Electrospinning-induced shape memor

Electrospinning-induced shape memory effect in thermoplastic polyurethane characterization and thermoviscoelastic modeling.
Electrospun thermoplastic polyurethane (TPU) nanofibers are known to contract considerably (∼40%) on heating up to ∼90 °C. This study investigates this thermomechanical behavior and the TPU shape memory capabilities. The shape memory effect was first studied in TPU films as a model system by applying classical thermomechanical cycles (programming and recovery). The films were able to fix the applied deformation during long-term storage at room temperature, well above the material's calorimetric glass transition temperature and in the absence of a percolated structure of hard domains. Structural analysis (Fourier transform infrared, differential scanning calorimeter, and dynamic mechanical analysis) revealed broad thermal transitions indicating the presence of a mixed phase of hard segments dispersed in the soft segment matrix. Using a linear viscoelastic model together with time–temperature superposition, the shape memory effect was attributed to the thermoviscoelastic properties of TPU. In particular, the mixed phase was found to give rise to a very broad relaxation spectrum dominated by long relaxation times, which explains the suppression of strain recovery at room temperature. Finally, the electrospinning process was examined and was found to be similar to a programming cycle characterized by the strong elongation flow accompanied by massive solvent evaporation, whereas the contraction effect was interpreted as the recovery phase in a shape memory perspective. Thus, the contraction of electrospun TPU mats may be considered to be an electrospinning-induced shape memory effect.

結果 (中文) 1:

静电纺丝致形状记忆效应在热塑性聚氨酯表征和黏弹性建模。电纺纳米纤维热塑性聚氨酯 (TPU) 已知合同大大 (∼40%) 加热到 ∼90 ° c。这种形变行为和 TPU 形状记忆能力进行了研究。形状记忆效应是第一次在 TPU 薄膜作为模型系统应用研究古典热力循环 (编程和恢复)。电影是能够在室温，远远高于材料的热玻璃化转变温度和硬磁畴渗出式结构没有修复长期贮藏过程中的应用的变形。结构分析 (傅里叶变换红外、 差示扫描量热仪和动态力学分析) 显示广泛的热转换指示在软段基体中分散的硬段混相的存在。使用时间 — — 温度叠加线性粘弹性模型，归功于 TPU 的黏弹性特性的形状记忆效应。尤其是，混合的相位被发现引起非常广泛的弛豫谱由长的弛豫时间，这也解释了在室温应变复苏的制止。最后，静电纺丝过程检查和发现要类似于编程周期特点强伸长流伴随着大量的溶剂蒸发，而收缩效应被解释为形状记忆角度的恢复阶段。因此，静电纺丝 TPU 垫的收缩可能会认为是静电纺丝致形状记忆效应。

結果 (中文) 3:

静电致形状记忆效应的热塑性聚氨酯的特性和粘弹性模型。
电纺纳米纤维的热塑性聚氨酯（TPU）是已知的合同相当（∼40%）在加热到90∼°这研究的热力学行为和聚氨酯形状记忆功能。首先是在TPU薄膜利用经典热机循环模型系统研究了形状记忆效应（编程和恢复）。薄膜能够解决应用变形在长期储存在室温下，远高于材料的玻璃化转变温度和热的渗出的结构硬磁畴的缺失。结构分析（傅里叶变换红外，差示扫描量热仪，动态力学分析）揭示了广泛的热转换，表明在软链段矩阵的混合相的存在下，分散的硬链段。用线性粘弹性模型与时间-温度叠加，形状记忆效应是由于聚氨酯的粘弹性性质。特别是，在混合相被发现引起一个非常广泛的弛豫时间，这解释了在室温下的应变恢复控制的松弛谱。最后，的静电纺丝过程中被检查，被发现是类似的一个编程周期，其特征是强烈的伸长流动伴随着大量的溶剂蒸发，而收缩效应被解释为在形状记忆的角度的恢复阶段。因此，静电TPU垫的收缩可能会被认为是一个静电致形状记忆效应。