Department of Forest Biomaterials, North Carolina State University, Campus Box 8005, Raleigh, North Carolina 27695-8005, USA.
Biomacromolecules. 2010 Sep 13;11(9):2471-7. doi: 10.1021/bm1006689.
The effect of humidity on the morphological and thermomechanical properties of electrospun poly(vinyl alcohol) (PVA) fiber mats reinforced with cellulose nanocrystals (CNs) was investigated. Scanning electron microscopy (SEM) images revealed that the incorporation of CNs improved the morphological stability of the composite fibers even in high humidity environments. Thermal and mechanical properties of the electrospun fiber mats were studied by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and large deformation tensile tests under controlled humidity and temperatures. The balance between the moisture-induced plasticization and the reinforcing effect of rigid CN particles was critical in determining the thermomechanical behaviors of the electrospun fiber mats. Results indicated that the stabilizing effect of the CNs in the PVA matrix might be compromised by water absorption, disrupting the hydrogen bonding within the structure. The amount of this disruption depended on the surrounding humidity and the CN loading. The reduction in tensile strength of neat PVA fiber mats as they were conditioned from low relative humidity (10% RH) to high relative humidity (70% RH) was found to be about 80%, from 1.5 to 0.4 MPa. When the structure was reinforced with CNs, the reduction in strength was limited to 40%, from 2 to 0.8 MPa over the same range in relative humidity. More importantly, the CN-loaded PVA fiber mats showed a reversible recovery in mechanical strength after cycling the relative humidity. Finally, humidity treatments of the composite PVA fiber mats induced significant enhancement of their strength as a result of the adhesion between the continuous matrix and the CNs.
湿度对静电纺丝聚乙烯醇（PVA）纤维垫的形态和热机械性能的影响进行了研究，其中纤维垫中加入了纤维素纳米晶体（CNs）。扫描电子显微镜（SEM）图像表明，即使在高湿度环境下，加入 CNs 也能提高复合纤维的形态稳定性。通过使用差示扫描量热法（DSC）、动态力学分析（DMA）和在控制湿度和温度下的大变形拉伸试验，研究了静电纺丝纤维垫的热机械性能。水分诱导增塑与刚性 CN 颗粒增强效果之间的平衡对于决定静电纺丝纤维垫的热机械行为至关重要。结果表明，CN 在 PVA 基体中的稳定作用可能因吸水而受到影响，破坏了结构内的氢键。这种破坏的程度取决于周围的湿度和 CN 的负载量。当相对湿度从低（10%RH）到高（70%RH）时，纯 PVA 纤维垫的拉伸强度从 1.5MPa 降低到 0.4MPa，降低了约 80%。当结构中加入 CNs 时，强度降低限制在 40%，从 2MPa 降低到 0.8MPa，相对湿度范围相同。更重要的是，在相同的相对湿度循环范围内，负载 CN 的 PVA 纤维垫的机械强度具有可恢复的恢复能力。最后，由于连续基质与 CNs 之间的粘附作用，复合 PVA 纤维垫在湿度处理后其强度得到显著提高。
