Tensile properties of short sisal fiber‐reinforced polyethylene composites

Abstract

SYNOPSISSisal fibers ( Agave-Veracruz) have been used as reinforcements in low-density polyethylene (LDPE). The influence of the processing method and the effect of fiber content, fiber length, and orientation on tensile properties of the composites have been evaluated. The fiber damage that normally occurs during blending of fiber and polyethylene by the meltmixing method is avoided by adopting a solution-mixing procedure. The tensile properties of the composites thus prepared show a gradual increase with fiber content. The properties also increased with fiber length, to a maximum at a fiber length of about 6 mm. Unidirectional alignment of the short fibers achieved by an extrusion process enhanced the tensile strength and modulus of the composites along the axis of fiber alignment by more than twofold compared to randomly oriented fiber composites. 0 1993 John Wiley & Sons, Inc. INTRODUCTIONSeveral cellulosic products and wastes such as shell flour, wood flour, and pulp have been used as fillers in thermoplastics primarily to achieve cost savings.' Over the past decade, cellulosic fillers of fibrous nature have been of greater interest as they would give composites with improved mechanical properties compared to those containing nonfibrous filler^.^-^ Lignocellulosic fibers like jute, sisal, coir, and pineapple have been used as reinforcements in thermoset mat rice^.^-^ Among these fibers, sisal is of particular interest in that its composites have highimpact strength besides having moderate tensile and flexural properties compared to other lignocellulosic fibers.lo3" A preliminary investigation has shown that sisal fiber can also be used as a reinforcement in a thermoplastic matrix and that it performs better than do wood fibers.12The mechanical properties of a short-fiber-reinforced polymer composite depend on many factors like fiber-matrix adhesion, volume fraction of fiber, * To whom correspondence should be addressed. Fiber aspect ratio should be above a critical value for maximum effect of reinforcement by attaining maximum stress in the fiber before failure of the composite. Fiber orientation has a significant influence on the mechanical properties of the composite in that the stress value is maximum along the axis of the orientation of the fiber. In addition to the above, factors like processing conditions /techniques also have significant influence on the mechanical properties of fiber-reinforced composites, particularly thermoplastic composites wherein fiber breakage during processing is a commonly observed phenomena.13 Therefore, a detailed investigation has been carried out on sisal-polyethylene composites, especially on the effect of fiber length, fiber orientation, and processing conditions on the tensile properties of the composites. The results are reported here. EXPERIMENTAL MaterialsPolyethylene ( LDPE-Indothene 16MA400) was supplied by Indian Petrochemicals Corp. ( Agave-Veracruz) was obtained from local sources.The fiber was washed with water and dried in an air oven at 80°C for 4-6 h befo...

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