Comparison of water absorption in natural cellulosic fibres from wood and one-year crops in polypropylene composites and its influence on their mechanical properties

Environmentally beneficial composites can be made by replacing glass fibres with various types of cellulose fibres. Fibres from pine or eucalyptus wood and also one-year crops such as coir, sisal, etc. are all good candidates. The poor resistance towards water absorption is one of the drawbacks of natural fibres/polypropylene composites. New natural fibres/polypropylene composites were made and the water absorption in them was studied by immersion of the composites in water at three different temperatures, 23, 50 and 70 degreesC. The process of absorption of water was found to follow the kinetics and mechanisms described by Fick's theory. In addition, the diffusivity coefficient was dependent on the temperature as estimated by means of Arrhenius law. A decrease in tensile properties of the composites was demonstrated, showing a great loss in mechanical properties of the water-saturated samples compared to the dry samples. The morphology change was monitored by scanning electron microscopy studies of the samples before and after exposure to water and the devastating effect of water on the fibre structure was shown. (C) 2004 Elsevier Ltd. All rights reserved.