十二烷基硫酸钠对聚乙烯醇亚浓水溶液流变行为的影响

表面活性剂会影响聚乙烯醇(PVA)分子间及分子内氢键形成,进而改变其水溶液的流变响应.本文在确定十二烷基硫酸钠(SDS)在PVA亚浓水溶液中的临界聚集浓度(CAC)和临界胶束浓度(CMCP)基础上,考察了SDS对PVA亚浓溶液(10 wt%)流变行为的影响.研究发现,不同浓度SDScsur对PVA水溶液稳态流变行为的影响差异较大:(1)当csur CMCP,随着csur增加,胶束起物理交联点作用,ηa增大,复合溶液的动态储能模量亦显著增大.加入SDS后,PVA体系内结合水的数目降低,但当csur> CMC后,结合水的数目几乎不变,黏流活化能也表现出相近的变化规律.与稀溶液相比,SDS对PVA亚浓溶液的降黏幅度较大.

Effect of Sodium Dodecyl Sulfate on the Rheological Behavior of Poly (vinyl alcohol) Aqueous Solution

Rheological behaviors of poly(vinyl alcohol)(PVA) aqueous solution are influenced remarkably by the intermolecular hydrogen bond interaction in the semi-dilute solution region. Owing to the hydrogen bond network, 10 wt% PVA aqueous solution exhibits a high viscosity which limits the development of its solution processing method to some extent. Sodium dodecyl sulfate(SDS), as a surfactant, can destroy the hydrogen bond interaction, thus playing a certain viscosity-reducing role. Based on measuring the critical aggregation concentration(CAC) and critical micelle concentration of SDS in 10 wt% PVA aqueous solution(CMCP), the steady and dynamic rheological behaviors of PVA-SDS aqueous solution were studied in detail. The concentrations of SDS(csur) can influence the rheological behavior of PVA aqueous solution in different ways at various regions. csur < CAC, the apparent viscosity(ηa) of the solution doesn’t change a lot as the csur changes. CAC < csur < CMCP, ηa decreases as the csur increases. Particularly, ηa reaches the minimum while csur = CMCP and a wider second platform is displayed in this area. csur > CMCP, SDS form micelles that act as physical crosslinking points, and the dynamic storage modulus(G′) of the composite solution also increases significantly. The changes in the hydrogen bond network of the PVA solution was indirectly characterized by the changes of the hydration number measured by Differential Scanning Calorimeter. After introducing SDS, the number of bound water(n) decreases due to the interaction between SDS and PVA. However, n almost keeps constant when csur >CMCP. The viscous activation energy also shows a similar change. When csur is much larger, the micelles formed by SDS in water are conducive to the formation of physical cross-linking network, which contribute more to the solution elasticity, leading to the increase of G′(greater than that of dynamic loss modulus). Compared with the dilute solution, SDS has a greater viscosity reduction effect on the PVA semi-dilute solution.