通过在铜版纸面涂涂料中增加羧甲基纤维素用量来改善涂料流变性和保水性,对涂料的稳态剪切流变行为进行了研究.结果表明,随着剪切速率的增加,涂料表现出剪切稀化,呈现假塑性流体特性；另外,在同一剪切速率下,增加羧甲基纤维素加入量,涂料的表观粘度变大.采用两参数的 Bingham,三参数的 Herschel-Bulkley 及四参数的 Carreau 方程对涂料的流变曲线进行了数学拟合.结果表明,Carreau 方程能够准确地描述涂料的流变曲线,Herschel-Bulkley方程次之,而Bingham方程拟合效果较差.根据 Car-reau方程拟合结果,羧甲基纤维素加入量为0．5％,0．8％和1．0％时,涂料的零剪切粘度分别为100．8,155．7,161．8 Pa·s,极限粘度相应为0．03170,0．03934和0．05764 Pa·s,这说明羧甲基纤维素对铜版纸涂料具有明显的增稠作用.另外,涂料流动特性指数均小于1．0,呈现明显的假塑性流体特性,这与剪切稀化的实验流变结果吻合.%Carboxymethyl cellulose (CMC)holds great promise for modifying the rheological behavior and im-proving the water-holding capacity of paper coatings.In the present work,the influence of CMC addition on the rheologcial behavior of paper coatings was studied,and the rheological curves were fitted by using various rheo-logical models,e.g.,Bingham,Herschel-Bulkley,and Carreau model.It was indicated that all paper coating samples exhibited decreases in viscosity with the increased shear rate from 0 to 2 000 s-1 ,characterized as pseu-doplastic fluids.On another aspect,at the same shear rates,the viscosity of paper coatings increased signifi-cantly as the CMC addition increased from 0.5 to 1.0%.The rheological curve fitting results confirmed that Car-reau model may be the best one to well describe the rheological curves of paper coatings in comparison to Bing-ham and Herschel-Bulkley models.Particularly,the obtained rheological parameters including zero-rate viscosi-ty,infinite-rate viscosity and shear rate index derived from Carreau model provided opportunities to ascertain the changes in pseudoplastic behavior.As a result of Carreau model fitting,when increasing the added CMC a-mount from 0.5% to 1.0%,zero-rate viscosity of paper coatings increased from 100.8 to 161.8 Pa·s,and infi-nite-rate viscosity changed from 0.03170 to 0.05764,respectively,supporting the role of CMC in viscosity-in-creasing of paper coatings.Moreover,shear rate index of paper coating were all less than 1.0,showing the flow behavior of shear thinning,which may be consistent with the rheological curves.
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