一维粒子对聚乙烯醇水溶液流变行为的调控

Regulation of Rheological Behavior of Polyvinyl Alcohol Aqueous Solution by One-dimensional Particles

将一维粒子(碳纳米管,CNTs;碳纳米纤维,CF)加入聚乙烯醇(PVA)水溶液中,考察碳粒子表面含氧官能团含量(羟值)、长径比、温度及PVA本体溶液浓度等对复合体系流变行为的影响.结果显示,复合溶液的黏度(η)随CNTs用量(φCNTs)先增大后降低,然后继续增大,呈“N”形变化趋势,出现两个拐点(φ1和φ2).在φ1附近,CNTs主要起物理交联点作用,体系η增加;在φ2附近,CNTs对PVA分子间氢键作用破坏最为严重,体系η低于纯PVA溶液,表明不同羟值CNTs仅改变其用量即可使PVA水溶液增黏或降黏.随着羟值增大,CNTs与PVA大分子间相互作用加强,φ1和φ2减小,φ2对应的η下降,降黏效果显著.CNTs的加入使PVA水合数下降,羟值大的CNTs可与PVA上更多的羟基形成氢键作用,水合数更低.随着φCNTs增大,复合体系黏流活化能增大.CNTs对不同质量分数PVA水溶液的η具有类似的调控作用,但调控幅度有差异.相同羟值、不同长径比的CNTs对PVA水溶液的黏度调控均呈“N”形变化,长径比小的CNTs复合体系,φ1和φ2较大.长径比相近但直径较大的CF复合体系表现出更低的φ1和φ2.

In this paper,one-dimensional particles were added into polyvinyl alcohol(PVA)aqueous solution.The effects of oxygen-containing functional group content(hydroxyl value)on the surface of carbon particles,aspect ratio(L/D),temperature and PVA bulk solution concentration on the rheological behavior of the composite solution were investigated.The results show that carbon nanotubes(CNTs)and carbon nanofibers(CF)can regulate the rheological behavior of PVA aqueous solution by changing hydroxyl value and L/D.The viscosity(η)of the composite solutions first increases,then decreases,and then continues to increase with the amount of CNTs(φCNTs),showing an“N”shape change trend.There are two transition points,i.e.φ1 andφ2.CNTs mainly play a role of physical crosslinking point atφ1,and theηincreases;while CNTs destroy the intermolecular hydrogen bond interaction of PVA chains most seriously atφ2,leading to a lowerηthan that of pure PVA solution.With the increase of hydroxyl value,the interactions between CNTs and PVA chains are strengthened,giving rise to the decrease of bothφ1 andφ2.Furthermore,ηcorresponding toφ2 decreases.This indicates the viscosity reduction effect is strengthened by the high hydroxyl value of CNTs.With the addition of CNTs,the hydration number of the composite solution decreases,implying that more hydroxyl group of PVA chains form hydrogen bond interaction with CNTs.The CNTs composite solution with high hydroxyl value has lower hydration number than that with low hydroxyl value.The viscous activation energy of the composite solution increases withφCNTs.CNTs have similar regulatory effects onηof PVA solutions with different concentrations,but the regulatory range is different.The viscosity regulation of PVA aqueous solution by CNTs with the same hydroxyl value and different L/D also show an“N”shape curve,but short CNTs com⁃posite solution with small L/D have largeφ1 andφ2.While the composite solutions containing CF with similar L/D but larger diameter show lowerφ1 andφ2.