Xie Chao, Shi Yufeng, Si Zhuozhuo, Wu Ping, Sun Binqiang, Ma Wenzhe
Civil Engineering Department, Lanzhou Jiaotong University, Lanzhou 730070, China.
CSCEC AECOM Consultants Co., Ltd., Lanzhou 730000, China.
Polymers (Basel). 2024 Dec 18;16(24):3529. doi: 10.3390/polym16243529.
This study investigates the effect of microstructural changes in polyurethane coatings on their water resistance properties. Polyurethane coatings with varying diluent contents were prepared and tested for water penetration resistance and mechanical property retention. The time-dependent behavior of water within the coatings at different immersion durations was analyzed using low-field nuclear magnetic resonance (NMR). Furthermore, the free volume and characteristic molecular groups of each coating were analyzed using microscopic techniques, including positron annihilation lifetime spectroscopy (PALS) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). Results indicate that diluent content significantly alters the microstructure of the coatings. With increasing diluent content, both the average pore volume and free volume fraction initially decrease and then increase, while characteristic molecular groups, including hydrophilic groups, gradually decline. The water resistance performance of the coatings was significantly influenced by the combined effects of free volume and characteristic molecular groups. Among the five tested coating formulations, coatings with diluent contents of 20% and 25% showed a superior water penetration resistance, higher retention of mechanical properties after immersion, and relatively low total content of bound and free water at all immersion ages. The entropy weight method and the equal weight method were used to assess the overall water resistance, with the following ranking of scores: > > > > . This study offers theoretical support to guide the design and practical application of polyurethane coatings in real-world engineering projects.
本研究考察了聚氨酯涂层微观结构变化对其耐水性的影响。制备了具有不同稀释剂含量的聚氨酯涂层，并对其耐水渗透性和力学性能保持率进行了测试。使用低场核磁共振（NMR）分析了不同浸泡时间下涂层内水随时间的行为。此外，使用包括正电子湮没寿命谱（PALS）和衰减全反射傅里叶变换红外光谱（ATR-FTIR）在内的微观技术分析了每种涂层的自由体积和特征分子基团。结果表明，稀释剂含量显著改变了涂层的微观结构。随着稀释剂含量的增加，平均孔体积和自由体积分数最初降低，然后增加，而包括亲水基团在内的特征分子基团逐渐减少。涂层的耐水性能受到自由体积和特征分子基团综合作用的显著影响。在测试的五种涂料配方中，稀释剂含量为20%和25%的涂层表现出优异的耐水渗透性、浸泡后较高的力学性能保持率以及在所有浸泡龄期相对较低的结合水和自由水总含量。采用熵权法和等权法对整体耐水性进行评估，得分排序如下：> > > > 。本研究为指导聚氨酯涂层在实际工程项目中的设计和实际应用提供了理论支持。
