Chemical Characterisation And The Effect Of Alkaline Pulping Of Malaysia Cultivated Kenaf (Hibiscus cannabinus)

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Date
2010-03
Authors
Ang, Lin Suan
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Publisher
Universiti Sains Malaysia
Abstract
A comprehensive study is carried out on the chemical composition of the bast and core of the Hibiscus cannabinus (kenaf) cultivated in Malaysia. The changes in the whole stalk chemical composition due to different plant age are also examined. In comparison to the kenaf planted in Malaysia and different countries, the locally planted kenaf (Penang) shows some differences in the value of the chemical composition. Increase of plant age from 15 to 19 weeks of kenaf growth are positively decreases the extractive content, but negatively increases the lignin content and decreases the holocellulose content. Based on the results of various soda-AQ pulping, it is found that the carbohydrate degradation and delignification degree increases with the increase of active alkali and cooking temperature, but the degree decreases with the increase of liquor to material (L: M) ratio. The most satisfactory properties of pulp and handsheets from kenaf bast can be attained by employing 19.4% active alkali with 0.1% AQ and L: M ratio of 7:1 cooked for 2 hours at 160°C. Besides, mild alkaline pre-impregnation prior soda-AQ pulping does not only effectively improve the pulp viscosity, but it also substantially increased the handsheets’ strength properties, especially folding endurance, tensile and burst indices. Among the three alkaline cooking processes (kraft, kraft-AQ and soda-AQ), the results of pulp and handsheet properties shows that the soda-AQ pulp is comparable or even slightly of higher quality than the kraft and kraft-AQ pulps. The study also found that between the kenaf bast and core soda-AQ handsheets, the strength properties of the kenaf core’s handsheet are surprisingly higher than of the kenaf bast. Nevertheless, the kenaf core shows considerable lower screened yield than kenaf bast. On the other hand, the effect of four chemical variables (NaOH, H2O2, stabilizer (NaSIO3 + MgSO4) and DTPA) of the kenaf core alkaline peroxide mechanical pulping and their interactions on the five responses—pulping yield, ISO brightness, tensile, tear and bursting indices are statistically evaluated by employing a two-level full factorial experimental design through a computer aided software named Design Expert®. The statistical analysis shows that the addition of stabilizer improve all the handsheets’ strength properties, while the increase of alkaline charge decrease the pulping yield and the increase of hydrogen peroxide charge increases the pulp brightness. All the factorial designs built are also statistically and experimentally verified.
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The chemical composition of the bast and core , of the Hibiscus cannabinus cultivated in Malaysia
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