无机盐电解质对纳米纤维素流变性能的影响

Effects of Inorganic Salt Electrolytes on the Rheological Properties of Nanocellulose

关键词:  纤维素纳米纤丝  纤维素纳米晶体  流变性能  离子强度

Key Words:cellulose nanofibril  cellulose nanocrystal  rheological properties  ionic strength

摘要:本课题研究了不同阴阳离子的无机盐电解质对纳米纤维素悬浮液流变性能的影响。结果表明，纤维素纳米纤丝（CNF）和纤维素纳米晶体（CNC）悬浮液具有“剪切稀化”行为，剪切速率由0.01 s^-1增加到1000 s^-1时，悬浮液黏度从1000 Pa·s持续降至0.1 Pa·s。纳米纤维素悬浮液中添加不同价态的金属盐NaCl、MgCl₂、AlCl₃、Na₂CO₃和Na₃PO₄，随着金属盐添加量从0.001 mol/L增加到0.5 mol/L，纳米纤维素表面的双电层被破坏，静电排斥力减弱，使纳米纤维素颗粒沉积聚集，纳米纤维素悬浮液出现凝胶化现象。此外，随着阳离子强度的增加凝胶化越来越明显，悬浮液黏度增大，储能模量和损耗模量也随之增加。相反，受金属离子“静电排斥效应”的影响，随着阴离子强度的增加悬浮液黏度和模量变化不大，阴离子对纳米纤维素表面形成的双电层结构没有明显的破坏，无法明显降低纳米纤维素之间的作用。因而，阴离子强度的增加对纳米纤维素悬浮液凝胶化作用不明显。

Abstract:In this study， the effect of inorganic salt electrolytes of different anions and cations on the rheological properties of nanocellulose suspension was explored. The results showed that the suspension of cellulose nanofibril （CNF） and cellulose nanocrystal （CNC） had a “shear thinning” behavior. When the shear rate increased from 0.01 s^-1 to 1000 s^-1， the viscosity of the suspension decreased continuously from 1000 Pa·s to 0.1 Pa·s. When different valence metal salts NaCl， MgCl₂， AlCl₃， Na₂CO₃ and Na₃PO₄ were added to the nanocellulose suspension， with the increase of metal salt content from 0.001 mol/L to 0.5 mol/L， the double electrical layer on the nanocellulose surface was destroyed and the electrostatic repulsion force was weakened. Thus， the nanocellulose particles were deposited and aggregated， and the nanocellulose suspension was gelled. In addition， as the cation strength increased， the gelation became more and more obvious. Correspondingly， the viscosity of the suspension increased， and the storage modulus and loss modulus also increased. In contrast， influenced by the “electrostatic repulsion effect” of metal ions， the viscosity and modulus of suspension at the increase of anionic strength had little change， the anions had no obvious damage to the double layer on the surface of the nanocellulose， so the interaction between nanocellulose could not be significantly reduced. Therefore， the increase of anionic strength had little effect on the gelation of nanocellulose suspension.