INFLUENCE OF SURFACE LIGNIN CONCENTRATION ON FIBRE SURFACE CHARACTERISTICS AND TENSILE PROPERTIES OF OIL PALM FIBRE/UREA-FORMALDEHYDE RESIN COMPOSITE

Surface lignin plays an essential role in the surface characteristics of fibre and the interfacial behaviour of composites prepared with cellulosic fibres. The influence of surface lignin concentration on fibre surface characteristics and tensile properties of oil palm fibre/urea-formaldehyde resin composite was studied by Scanning Electron Microscope (SEM), tensile testing, and internal bonding strength measurements. Fibre surface lignin was removed by chlorine dioxide (Cl02) treatment. The results show that surface lignin concentration was 49.5% for the untreated fibre, and then decreased dramatically to 14.1% for the fibre treated with 1.0% Cl02. Thereafter, it decreased slowly to 9.6% and 7.6% for the fibres treated with 1.5% and 2.0% Cl02, respectively. While fibre/resin interaction was found to be poor for composites prepared with treated fibres, it decreased progressively with composites made with treated fibres due to reduction in surface lignin as revealed by the tensile properties and internal bonding strength of the composites. The SEM micrographs of the fibres reveal an increase in the surface roughness and specific surface area of fibres with reduction in surface lignin, which is believed to have promoted better fibre/resin interaction. These results indicate that the surface properties of single oil palm fibres can be tailored to improve the fibre/resin interface by chlorine dioxide treatment.