【作者】 丁晓峰；

【导师】 周树学； 武利民；

【作者基本信息】 复旦大学 ， 材料物理与化学， 2011， 博士

【摘要】 自清洁涂层能够将表面污染物或灰尘颗粒在重力、雨水、风力等外力作用下自动脱落或通过光催化降解而除去,具有节水、节能、环保等优点,近年来受到了广泛的关注。目前,基于不同自清洁原理,已发展了两类自清洁涂层。一类是超疏水(水接触角>150°)自清洁涂层,通过水滴滚动带走灰尘,实现类似于荷叶的自清洁功能。但现有超疏水涂层仍存制备工艺复杂、制备面积小、实际服役时间过短等问题。另一类是基于无机半导体材料光催化分解有机物原理制备的自清洁涂层。在这一类自清洁涂层中,最为典型的是二氧化钛(Ti02)涂层。纯Ti02涂层可通过磁控溅射法、化学气相沉积法、溶胶-凝胶法等方法制备,但这些方法一般都需要高真空或高温处理条件,不适合于大面积制备。本文通过具有光催化活性的Ti02纳米粒子与特殊成膜树脂相结合,在室温条件下大面积制备了超双亲、超疏水等多种纳米复合自清洁涂层,详细考察了涂层的结构与性能,为自清洁涂层的大规模实用化奠定了较好的理论和实验基础。主要研究内容与结果如下：(1)采用酸催化溶胶-凝胶法制备的Si02溶胶与自由基溶液聚合制得的含甲氧基硅基苯丙(SA)齐聚物混合为成膜杂化树脂,氨基硅烷(APS)为固化剂,与Ti02纳米粒子复合,在室温下湿固化得纳米复合涂层,再在阳光辐照或人工加速老化下,通过纳米Ti02粒子对聚合物链段的选择性光解,制备了超双亲自清洁涂层。研究表明,纳米复合涂层中的Ti02纳米粒子含量增加或杂化树脂中SA组分含量减小,涂层在辐照下达到超双亲(分别以水和正已烷为探针液体)所需要的时间缩短。在无机Si02溶胶与有机SA质量比为9：1,Ti02纳米粒子含量为2.0 wt%时,涂层在阳光下辐照10天即可达到超双亲性能,即使Ti02含量减小到0.5 wt%,阳光辐照16天后也能获得超双亲性。SEM观察表明,涂层的超双亲特性是由表面点状微裂纹和暴露的纳米Ti02粒子造成的。另外,力学性能测试发现,涂层在人工加速老化1440小时后仍能保持铅笔硬度高达4H的力学强度。但当SA组分含量高于30 wt%时,光催化降解后涂层表面出现微粉化,力学性能严重劣化。UV-Vis光谱测试表明,涂层老化后透明性有所降低,但1.5 wt%TiO2含量的涂膜仍能保持较高的透明性。亚甲基蓝光催化降解实验表明,所制备的Ti02基超双亲自清洁涂层具有良好的光催化降解有机污染物能力。(2)以双端羟基氟化聚甲基硅氧烷(PMSF)和双端含氢聚二甲基硅氧烷(PDHS)为成膜树脂,将其与纳米Ti02粒子复合,利用Karstedt催化剂在室温下直接制备了聚氟硅氧烷/Ti02纳米复合涂层。FT-IR分析表明,PMSF与PDHS之间发生了脱氢耦合和硅氢加成反应,生成了聚氟硅氧烷成膜基质。SEM和AFM观察发现,当Ti02纳米粒子含量高于25 wt%时,涂层表面出现由纳米Ti02粒子自组装生成的微纳结构,涂层具备有“荷叶”型超疏水性能。当Ti02纳米粒子含量为35wt%时,涂层的水接触角高达168.7±±2.4°,滚动角0.74±0.3°。而且,所制备的超疏水涂层在全pH值(1-14)、-20-200℃温度范围内,或人工加速老化四周后均能保持很好的超疏水性能(WCA>155°)。色拉油污染实验表明,该超疏水涂层在紫外光照射下,能将污染物光催化分解,恢复到原有超疏水状态。冰形成实验及冰附着力测试显示,所制备的超疏水涂层具有较好的防覆冰性能。(3)以三乙氧基硅基封端的PMSF树脂(FPU)和聚甲基苯基硅氧烷(PMBS)为混合成膜树脂,与纳米Ti02粒子复合,采用APS为固化剂,在室温下直接制备了力学性能优异的超疏水涂层。当Ti02纳米粒子用量高于35 wt%时,所制备的涂层表面具有接触角高于150°,滚动角小于10°的“荷叶”型超疏水自清洁性质。SEM和AFM观察显示,超疏水涂层表面存在微纳复合粗糙结构。涂层表面硬度随APS固化剂和Ti02纳米粒子用量的增加先增加后减小,随FPU用量的增加而减小。在Ti02纳米粒子为35-42 wt%、PMBS/FPU质量比9：1、APS用量为20-30 wt%时,所制备的涂层具有较好的力学强度和疏水性能。QUV加速老化840小时后,涂层表面接触角没有发生明显减小,仍能保持超疏水性能,力学强度也没有明显减小。色拉油光催化降解实验表明,所制备的超疏水自清洁涂层具有光催化分解有机污染物能力和自我恢复特性。(4)以有机硅树脂(Dow Corning@ 3037)为成膜树脂,APS为固化剂,与Fe304纳米粒子复合,在室温条件下,一步法制备了含磁性粒子的纳米复合涂层。当Fe304纳米粒子用量超过48 wt%时,涂层表面具有微纳复合粗糙结构。当Fe304纳米粒子用量为48和56 wt%时,涂层表面的水接触角分别为156.4°和158.3°,滚动角分别为6.5°和4.3°,表明所制备的涂层具有“荷叶”型超疏水自清洁性能。人工加速老化960小时后,涂层表面接触角和铅笔硬度没有发生明显的减小现象。所制备的超疏水涂层在10-3000 MHz范围内具有高达60%的电磁屏蔽效能。更多还原

