Physical, Chemical, Soda Pulping and Papermaking Properties of Kenaf as a Function of Growth, 1998 Pulping Conference Proceedings

Kenaf (Hibiscus canabinus) is a most promising non-wood plant fibre source for pulping and papermaking. Because the plant composition (chemical and physiological) changes with the developmental stage of the plant, research is needed to determine its pulping properties at various stages of growth in order to establish the optimum harvesting time. Chemical composition and pulping properties of kenaf as a function of growth have been studied. Kenaf plants were harvested at the end of 90, 120, 150 days and one at maturity (200 days). The extractive-free samples were cooked at three different temperatures of 140
C, 155
C, and 170
C with soda cooking liquor of 32 g/L NaOH with active alkali charge of 15% as Na2O and liquor to wood ratio of 6:1. The chemical analyses show that the differences in holocellulose, alpha-cellulose, hemicellulose, and lignin content for 3, 4, 5 month old kenaf are not significant, except for mature kenaf. Mature kenaf has higher lignin and lower holocellulose content. Higher lignin content indicates the need for high consumption of chemicals for pulping and bleaching. Lower holocellulose content on the other hand gives lower pulp yield and strength properties. The Duncan’s test indicates that the differences in the mean values of soda pulping of kenaf at various stages of growth are not significant. In comparing the yields of kenaf pulps, it is observed that the average yield for 5-month-old kenaf over the whole range of cooking times and temperatures studied is the highest (60.4 %), amongst the group compared. Based on the results of chemical analyses of this study kenaf can be harvested at the end of 5 month growth period to achieve optimum pulp and paper properties.