【作者】 邵春明；

【导师】 徐国跃；

【作者基本信息】 南京航空航天大学 ， 材料加工工程， 2010， 博士

【摘要】 随着红外探测技术的提高,红外隐身材料研发和应用的重要性与日俱增。红外隐身涂层由于其突出的优点,成为红外隐身材料中最重要的品种之一。而如何设计和制备具有低红外发射率及优良工程应用性能的红外隐身涂层成为关键。本文通过理论计算和分析,设计了低红外发射率涂层(LIREC)的理想组成及结构;设计了含片状粒子涂层对辐射吸收的物理模型,并推导出了其红外发射率的计算公式;通过设计相关实验对结论加以验证。选择红外高透明的三元乙丙橡胶(EPDM)和红外低透明的聚氨酯(PU)两种典型树脂为代表,分别对其改性作为黏结剂,制备LIREC。研究LIREC的组成结构与涂层的红外发射率性能、力学性能、耐盐水腐蚀性能和耐老化性能的关系,为LIREC的研制提供基础性指导。主要内容包括:(1)LIREC的组成和结构设计:通过理论计算和分析,研究了颜料粒子的材质、形状、在涂层中的分布状态及涂层表层黏结剂的红外透明性和厚度对涂层红外发射率的影响,进而设计了LIREC的理想组成及结构。设计了含片状粒子涂层对辐射吸收的物理模型,并推导了其红外发射率的计算公式。(2)涂层的组成结构与红外发射率性能研究通过设计相关实验对理想LIREC的设计结论加以验证。结果证明:通过①选用金属类的片状粒子颜料;②红外高透明性黏结剂;③将黏结剂改性提高极性,以增强其与金属颜料的相容性;④通过一定的工艺条件,使薄片状颜料粒子整齐紧凑地平铺在涂层表面等措施,可以显著降低涂层的红外发射率。并可成功制备出红外发射率低至0.1左右的LIREC。通过制备不同附着率的片状Cu粉颜料,调节红外涂层表面黏结剂的厚度,从而调节涂层的红外发射率。当选用高附着率的片状Cu粉颜料时,黏结剂红外透明性对涂层红外发射率的影响大幅度降低,即使使用红外透明性较差的黏结剂也可制得LIREC。大大拓宽了黏结剂的选择范围,为研制性能优良的LIREC打下了坚实的基础。通过实验对含片状粒子涂层红外发射率的计算公式进行验证。证明该公式可以近似的计算含片状粒子涂层的红外发射率,并能反映影响涂层红外发射率的主要因素的影响情况。(3)LIREC的组成结构与力学性能研究:分析了EPDM接枝的极性基团、颜料含量、黏结剂分子链结构对LIREC力学性能的影响。表明LIREC可经组成结构设计提高其力学性能:1)低极性黏结剂接枝强极性基团。XPS分析证明EPDM-g-MAH中的极性基团可与金属材料形成配位键,显著提高LIREC的力学性能。2)调控颜料的含量。随颜料含量的增加:涂层的附着力增大;硬度先提高后下降;柔韧性和耐冲击强度方面,使用刚性链为主黏结剂的涂层会显著降低,而对使用柔性链为主黏结剂涂层的影响较小。3)调节黏结剂的分子链结构。柔性EPDM-g-MAH制备的LIREC的柔韧性和耐冲击强度好于刚性PU所制备的,而硬度有所不及。PU用附着力和韧性更好的环氧改性后制备的LIREC的柔韧性和耐冲击强度显著提高,而附着力和硬度仍然优良。(4)LIREC的组成结构与耐盐水腐蚀性能研究研究了LIREC在盐水中的腐蚀机理和腐蚀进程。结果表明,LIREC的腐蚀失效主要由于Cu粉颜料发生腐蚀引起涂层红外发射率大幅上升造成的。黏结剂可对颜料提供保护,延缓腐蚀。在腐蚀前期,黏结剂的耐渗水性能起主要作用,耐渗水性好,可减缓腐蚀溶液的渗透;而到腐蚀的中后期,黏结剂对颜料的附着力起主要作用,附着力强则能减缓二者界面处的起泡进展。分别对EPDM和PU进行改性作为黏结剂,制备LIREC。研究不同LIREC的组成结构与其耐盐水腐蚀性能的关系。结果表明,LIREC可通过组成结构设计提高其耐腐蚀性能:1)低极性黏结剂接枝强极性基团。EPDM经改性提高极性后显著改善其与金属颜料的相容性和附着力,降低了涂层孔隙率,从而提高了LIREC的耐腐蚀性能。2)通过黏结剂的组分和结构设计,引入强耐腐蚀性组分,但要考虑各组分间的表面张力匹配。PU中引入与金属颜料附着力更强、耐腐蚀性能好的环氧树脂可显著提高LIREC的耐腐蚀性能;而引入耐腐蚀性能强、但表面张力相差太大的含氟组分与环氧树脂时,LIREC的耐腐蚀性能变差。3)提高LIREC的致密度,减少空隙。EPU的研究表明,适当的组分配比、环氧种类及固化温度可提高黏结剂的交联固化程度、减小结构孔隙;而适当的消泡剂用量和固化温度可减少由气泡和溶剂挥发所造成的气孔。4)耐腐蚀性能强的黏结剂制备的LIREC的耐腐蚀性能并不一定强。要综合考虑其所需的颜料添加量、抗渗透性能及与颜料的附着性能,其中与颜料的附着性能更为重要。5)在LIREC上涂覆红外高透明性的防护型面漆。在EPU/50%Cu涂层上涂覆一层可阻隔腐蚀介质渗透的EPDM-g-MAH面漆,其发射率增大较小,但耐盐水腐蚀性能却大幅提高。(5)LIREC的组成结构与耐热老化和光老化性能研究研究了不同LIREC的耐热老化性能。结果表明,LIREC经热老化引起红外发射率升高的原因是其中的Cu粉颜料发生氧化。而黏结剂可对颜料提供一定保护,延缓其氧化进程,与颜料相容性好、附着力强的黏结剂的保护性能更好。EPDM-g-MAH/20%Cu、EPU/50%Cu及EPDM-g-MAH@EPU/50%Cu涂层的耐热老化性能较好,可在433K以下长时间使用。研究了不同LIREC的耐紫外人工加速老化性能。结果表明,随着时间的延长,LIREC发生了失光和变色现象,其红外发射也率逐渐升高。黏结剂组分间相容性差,会加速老化。减少黏结剂中易紫外降解组分的含量能提高涂层的耐光老化性能。LIREC耐紫外人工加速老化性能的优劣顺序为: FPU/50%Cu > PU/50%Cu > EPDM-g-MAH/20%Cu > EPU/50%Cu >EPDM-g-MAH@EPU/50%Cu,与其所用的黏结剂的耐光老化性能一致。更多还原

【Abstract】 With the improvement of infrared detection technology, the importance of the development and application of infrared stealth materials increases. Due to its outstanding advantages of infrared stealth coating, as infrared stealth coating, it is one of the most important species. But how to design and prepare infrared stealth coatings which has low infrared emissivity and the excellent performance of engineering applications becomes the key factor.In this paper, the ideal composition and structure of low infrared emissivity coating (LIREC) was designed by theoretical calculation and analysis, the physical model of radiation absorbing of containing flake particles of coating was designed, its infrared emissivity approximate calculation formula was derived, and the related experiments on the conclusions was designed and verified. High infrared transparency of EPDM rubber and low infrared transparency of polyurethane were choosed for two typical representatives, which were modified as resin-based material, and LIREC was prepared. The composition and structure of LIREC on infrared emissivity performance, mechanical properties, corrosion resistance and anti-aging properties of LIREC was studied, providing the basic guidance for LIREC. The main contents include:(1) The composition and structure design of LIREC:Through theoretical calculation and analysis, the effects of the pigment material, shape of pigment particles, the distribution of pigment particles in the coating and infrared transparency and thickness of the surface coating resins on infrared emissivity of coating were researched, and thus the ideal composition and structure of LIREC were designed. The physical model of radiation absorbing of coating containing flaky particles was designed and the infrared emissivity approximate formula was derived.