Avaliação das propriedades de compósitos de poli(hidroxibutirato-co-valerato) reforçado com fibras de curauá

Abstract

Composites are materials composed of two or more different materials, forming a heterogeneous class of materials which differ in physical and chemical properties. Recent studies on biodegradable polymer composites reinforced with natural fibers show that these materials, in addition to totally biodegradable, present thermal and mechanical properties superior to those of conventional polymers. Poly(hydroxibutyrate-co-valerate) – PHBV - is a biodegradable polymer, inside the family of polyhydroxyalkanoates (PHAs) with mechanical properties similar to those of polypropylene. Curauá fibers have high strength when compared with other fibers such as jute, sisal and flax. This study aims to evaluate the incorporation of curauá fibers to the PHBV matrix, considering the influence of fiber content, the application of an alkaline pretreatment on the fibers, and the addition of a coupling agent (vinyl-trietoxi-silane). The composites were obtained by extrusion and injection and were evaluated its thermal properties, mechanical, morphological and biodegradation beyond the identification of functional groups. The results demonstrate that PHBV composites reinforced with 20% m / m of curauá fiber have properties superior to those of pure polymer. The alkaline pretreatment removed lignin and hemicellulose fibers, which promoted an increase in its apparent roughness, increasing the adhesion of the fiber to the matrix. The composites with fibers treated with alkaline solution with a concentration of 5% NaOH showed better mechanical properties. The vinyl-trietoxi-silane - VTES - applied on the fibers stimulated a better adhesion between the fibers and the matrix, and the composite with 2% VTES showed increased mechanical and thermal properties. The combination of the alkaline pretreatment and the coupling agent led to an increase in thermal and mechanical properties of the composites. The test of exposure to simulated soil showed that the curauá fibers colaborated in the composite biodegradation process. It was concluded that PHBV composites with curauá fibers treated with NaOH solution and using VTES exhibit thermal, mechanical and degradation superior to the pure polymer, and thus, can be used as an engineering material.