【作者】 钟萍；

【导师】 李健；

【作者基本信息】 机械科学研究总院 ， 机械设计及理论， 2009， 博士

【摘要】 针对我国水电建设中水工建筑混凝土结构防护问题,研究聚脲涂层在水工建筑混凝土结构防护应用的可行性和技术关键;在深入分析水工建筑混凝土结构抗泥沙水流冲蚀破坏现象和聚脲涂层特性的基础上,针对涂层耐磨性和在混凝土基体上的附着强度要求,研制聚脲涂料和聚天冬氨酸酯涂料,设计出适合于混凝土表面防护的复合聚脲涂层体系;通过模拟水工环境条件下的冲蚀磨损试验和湿附着力试验,以及物理化学性能试验和表面分析,探讨高速含水沙流冲蚀条件下的涂层磨损和附着机理,为聚脲涂层在实际水工环境中的应用提供理论支撑。其主要研究内容与结论如下:1、针对水工建筑表面抗冲蚀保护的特殊需要出发,深入研究了聚脲A、B组分的材料和制备工艺及其与涂层性能之间的关系,开发出一种新的聚脲涂料。所研制的聚脲涂料的A组分外观无色透明,粘度、凝胶时间和NCO值能与氨基化合物(B组分)配套性能好,并提高了涂层伸长强度、伸长率。2、采用国产原料(聚环氧丙烷二胺和顺丁烯二酸二乙酯)合成了聚天冬氨酸酯,利用核磁共振氢谱、红外光谱、DSC曲线表征了聚天冬氨酸酯及其涂层的结构,优化了合成反应工艺。试验研究了用所合成的聚天冬氨酸酯制备的聚脲涂层的各项理化性能,制备的聚脲涂层固化时间较长、涂层施工方便、不需要特殊的喷涂设备,涂层能与基材充分润湿,具有优异的附着力,同时涂层还具优异的机械物理性能和耐化学介质性能。对聚天冬氨酸酯聚脲涂层的摩擦学性能研究发现,不论是在冲蚀条件下还是固定磨料干摩擦条件下的耐磨损性能都不及常规聚脲涂层。3、深入研究了聚脲涂层的摩擦学性能,首次运用高速含沙水射冲蚀磨损试验机评价聚脲涂层的泥沙冲蚀磨损性能,探讨了聚脲涂层的磨损机理。研究发现:(1)聚脲涂层成分对涂层耐冲蚀磨损性能影响主要体现在聚氨酯/聚脲涂层制备过程中产生的气泡影响,通过调整材料组分和施工工艺减少涂层中气泡是提高其耐磨性能的关键。(2)聚脲涂层具有比聚氨酯/聚脲混合体系涂层更优越的磨损性能,固定磨料干摩擦条件下和高速含水砂流冲蚀条件下都具有优异的抗冲蚀性能,而且对冲蚀角的敏感性有所改善。(3)在固定磨料干摩擦条件下,喷涂聚脲表面存在氧化磨损过程,而在高速含沙水射流条件下不易发生氧化磨损。(4)聚脲涂层在一定的温度范围内,具有较高的阻尼性和刚性,热稳定性高,能经受涂层高内耗产生的热能,并及时传递给试验流体,从而使涂层具有优异的耐冲蚀磨性能。(5)根据Bitter的塑性材料冲蚀理论建立了聚脲冲蚀磨损模型,描述了韧性材料在不同冲蚀角度和速度下的冲蚀行为,提出聚脲涂层在冲蚀角度31.5°时切削磨损量最大、冲蚀角度接近90°时变形磨损最大的冲蚀磨损规律。4、将湿附着力测试方法应用到聚脲涂层与混凝土的附着强度测试和研究中,获得了重要的科学数据,为表征聚脲涂层与混凝土的附着强度寻求到较好的解决方案。通过选择液体环氧树脂、活性稀释剂和固化剂开发出一种附着性能优异的无溶剂环氧封闭涂料,克服了聚脲涂料因快速成型而在基材表面润湿不充分导致粘附不强的缺陷,显著提高了聚脲涂层体系与混凝土之间的附着强度。利用表面形貌、红外光谱、电子能谱等手段,深入分析了混凝土与聚脲涂层界面特性,探讨了聚脲涂层在混凝土表面附着失效的机理。发现聚脲涂层与混凝土的附着失效为涂层与混凝土之间的物理附着破坏;而“无溶剂环氧封闭涂层+聚脲涂层”聚脲涂层体系的失效为封闭涂层与混凝土之间的物理附着破坏和封闭涂层本身的内聚破坏;封闭涂层的应用可提高混凝土表面的强度。5、综合聚脲涂层的优异耐冲蚀性能与聚天冬氨酸酯聚脲涂层的优异附着性能,提出在混凝土试样表面制备“聚天冬氨酸酯涂层+聚脲涂层”复合聚脲涂层体系作为水工建筑混凝土的保护涂层体系。表面分析和摩擦学性能试验证实:复合聚脲涂层体系具有良好的耐冲蚀磨损性能,采用复合聚脲涂层体系防护是水工建筑混凝土结构抗冲蚀磨损的有效手段和措施。研究发现,聚天冬氨酸酯聚脲作为封闭底涂层的复合聚脲体系,附着力明显高于单一聚脲涂层的附着力,封闭涂层渗入到粗糙混凝土表面使涂层体系获得良好的附着力,同时增强了混凝土表层的强度,保持冲蚀试验后涂层附着力基本不降低。由于聚天冬氨酸酯聚脲底涂层具有比无溶剂环氧底涂层更高的韧性,以及与聚脲涂层的良好匹配性,因此复合聚脲涂层体系比“无溶剂环氧封闭涂层+聚脲涂层”聚脲涂层体系更适合用做水工环境混凝土的表面防护。更多还原

【Abstract】 Towards the protection of concrete structures of hydraulic architecture in hydropower construction of China, the feasibility and the key technology of the application of polyurea coatings to the protective concrete structures of hydraulic construction are studied. Based on the deep analysis of anti-sediment-flow erosion of concrete structures of hydraulic architecture and the properties of polyurea coatings the coatings of polyurea and polyaspartic ester are developed, and the composite coating systems are designed, which are suitable for the protection of concrete surface, according to the requirements of wear resistance and adhesion strength in the concrete surface; Through a series of mock tests (including the erosion, wet adhesion, physical and chemical properties and surface analysis) under the hydraulic conditions, the wearing and adhesion mechanism of these coatings under the condition of erosion by sand aquifer flow at a high speed are discussed. The main contents and the significant new results are shown as follows:1. From the special demand of anti-erosion protection of hydraulic construction surface, the ingredients of polyurea A, B components, their preparation, and their relationship with the performance of the coatings are studied intensively. Thereby, a new polyurea coating has been developed. The mechanical and physical properties of the new polyurea coating are excellent.2. The polyaspartic acid ester by the use of the domestic raw materials (poly propylene oxide diamine and diethyl maleate) is synthesized. The structure of polyaspartic acid ester and its coating are characterized by using NMR, IR and DSC curves, and the synthesis process is optimized. The polyaspartic acid ester coating has good adhesion, mechanical physical and chemical media properties. However, its wear-resistant performance is not good as the conventional polyurea coatings in the erosion wear conditions or dry conditions.3. The tribological properties of the polyurea coatings are studied intensively. The erosion performances of the coatings are evaluated by using the high pressure jet impact erosion testing machine firstly, and the erosion mechanism is explored. Studies showed: (1) The effect of polyurea coating compositions on erosion-resistant performance of the coatings is mainly reflected in the influence of bubbles arising during the preparation of the polyurethane-urea coatings. The key to improve their wear resistance is to decrease the bubbles of the coatings by adjusting the material compositions and spray process. (2) The polyurea coatings have superior wear performance than polyurethane/polyurea hybrid coating systems and display an excellent performance of anti-erosion under both conditions of dry friction and erosion and also an improved sensitivity on the erosion angle. (3) Under the dry-friction condition, the oxidation-wear process occurs on spray polyurea surface, while such a process does not easily happen under the high-speed water jet sandy condition. (4) The polyurea coating is provided with higher damping, hardness and thermal stability, which makes it withstand the heating created by high inner friction; the heat can be transmitted to the test fluid in time so that the coating has an excellent wear-resistance performance. (5) On the basis of Bitter’s erosion theory of ductile materials, the erosion model of polyurea is established, the erosion behaviors of ductile materials at different impact angle and velocity are described, and the erosion law is also proposed, which holds that the maximal cutting wear is at the impact angle about 31.5°and the maximal deformation wear at the impact angle close to 90°.4. The wet-adhesion measurement was first applied to measure the adhesion strength of the polyurea coating on the surface of concrete, which provides important scientific data and finds a better solution to characterize the adhesion strength between the polyurea coating and the concrete surface. The solvent-free epoxy sealing coating is developed with an excellent adhesion by choosing liquid epoxy resin, reactive diluents and curing agent. This solvent-free epoxy sealing coating improves the adhesion of the coating system and enhances the strength of the concrete surface. The failure of the adhesion resulted from the damage of the physical adhesion between the polyurea coating and concrete. However, the failure of "solvent-free epoxy sealing coating + polyurea coating" system results from both the damage of the physical adhesion between the coating and concrete and the damage of cohesion of the sealing coating itself.5. The "polyaspartic acid ester + polyurea coating" composite polyurea coating system on the surface of the concrete sample was proposed and prepared firstly as the protective coating system of hydraulic concrete construction. The polyaspartic acid ester coating can enhance the adhesion of the coating system and the strength of the concrete surface. The composite polyurea coating system exhibits an excellent erosion resistance so as to be more suitable for the protection against the erosion under the hydraulic condition.更多还原