(2) Study of the composition and structure on the infrared emissivity of coating:The related experiments were designed to validate the conclusions of the composition and structure design of LIREC. The results showed that, the infrared emissivity of coatings can significantly decrease when①the flake metallic powder was elected as pigment, and②the high-infrared transparent resin was elected as adhesive, and③the polarity increases after grafting resin adhesive with polar groups, enhances its compatibility with the metallic paint and reduces the gap in the coating, and④the metallic flake pigment was spread out in order in the coating. And the coating with low infrared emissivity (about 0.1) was prepared.Through the preparation of the different attachment rates of Cu flake pigments, infrared coating resin layer thickness can be adjusted, thereby regulating the infrared emissivity of coating. The high attachment rate of the metal pigments can significantly reduce the infrared emissivity of coating. The impact of the infrared transparency of the resin on infrared emissivity of coating reduces significantly when the high attachment rate of Cu flake pigment was elected. Even if the less infrared transparency resin was used, LIREC can be obtained. Therefore, the choice scope of resin adhesive is broadened, and lay a solid foundation for the development of LIREC with good properties.After experimental verification, the infrared emissivity aformula can be used to calculate approximately the infrared emissivity of coating containing flaky particles and can reflect the main factors of the infrared emissivity of the coating.(3) Study of the composition and structure on the mechanical properties of the LIREC:The impacts of polar groups of EPDM-g-MAH, pigment content and resin structure on the mechanical properties of LIREC were analyzed. The results showed that, the mechanical properties of LIREC can be improved by designing the composition and structure of LIREC. 1) Grafting low polarity adhesive with polar groups. The XPS analysis shows that the polar groups of EPDM-g-MAH can form coordination bonds with the metal, significantly improve the mechanical properties of LIREC. 2) Adjusting pigment content. The adhesion of LIREC increased with the increased pigment content, and the hardness first increased and then decreased. The flexibility and resistance to impact strength were significantly reduced for rigid chain of PU-based coatings, while the flexibility and resistance to impact strength of the coating were less affected for the flexible chain resin EPDM-g-MAH. 3) Adjusting resin structure. The flexibility and impact strength resistance of LIREC prepared with EPDM-g-MAH were better than that prepared with polyurethane, while the hardness was somewhat less. The flexibility and impact strength resistance of LIREC prepared with epoxy modified polyurethane were greatly improved, while the adhesion and hardness remain basically unchanged.(4) Study of the composition and structure on the corrosion resistance of LIREC:The corrosion mechanism and process of LIREC was studied in aqueous salt solutions. The results showed that the corrosion failure of LIREC was mainly due to the corrosion of Cu powder paint generating CuCl, causing a substantial increase in infrared emissivity. The resin adhesive can provide protection to the pigments and slow down the corrosion process. Pre-corrosion, anti-seepage properties of the resin play an important role, the better in resin with good resistance to water seepage, the slower the infiltration rate of corrosion solution; at the latter part of corrosion the resin adhesion to metal pigments plays a more important role, the strong adhesion is able to slow down the interface of the sparkling progress. EPDM and polyurethane which were modified as resin adhesive, and LIREC were prepared. The composition and structure of LIREC on corrosion resistance was studied. The results showed that, the corrosion resistance of LIREC can be improved by designing the composition and structure of LIREC. 