【Abstract】 In recent years, self-cleaning coatings have received great interests because they can remove or decompose the contaminates or dust particles under the gravity, rain, wind, and so on. Until now, two kinds of self-cleaning coatings have been developed according to different self-cleaning principles. One is the self-cleaning superhydrophobic (water contact angle>150°) coatings, which remove the dust through rolling of water droplets, namely, in a way being similar to the "lotus leaf" effect. However, the current methods to fabricate superhydrophobic coatings have many shortcomings, such as, high complexicity, small area, high temperature treatment, expensive apparatus, and etc. The durability of the superhydrophobic is generally poor. Another self-cleaning coatings is prepared based on the photo-decomposition of organic pollutes by inorganic semiconductor materials. TiO2 coating is a typical example of this kind of self-cleaning coatings. Pure TiO2 coatings can be prepared by magnetic sputtering, chemical vapor deposition (CVD), sol-gel, and etc. However, these methods need high vacuum or high temperature conditions, being unsuitable for large-scale preparation. In this study, large-scale fabrication of both supra-amphiphilic and superhydrophobic nanocomposite self-cleaning coatings were conducted at room temperature by combinding TiO2 nanoparticles with special polymer binders. The structure and properties of the coating were studied. The research contents and results are as follows:(1) Supra-amphiphilic nanocomposite coatings were fabricated by mixing titania nanoparticles (Degussa P25) with a sol-gel derived silica sol and methoxysilane group-bearing styrene-co-acrylate (SA) oligomer, and curing with aminopropyltriethoxysilane (APS) at ambient temperature. The amphiphilic, mechanical and optical properties of the nanocomposite coatings with different titania contents and matrix compositions were investigated before and after sun-illumination. Supra-amphiphilic surfaces were achieved just after the coatings were placed in sunshine for a short time. The higher the amount of TiO2 nanoparticles or the lower the fraction of SA copolymer is, the shorter the time to reach super-amphiphilicity is. Accelerated weathering tests showed a good durability especially for the coatings with low fraction of organic phase while photocatalytic activity experiments with methylene blue demonstrated an excellent self-cleaning property of the coatings even with titania content less than 2.0 wt%. The mechanism for the rapid formation of supra-amphiphilic surface with self-cleaning performance was explained.(2) Fluorinated polysiloxane/TiO2 nanocomposite coatings were directly prepared at room temperature using a, co-bis(hydroxylpropyl)-terminated fluorinated polysiloxane oligomer (PMSF) and co-bis(hydrogen)-terminated poly(imethylsiloxane) (PDHS), Karstedt catalyst, and TiO2 nanoparticles. FT-IR spectra analysis shows that dehydrocoupling and hydrosilylation reactions took place between PMSF and PDHS, forming dried fluorinated polysiloxane coatings. SEM and AFM demonstrate that the micro-nano binary structure was formed by TiO2 nanoparticles self-assemble at TiO2 nanoparticle content beyond 25 wt%. Meanwhile, the coating exhibited a water contact angles (WCA) of as high as 168.7±2.4°and a sliding angle (SA) of as low as 0.7±0.3°at 35 wt% of TiO2 nanoparticle content. Moreover, the as-prepared superhydrophobic coatings also display excellent durability at various environmental conditions. For example, they show superhydrophobic properties (WCA>165°) within entire pH range (1-14), after treating at temperature ranging from -20 to 200℃for 30 min, or after accelerated weathering tests for 4 weeks. Salad oil photocatalyis experiment reveals the as-prepared superhydrophobic coatings can decompose pollutes and recover its superhydrophobicity under UV illumination. The as-prepared superhydrophobic coatings have good anti-icing performance.(3) Robust superhydrophobic coatings were directly fabricated at room temperature using triethoxysilyl-terminated PMSF resin (FPU) and poly(methylphenylsilicone) resin (PMBS), APS curing agent, and TiO2 nanoparticles. The coatings have superhydrophobicity (WCA>150°and SA<10°) when the content of TiO2 nanoparticles is more than 35 wt%. SEM and AFM images reveal that the superhydrophobic coatings have micro-nano binary roughness. The pencil hardness and pendulum hardness first increase then decrease with increasing dosage of APS or TiO2 nanoparticle content, and steadily decrease with increasing amount of FPU. The coatings have robust mechanical properties and superhydrophobicity for the those coatings being composed of PMBS/FPU(9:1),35-42 wt% TiO2 nanoparticles and 20-30 wt% APS. The WCA and mechanical strength of the coatings did not show obvious variation even after 840 hours accelerated weathering test. Salad oil photocatalyis experiment reveals the as-prepared superhydrophobic coatings have photocatalytic activity and self-recovery property. (4) Superhydrophobic nanocomposite coatings were readily prepared by mixing of silicone resin (Dow Corning@ 3037), aminopropyltriethoxysilane and FesO4 nanoparticles, and subsequently curing at an ambient temperature. The surface wettability, surface morphology and composition, and long-term durability of the coatings were investigated by water contact angle analysis, filed emission scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and QUV accelerated weathering tests, respectively. WCA of 156.4°and 158.3°, and SA of 6.5°and 4.3°are obtained at 48 and 56 wt% of Fe3O4 content, respectively. The coatings display a pencil hardness of B, excellent weatherability, and electromagnetic shielding effectiveness beyond 60% in the frequency range of 10-3000 MHz.更多还原