Kenaf fibres for pulping and papermaking

Kenaf, a non-wood fibrous species used for papermaking has two morphologically different portions in its stem: the bast or long fibre fraction and the core or short fibre fraction. The objective of this research is to provide an explanation for the observed differences in properties of paper made from the two kenaf fractions, in both chemical and morphological terms.;Micro-pulping experiments were carried out to study the delignification potential of bast, core, and whole kenaf fibres. The activation energies for the different fractions were calculated using the Arrhenius equation and were 68 kJ/mole, 91 kJ/mole, and 75 kJ/mole for bast, core, and whole fractions, respectively. M.K.Systems digester followed by PFI beating was used to obtain pulps with a range of residual lignin contents and freeness values for making handsheets. Multiple regression analysis was then used to analyse paper strength properties in terms of the morphological and chemical characteristics of the pulps. Separate models for bast and core were developed, as they have a wide variation in activation energies and delignification potential. Elasticity or the relative rate of change in each strength property, with respect to a change in morphological or chemical property was also calculated. This helped to elucidate the relative sensitivity of the independent variables affecting the models.;The micro-pulping experiments led to the conclusion that the bast fibres in kenaf are relatively easy to delignify during pulping, followed by the whole and the core kenaf fractions. Also, for optimal utilisation of kenaf as a raw material for papermaking, the bast and core fractions should be processed separately and then blended, as per requirement. The regression analysis for the strength properties suggested that a major portion of the variation in the strength properties (as high as 96% for burst in core fibres) is explained by the models. The models presented in this research can serve as initial exploratory tools for further research in non-woods in general and kenaf in particular. It is concluded that in general, morphological factors are more important than chemical factors during the development of paper strength properties in kenaf fibres.