Isora Fibres and their Composites with Natural Rubber

Abstract

This paper reports the use of a natural fibre ‘isora’ as reinforcement for natural rubber. Isora is a bast fibre separated from the bark of the Helicteres isora plant by retting. The effect of different chemical treatments on the fibre properties and on the mechanical performance of short isora fibre reinforced natural rubber (NR) composites has been investigated. The surface modifications carried out in this work include mercerization, acetylation, benzoylation, and treatments with toluene di-isocyanate and a silane. The treated and untreated fibres were characterized by infrared spectroscopy. The spectra indicate a reduction in the lignin content and the introduction of non-polar functional groups on the surface of the fibres. The thermal stability of the untreated and treated fibres was studied by thermogravimetry, which indicated that it could be improved by appropriate chemical treatments. Scanning electron microscopy (SEM) studies were carried out to investigate the fibre surface morphology, fibre pull-out and fibre- rubber interface bonding. SEM gives strong evidence about the nature of the physical and micro structural changes that occurred on the fibre surface on chemical modification. Mechanical properties such as tensile modulus, tensile strength, tear strength etc were measured to investigate the performance of the composites. Many of the properties were superior when the composites contained treated fibres. The improvement in the properties also indicated that the bonding of the NR matrix to isora fibres could be improved by chemical treatment.