Fabrication and mechanical properties of unidirectional jute/PP composites using jute yarns by film stacking method

This paper mainly focuses on the fabrication process of long fibre reinforced unidirectional thermoplastic composites made using both natural ( untreated) and treated jute yarns. Jute yarns were wound in layers onto a metallic frame. Polypropylene films were inserted between these layers and compression moulded to fabricate unidirectional jute/ PP composite specimens. Static mechanical properties were evaluated from tensile and three point bending tests. Pre- and post-failure examination were carried out on the test specimens using optical and scanning electron microscopy to analyse the test results and investigate the correlations between their impregnation state, processing conditions, mechanical performances and fracture morphologies. For the unidirectional jute/ PP film-stacked composites, the results indicated that the processing condition at the moulding temperature of 160 degrees C and moulding pressure of 2.0 MPa for 15 min was ideally suited to obtain optimized properties. Improved wettability of resin melts due to complete matrix fusion at this processing condition facilitated thorough impregnation with minimum microstructural imperfections ( microvoids) being generated. Jute/ PP composites that contained treated jute yarns have shown superiority in tensile and bending properties. Jute yarns polished or coated with PVA/PP (polyvinyl alcohol/ polypropylene) must have contributed positively to fibre/matrix interfacial interactions leading to matrix to fibre effective stress transfer, and thereby improving their reinforcing effects. Tensile strength and modulus of PP resin increased by approximately 285% and 388%, respectively, due to 50wt% reinforcement by natural jute yarns. Further improvements in strength and modulus were achieved by approximately 14% and 10%, respectively, when treated yarns were used. The maximum bending stress and modulus of jute/ PP composites containing untreated yarns were approximately 190% and 460% higher than those of the virgin PP materials, and bending properties were improved by further 11% and 23%, respectively, due to coating treatments on the yarn surface.