漂白化学针叶木泡沫浆料流变性能的研究

Study on Rheological Properties of Bleached Chemical Softwood Foam-fiber Suspension

中文关键词:  泡沫浆料  聚乙烯醇  表观黏度  黏滞系数  流动指数

Key Words:foam-fiber suspension  polyvinyl alcohol  apparent viscosity  viscosity coefficient  flow index

中文摘要:

      采用桨式转子流变仪测量并分析研究了漂白化学针叶木泡沫浆料的流变曲线及流变参数变化规律。结果表明，未起泡时，加入聚乙烯醇（PVA）的针叶木浆料为Herschel-Bulkley塑性稀化流体，其表观黏度大于普通浆料。起泡后，针叶木浆料流变曲线分为剪切变稀阶段和剪切增稠阶段。纤维质量浓度为1.5%、2.0%和2.5%时，针叶木泡沫浆料流变性能转折点对应的剪切速率分别约为120、150和190 s^-1。PVA质量浓度对针叶木泡沫浆料的流变性能影响较小。针叶木泡沫浆料的质量浓度越高，其剪切应力和表观黏度越大。随着针叶木泡沫浆料含气率的提高，其剪切变稀阶段的黏滞系数K₁呈线性递增，剪切增稠阶段的黏滞系数K₂呈幂函数递减；而剪切变稀阶段的流动指数n1呈线性降低，剪切增稠阶段的n2与之变化规律相反。

Abstract:

      The rheological curves and rheological parameters of bleached chemical softwood foam-fiber suspension were measured by the rheo-meter with a propeller-type rotor. The results showed that the fiber suspension with polyvinyl alcohol （PVA） was Herschel-Bulkley plastic shear-thinning fluid when it was not foamed， but its apparent viscosity was higher than that of general fiber suspension. The rheological curves indicated two-stage rheological behavior of the foam-fiber suspension with PVA， shear thinning stage and shear thickening stage. The corresponding shear rate of each rheological turning points between the two stages were about 120， 150， and 190 s^-1， respectively when the fiber mass concentration was 1.5%， 2.0%， and 2.5%. The PVA content had little effect on the rheological property of foam-fiber suspension. The foam-fiber suspension with higher fiber mass concentration had higher shear stress and apparent viscosity. Increasing air content increased the viscosity coefficient K₁ linearly in the shear thinning stage， but reduced viscosity coefficient K₂ followed power-law trend in the shear thickening stage； decreased the flow index n₁ linearly in the shear thinning stage， but increased low index n₂ linearly in the shear thicke-ning stage.