Abstract:

Polyurethane (PU) has received a lot of attention due to its high degree of freedom in performance adaptation. However, its diverse properties have led researchers to disagree on the effects of modifying the high and low temperature rheological properties of PU-modified asphalt. Therefore, it is crucial to gain a deeper understanding of the connection between different PU raw material properties, synthesis processes, product structures and the high and low temperature properties of modified asphalt. Based on the chemical modification mechanism of PU, combined with the molecular formation process and the performance evaluation criteria of polymer modified asphalt, this paper systematically explores the properties of different types of soft and hard segments and the structure of PU modifiers prepared by different synthesis methods on modified asphalt. It was shown that the degree of physical and chemical cross-linking of PU molecules within the asphalt is a key factor in the improvement of performance: the nature of the soft and hard segments and the molecular structure mainly affects the microstructural stability of the physical cross-linking, while the content of the isocyanate group directly determines the strength and complexity of the chemical cross-linking. The composite system of PU with polymers and other modifiers in asphalt was further analyzed for the modified mechanism. The addition of modifiers enhances the performance by changing the structural distribution of the internal components of asphalt with PU. However, it is difficult to accurately quantify the degree of cross-linking of PU through the microstructure in the current study, which restricts the precise tuning of the synthesis parameters and processes, which in turn leads to a low predictability of the modification effect. In addition, the structural instability of the composite system and the weak chemical interaction between modifiers often triggered the decrease of storage stability or the deterioration of certain properties. Finally, the development trend and outlook of the research on PU and its composite modified asphalt are proposed.

Key words: polyurethane, modified asphalt, rheological properties, polymers, elastomer, composites, synthesis

摘要：

聚氨酯（PU）因其性能调整自由度高而受到广泛关注。然而，其多样的性质导致学者在PU改性沥青的高低温流变性能改性效果上存在分歧。因此深入了解不同PU原料特性、合成工艺、成品结构与改性沥青高低温性能间的联系至关重要。基于PU的化学改性机理，结合分子形成过程与聚合物改性沥青的性能评价标准，系统探讨了不同种类软硬段的性质以及不同合成方法制备的PU改性剂的结构对于改性沥青的影响。研究表明，PU分子在沥青内部的物理交联与化学交联程度是性能改善的关键因素：软硬段性质及分子结构主要影响物理交联的微观结构稳定性，而异氰酸酯基团的含量直接决定了化学交联的强度和复杂性。进一步分析了PU与聚合物及其他改性剂的复合体系在沥青中的作用机理。外加改性剂通过改变沥青的内部组分与PU的结构分布来提升性能。然而，目前研究尚难通过微观结构精准量化PU的交联程度，这限制了合成参数与工艺的精确调控，进而导致改性效果的可预测性较低。此外，复合体系结构不稳定、改性剂间化学作用微弱等问题往往引发储存稳定性下降或某些性能劣化。最后，提出了PU及其复合改性沥青研究的发展趋势与展望。

关键词: 聚氨酯, 改性沥青, 流变性能, 聚合物, 弹性体, 复合材料, 合成