Effect of fiber fractionation on refinability and strength propertes of wheat straw soda-AQ pulp

Fereshteh Fadavi


Environmental and population growth pressures increased the interest in nonwood raw materials such as wheat straw for pulp and paper manufacture. Beating studies for straw based pulps showed that its freeness decreases faster than wood pulps. In other words wheat straw requires considerably lower energy or fewer PFI refiner revolutions than wood based furnish to reach the same level of freeness due to higher content of primary fines and thiner fibers at lower cell wall thickness. The effect of seperate refining of long fiber fraction on refinability and strength properties of wheat straw soda-AQ pulp are disscused in this paper. Thus soda-AQ pulp of wheat straw was fractionated using modified Buaer-Mc Nett fiber classifier having only a 50 mesh screen into a long fiber fraction (reject) and a short fiber fraction (accept) at two different mass split ratios of LFR 80 (80:20) and LFR 60 (60:40). The refined long fiber fractions were remixd with the related unrefined short fiber fraction and their properties were determined in comparison with the control sample. The air resistance, tensile and burst indices improved by the fractionation treatments especialy in the case of LFR 80, due to higher applied refining energy which lead to higher fiber to fiber bonding. By fractionation of wheat straw pulp and separate refining of longer fiber fraction it is possible to increase PFI revolution or refining energy to develop inter-fiber bonding strength without decreasing the tear index.

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