路用聚氨酯胶结料的抗紫外老化性能

路用聚氨酯（PU）胶结料在工程应用中不可避免地会遭受紫外照射的影响。为此，采用紫外老化试验箱模拟自然老化过程，以影响路用性能的拉伸性能和黏弹性（基于温度扫描和频率扫描的动态热力学性能）为评价指标，研究老化下路用PU胶结料性能的演化规律，并通过红外光谱和电子扫描显微镜揭示其老化机理；同时，通过调整PU的组分配比（多元醇/异氰酸酯的质量比为100/80，100/65，分别记为PU-Ⅰ，PU-Ⅱ），揭示不同异氰酸酯组分含量对PU紫外老化性能的影响规律与机理。试验表明：紫外老化对PU拉伸强度和断裂伸长率的影响主要表现在老化前期，老化中后期性能保持相对稳定甚至有所回升，如PU-Ⅰ的残余强度在老化28 d后恢复至98.8%；紫外老化并未明显降低PU的拉伸模量，反而提高了其拉伸模量，如老化28 d后PU-Ⅰ的拉伸模量提升了近一倍；紫外老化提高了PU的储能模量和玻璃化转变温度（T_g），增大了低频区PU的复数模量和黏弹比，降低了中高频区PU的复数模量和黏弹比，特别是PU-Ⅰ。上述PU性能的演化机理主要包括塑化、分子链断裂和物化交联，其中物化交联主要包括较强氢键形成而产生的物理交联、后固化以及水分子与未反应的-N=C=O官能团反应而引起的化学交联；异氰酸酯含量的适当增加，增强了物化交联作用，可以提高PU的抗老化能力。总之，研究成果为PU胶结料在道路工程领域中的应用奠定了一定的基础。

Anti-ultraviolet Aging Performance of Polyurethane Binders Used in Roads

Polyurethane (PU) binders are inevitably affected by ultraviolet (UV) irradiation in engineering applications. Given this, the tensile properties and viscoelasticity (dynamic thermomechanical performance based on temperature and frequency scanning) that affect road performance were considered as the evaluation indexes. This was done to study the evolution law relating to the performance of PU binders used in roads under UV aging, using a UV aging chamber to simulate the natural aging process. The aging mechanism was revealed via scanning electron microscopy (SEM) and the infrared (IR) spectrum. Additionally, the influence law and mechanism of different isocyanate contents relating to the UV aging performance of PU was revealed by adjusting the ratio of the components of PU (the mass ratios of polyol/isocyanate are 100/80 and 100/65 and are denoted as PU-Ⅰ and PU-Ⅱ, respectively). The tests show that UV aging has the most significant impact on the tensile strength and elongation at the break of the PU in the early stage of aging, followed by a relatively stable impact on its performance in the middle and later stages of aging. For example, the residual strength of PU-Ⅰ recovered to 98.8% after a 28-day aging process. The UV aging did not significantly reduce the tensile modulus of the PU. However, it increased the tensile modulus, given that the tensile modulus of PU-Ⅰ nearly doubled after 28 days of aging. The UV aging enhanced the storage modulus and glass transition temperature (T_g) of the PU, increased the complex modulus and viscoelastic ratio in the low-frequency region, and decreased their value in the middle and high-frequency regions, particularly for PU-Ⅰ. The above evolution mechanisms of the performance of PU mainly include plasticization, molecular chain fracture, and physicochemical crosslinking. Moreover, the physiochemical crosslinking primarily includes physical crosslinking resulting from the formation of strong hydrogen bonds, and chemical crosslinking resulting from the post-curing and the reaction between water molecules and the unreacted -N=C=O functional groups. The study findings indicate that increasing the isocyanate content enhances the physicochemical crosslinking effect, which improves the aging resistance of the PU. Therefore, the research results have laid the foundation for the application of PU-binders in road engineering.