1) Grafting low polarity adhesive with polar groups. EPDM modified by the MAH increased the polarity, and significantly increased the compatibility and adhesion with metallic pigment, reducing the porosity of the coating and thus enhancing the corrosion resistance of LIREC. 2) Adjusting the composition and structure of resin. Resin adhesive modified by introducing the component with stronger corrosion resistance, and full consideration should be given on the surface tension between the various components. The polyurethane modification to introduce the epoxy which has a stronger adhesion to metal paint can improve corrosion resistance of LIREC. Due to the much difference in surface tension between fluorine composition and epoxy resin, the mixed capacity is poor, so the corrosion resistance of LIREC got worse when the both two were used. 3) Increasing the compactability of coating, and reducing the pores in the coating. The study of Epoxy-modified polyurethane (EPU) showed that proper curing temperature, composition ratio and the type of epoxy resin can improve the degree of crosslinking and reduce the structural pore, and appropriate defoamer usage and curing temperature can reduce the pores caused by the bubbles and solvent evaporation, thereby increasing the corrosion resistance of LIREC. 4) The corrosion resistance of LIREC which prepared with resin adhesive with stronger corrosion resistance is not determinately better. And full consideration should be given on the pigment content needed, the anti-seepage properties of resin adhesive and the adhesion between resin adhesive and metal pigment. 5) Smearing high infrared transparency finish on LIREC. The LIREC was prepared with high infrared transparency EPDM-g-MAH as the finish and EPU-based material, the infrared emissivity of the coating increases 0.05, but the corrosion resistance has substantially increased.(5) Study of the composition and structure on the heat aging and light aging properties of LIREC:The heat aging property of different LIREC was studied. The results showed that the reason for the increased infrared emissivity in thermal aging is oxidation of Cu powder pigment. The resin adhesive can provide protection to the pigments and slow down the oxidation process, and protect performance of resin adhesive with the good compatibility with pigment and the strong adhesion was better. EPDM-g-MAH/20% Cu and EPU/50% Cu coatings had good heat aging properties, and the coatings can be used for a long time below 433 K.The light aging property of different LIREC was studied. The results showed that, with the extension of time of artificial accelerated aging, the loss of light and color and relatively mild powder occurred on low infrared emissivity coating, and the infrared emissivity of coating was also gradually increased. The poor compatibility of binder components could result in two-phase separation, increasing the absorption of ultraviolet light and accelerating the aging; The decrease of the content of components vulnerable to UV-degradation can increase the resistance to artificial accelerated aging of the coating. The order of artificial accelerated aging-resistant properties of low infrared emissivity coatings was: FPU/50% Cu > PU/50% Cu > EPDM-g-MAH/20% Cu > EPU/50% Cu > EPDM-g-MAH@EPU/50% Cu, and was positively correlated with the resistance of artificial accelerated aging of the used adhesives.更多还原