超临界CO2发泡技术精制TPU泡沫材料：泡孔结构、硬段结构对力学性能的影响研究

Supercritical CO2 Forming of TPU Foam Materials： Correlations of Cell Structure， Hard Segment Structure， and Properties

摘要:

热塑性聚氨酯弹性体（TPU）是热塑性弹性体（TPE）的代表，具有优异的回弹性、可熔融再加工、耐久性、耐磨性、柔韧性和拉伸性能等优点。TPU可根据化学结构差异分为芳香族、脂肪族和脂环族三类。物理发泡技术制备的轻质TPU泡沫，具有吸能减震、隔热等特性，在3C电子、运动防护、汽车制造、生物医学等领域应用广泛。然而，现有报道缺乏对其泡孔结构、硬段化学结构与弹性性能之间系统性关联的研究，制约了高性能TPU泡沫的开发和实际应用。利用超临界CO₂物理发泡技术，制备了2种不同泡孔结构的TPU泡沫材料。采用红外光谱、核磁共振氢谱和扫描电镜技术表征了其微观泡孔与化学结构，采用差示扫描量热法分析了其热行为差异，利用万能试验机、回弹仪评估了其循环压缩性能和回弹率。结果表明，TPU泡孔尺寸及密度主要受饱和压力的调控，而其膨胀倍率主要依赖于饱和温度。随着饱和压力的增加，泡孔尺寸显著降低。TPU泡沫的压缩强度与泡孔尺寸成反比，压缩回弹性随泡孔尺寸的减小而增大。泡沫的压缩强度随膨胀倍率的增大而显著降低，而其压缩回弹性则随膨胀倍率的增大先上升后降低。TPU硬段分子结构的对称性对力学性能影响显著，使得脂肪族TPU泡沫的压缩强度和回弹性相较于芳香族TPU泡沫均有提高，最高提高了160%和82%。本研究深化理解了TPU微孔发泡材料的泡孔结构与硬段化学结构对其力学性能及回弹性的影响，为工业领域制备性能优异、成本效益高、功能更为复杂的TPU泡沫材料提供了理论基础。

Abstract:

This study meticulously prepared thermoplastic polyurethane elastomer （TPU） foam materials with diverse cell structures utilizing supercritical CO? physical foaming technology and conducted an in-depth investigation of the systematic relationship between cell structure， hard segment chemical structure， and elastic properties. Through Fourier transform infrared spectroscopy （FTIR）， proton nuclear magnetic resonance （1H-NMR）， and scanning electron microscopy （SEM）， the chemical and microscopic cellular structure characteristics of TPU were comprehensively revealed. Comparative analysis using differential scanning calorimetry （DSC） highlighted the thermal behavior differences between two TPU materials. In addition， the cyclic compression performance and resilience of TPU foam materials were meticulously evaluated and quantitatively analyzed using a universal testing machine and a rebound tester. The results indicate that cell size and density are primarily regulated by saturation pressure， while the expansion ratio is mainly dependent on the saturation temperature. As the saturation temperature increases， the cell size initially enlarges and then diminishes， though the temperature's impact on cell size is relatively limited. The compressive strength of TPU foam is inversely proportional to cell size， and compressive resilience increases as the cell size decreases. The compressive strength of the foam significantly decreases with an increase in the expansion ratio， while the compressive resilience initially rises and then diminishes with an increase in the expansion ratio. The symmetry of the TPU hard segment molecular structure significantly influences mechanical properties， resulting in a maximum increase of 160% and 82% in compressive strength and resilience， respectively， for H-TPU foam compared to M-TPU foam. The findings of this study not only provide insights into the impact of cell structure and hard segment chemical structure on the mechanical properties and resilience of TPU microcellular foaming materials but also offer a theoretical foundation for the industrial fabrication of TPU foam materials with superior performance， cost-effectiveness， and complex functionalities.