The use of composites in structural applications requires the study of specific properties to ensure that these materials are safe and an excellent option to replace some metals, for example. In the present study, vacuum assisted resin transfer molding (VARTM) was used prior to obtain carbon/epoxy non-crimp fabric composites. Dynamic mechanical analysis and creep - by using Findley and Burger's methods - tests were performed aiming to evaluate the viscoelastic properties of the composites, in three different temperatures (30, 60 and 90°C) and static stresses (2, 5 and 10 MPa). The viscoelastic properties were also discussed using Weibull parameters obtained from creep curves. In general, the deformation was temperature and stress dependent, which was corroborated by the viscoelastic parameters obtained from both models.

Neste trabalho foi realizado um estudo cinético da redução da massa molar do poli(3-hidroxibutirato-co-3-hidroxivalerato) (PHBHV) em três diferentes metodologias: hidrólise ácida com ácido clorídrico, transesterificação com hexilenoglicol ou etilenoglicol e redução na presença do borohidreto de sódio (NaBH4). Foram investigados os parâmetros de processo: tempo, temperatura, tipo e concentração de catalisadores. Os resultados de redução de massa molar foram analisados pelo modelo cinético de ordem n. A redução com NaBH4 foi mais eficiente do ponto de vista cinético, tendo em vista os parâmetros: constante de reação k e energia de ativação (Ea), uma vez que os valores observados foram significativamente maiores em comparação com os calculados para os demais métodos.

In this work a kinetic study was carried out of the molecular weight reduction of poly(3-hydroxybutirate-co-3-hydroxyvalerate) (PHBHV) in three different methodologies: acid hydrolysis using hydrochloric acid, transesterification with ethylene glycol or hexylene glycol and reduction in the presence of sodium borohydride (NaBH4). The following process parameters were investigated: time, temperature, type and concentration of catalysts. The results of molecular weight reduction were fitted with a n-order kinetic model. The kinetics analysis has shown that the NaBH4 reduction was the most efficient in terms of reaction rate in comparison with the other methods.