Zhang Xiaolong, Hu Hongjiu, Guo Manxia
Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072, China.
Phys Chem Chem Phys. 2015 Feb 7;17(5):3186-95. doi: 10.1039/c4cp04966g. Epub 2014 Dec 18.
Regarding the underlying special relaxation feature of a water-plasticized hydrophilic polymer during performance evolution with water content change, we report the water desorption kinetics and periodic creep responses of poly(vinyl alcohol) (PVA) films subsequent to rejuvenation by above-glass transition relative humidity (RH) annealing and following RH-jump at various rates. A Moisture Sorption Analyzer and a Dynamic Mechanical Analyzer are utilized to control RH and to capture data to probe the evolving relaxation towards equilibrium under two temperature-RH conditions. This result reveals an evident jump rate dependence of desorption kinetics and recoverable creep deformation. The different target RH yields the different change patterns of normalized water content and retardation time. PVA manifests a rapid relaxation stage with the special viscoelastic response before experience of usual physical aging. By analysis of the superposition principle and the relevant characteristic parameters, the relaxation of the hydrophilic polymer after water desorption through the glass transition is generalized as three successive phases.
关于水增塑的亲水性聚合物在随含水量变化的性能演变过程中潜在的特殊松弛特性，我们报告了通过高于玻璃化转变相对湿度（RH）退火恢复活力后以及在不同速率的RH跳跃之后，聚乙烯醇（PVA）薄膜的水脱附动力学和周期性蠕变响应。利用水分吸附分析仪和动态力学分析仪来控制RH并采集数据，以探究在两种温度-RH条件下朝着平衡状态演变的松弛过程。该结果揭示了脱附动力学和可恢复蠕变变形对跳跃速率的明显依赖性。不同的目标RH产生了归一化含水量和延迟时间的不同变化模式。PVA在经历通常的物理老化之前表现出具有特殊粘弹性响应的快速松弛阶段。通过对叠加原理和相关特征参数的分析，通过玻璃化转变进行水脱附后亲水性聚合物的松弛被归纳为三个连续阶段。
