diffraction analysis shows clay in well‐dispersed state independent of polyolefin type. Enhancement of oxygen barrier is achieved, but this property is dependent on the nanoclay content, polyolefin type and film morphology.

Dedico essa dissertação aos meus pais, Maria e Ivail, pelo amor e apoio incondicionais, e ao meu namorado, Guilherme, pela paciência e amor que tornaram possível essa realização. vi vii Agradecimentos A Deus, pela vida. Aos meus pais, Ivail e Maria, por acreditarem que eu poderia alcançar meus objetivos e proporcionarem a base física e psicológica para tanto. Vocês são meu porto seguro.As minhas irmãs, Anna Clara e Lívia, pela presença, carinho e torcida.Ao meu amor, Guilherme, pelo carinho, paciência, vibração com as minhas conquistas e apoio em cada momento difícil que me ajudou a atravessar, enfim, por fazer parte da minha vida de uma forma tão importante.A minha família (avós, tios e primos) pela descontração e por compreenderem os momentos de ausência.Ao meu "tio Valdir", pela inspiração que me levou a tornar Bacharel em Química.Ao Prof. Marco-Aurélio, pela confiança, orientação e por ter me apresentado ao "mundo polimérico" e me transformado em uma "garota de fibra".A Joyce, pela convivência no laboratório e nas viagens e pelas discussões científicas que enriqueceram esse trabalho.A Márcia, por me acompanhar de perto nos primeiros passos na pesquisa.A Lea, Fillipe e Thais, pela bem-humorada convivência diária e pela ajuda nos momentos em que não estive presente no laboratório.