Desenvolvimento de um processo para incorporação de fios de juta em matriz termoplástica e caracterização dos compósitos.

Abstract

Vegetable fibers can and are used to reinforce polymer matrices with varying degrees of success. The interest in investigating the viability of incorporating these fibers into polymers is associated with their availability, lightweight, low cost, good set of mechanical properties and environmental concerns as these fibers come from renewable sources, are non toxic, non abrasive to processing equipment and degrade fairly easily. Thus, omposites reinforced with these fibers would be considered to be ecofriendly. The use of vegetable fibres as reinforcement in thermoset matrices is well established. In the lastdecades, thermoplastic/vegetable fiber composites are being intensively investigated. However, in general, thermoplastic composites are reinforced with short fibers as these matrices are commonly extruded and/or injection molded, which limits composite property enhancement. Thus, in order to obtain thermoplasticlvegetable fiber composites with better mechanical properties, we have developed a method to manufacture long, continuous, aligned thermoplastic composites. The process consists of aligning and winding fiber yams around a metal plate, sandwiching them with plastic films and compression molding. The plates can then be stacked in different arrangements and consolidated byhot compression. In this work the tensile, flexural and impact properties of PP and LOPE/jute yarn composites, manufactured by the method described, were determined. Two polypropylene (PP) and one polyethylene (LOPE) matrices with different molecular weights were used asthe matrix and two jute yearns (classified as 10/1 and 1012) were used as reinforcement and used In the manufacture of composites having different fiber contents and orientations. Our data shows that the method proposed is viable and that significant property enhancements were achieved. Tensile strength and modulus significantly increased with fiber incorporation and content, although for the latter, better properties were achieved for composites having 2 reinforcing layers. It is believed this behavior may be associated with fiber impregantion and/or interface quality. The same trend was observed for flexural modulus and strength. Composite impact strenghts were significantly smaller than those of the matrices which is thought to be due to the incorporation of relatively rigid fibers into very ductile matrices. In general, higher moduli (tensile and flexural) were achieved by composites reinforced with the thinner thread (10/1), while those reinforced with the thicker jute thread ended to display higher strenght (tensile, flexural and impact).