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Microfluidic Preparation of Liquid Crystalline Elastomer Actuators
Published on: May 20, 2018
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在形状记忆聚氨中微裂的核化,发展和愈合,经过随后的张力循环
Maria Staszczak1, Leszek Urbański1, Arkadiusz Gradys1
1Institute of Fundamental Technological Research, Polish Academy of Sciences, 02-106 Warsaw, Poland.
Polymers
|July 13, 2024
概括
这项研究表明,热塑性聚氨形状记忆聚合物 (PU-SMPs) 中的微裂在高于其玻璃过渡温度的热恢复过程中愈合. 循环负荷最初会导致微裂,但它们会自我修复,尽管过度循环可能会导致永久性损伤.
科学领域:
- 材料科学 材料科学 材料科学
- 聚合物科学 聚合物科学
- 机械工程 机械工程
背景情况:
- 热敏形状记忆聚合物 (SMP) 在机械变形后通过温度变化恢复原始形状.
- 变形导致SMP中的微裂,影响其结构完整性和恢复.
- 了解微裂变的演化和愈合对于SMP应用至关重要.
研究的目的:
- 研究循环拉伸负荷和热回收对热塑性聚氨形状记忆聚合物 (PU-SMP) MM4520.20的微观结构的影响.
- 分析机械负荷时形成的微裂的愈合.
- 将微观结构变化与宏观形状记忆行为相关联.
主要方法:
- 使用扫描电子显微镜 (SEM) 进行PU-SMP微结构的表征.
- 通过动态机械分析 (DMA) 和差分扫描热量计 (DSC) 分析材料性能和相位过渡.
- 使用广角X射线散射 (WAXS) 评估结构变化.
- 评估形状记忆性能 (固定性和恢复性).
主要成果:
- 在第一个拉力加载-卸载周期期间,PU-SMP表面上产生微裂.
- 随后加热在玻璃过渡温度 (Tg = 45 °C) 以上,可以有效地治愈这些微裂.
- 在多达五个周期中,在变形过程中出现了自我愈合或裂关闭;然而,在八个周期中,裂愈合需要热回收,这表明永久损伤的关键周期数.
结论:
- 热力学循环显著影响PU-SMP微结构,在热回收过程中发生微裂纹愈合.
- PU-SMP表现出极好的形状记忆特性 (99%的固定性,92%的恢复).
- 了解机械负荷,热处理和微观结构之间的相互作用是优化SMP性能和耐用性的关键.
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