【作者】 祁元春；

【导师】 董擎之；

【作者基本信息】 华东理工大学 ， 材料科学与工程， 2014， 博士

【摘要】 紫外光固化技术由于其成型迅速、工艺简单、节约能源、环境友好、适用于规模化工业生产等特点,可以用来制备性能优异的清漆涂膜。在紫外光固化涂料领域中,脂环族聚氨酯丙烯酸酉(Cycloaliphatic polyurethane acrylate, CPUA)低聚物是一种重要的紫外光固化用树脂,它结合了聚氨酯和聚丙烯酸酯的性能优点,具有良好的附着力、柔韧性、耐磨性和耐低温性。另外,CPUA分子中环己基代替了传统涂料中的苯环,提高了紫外光固化涂膜的耐黄变性和耐候性。本论文探讨了四种常见的聚醚型二元醇软段,聚乙二醇1000(PEG1000)聚四氢呋喃醚1000(PTMG1000)、聚丙二醇1000(PPG1000)和聚丙二醇2000(PPG2000)对CPUA紫外光固化涂膜性能的影响,并以性能最佳的CPUA紫外光固化涂膜为基础进行共混改性,制备了脂环族聚氨酯丙烯酸酯/脂环族环氧丙烯酸酯、脂环族聚氨酯丙烯酸酯/脂环族环氧树脂和脂环族聚氨酯丙烯酸酯/脂环族环氧树脂/低分子量的含硅丙烯酸酯KH570紫外光固化共混涂膜,并考察了它们的微观形貌、相结构与涂膜的热稳定性、机械性能及涂膜表面性能之间的关系。另外,对采用自由基/阳离子混杂紫外光固化技术制备的互穿聚合物网络(Interpenetrating Polymer Network, IPN)体系UTC-3的动力学成因和相分离行为进行了深入研究。具体研究内容及主要结论如下：1.以异佛尔酮二异氰酸酯(IPDI)和甲基丙烯酸羟乙酯(HEMA)为硬段,聚醚二元醇PEG1000、PTMG1000、PPG1000、PPG2000为软段,分别制备了四种不同的CPUA紫外光固化涂膜CPUA-1、CPUA-2、CPUA-3和CPUA-4。这四种光固化涂膜的主要性能相差不大,其中,低聚物CPUA-1由于PEG1000分子的链结构规则,结晶性好,涂膜硬度高,但是其较高含量的醚键导致低聚物黏度较大,涂装困难,且涂膜耐清洗性差；而低聚物CPUA-3由于PPG1000分子侧基的存在降低了体系的结晶性,低聚物黏度较小,得到的紫外光固化涂膜各项性能指标良好,比较适合规模化工业生产。通过对聚醚型二元醇的分子结构与相应的紫外光固化CPUA涂膜性能之间关系的分析可知,软段的结构和含量是决定CPUA涂膜性能的重要影响因素：软段越柔软,低聚物越容易结晶,涂膜的硬度和耐热性就越好；软段分子量越大,硬段含量越少,涂膜的硬度越低。2.紫外光固化脂环族聚醚型聚氨酯丙烯酸酯CPUA-3和脂环族环氧丙烯酸酯(Cycloaliphatic epoxy acrylate,CEA)共混改性涂膜中,CPUA-3、CEA和活性稀释剂三羟甲基丙烷三甲基丙烯酸酉(Trimethylolpropane triacrylate, TMPTMA)三者相容性良好,在紫外光固化过程中发生自由基共聚,无明显的相分离现象。由涂膜液氮淬断面的扫描电子显微镜(SEM)图可知,共混涂膜UEAT-2(CPUA-3、CEA和TMPTMA的组成质量比为30：20：50)的断裂面出现较长的断裂带,且断面比较光滑,表明该组成比时的涂膜具有良好的韧性,此时涂膜的铅笔硬度,摆杆硬度,拉伸性能和耐热性各项性能指标最佳,表面光滑无缺陷。3.紫外光固化CPUA-3和脂环族环氧树脂(Cycloaliphatic epoxy resin, CER)共混改性涂膜中,CPUA-3、CER和TMPTMA三者相容性良好。在紫外光固化过程中,CPUA-3和TMPTMA发生自由基共聚反应,聚合速率相对较高；CER发生阳离子光聚合反应,聚合速率相对较低。两种不同的光聚合类型引发微观相分离现象,体系呈现明显的两相结构。当紫外光固化共混涂膜中CER的质量分数在50%-70%范围内时,两相形成IPN结构。在各种组成配比的涂膜中,具有IPN结构的紫外光固化涂膜UTC-3(CPUA-3. TMPTMA和CER的组成质量比为15：15：70)的综合性能最佳,其力学性能,热稳定性和表面性能均较好,这主要是由于IPN体系中两相聚合物之间具有协同效应,分子链之间存在大量的氢键,能促进了两相之间的相容性,表现为动态热机械分析(DMA)曲线呈单峰态势。4.紫外光诱导相分离的自由基/阳离子紫外光固化共混改性体系中,考察了体系固化前共混体系的差示扫描量热(DSC)曲线和相关玻璃化转变温度Tg,黏流温度Tf及热聚合初始温度Ti,建立了共混体系的温变相图。随着CER含量的增加,紫外光固化共混改性体系的相结构经历了“海-岛”结构(Ⅰ)、双连续结构和“海-岛”结构(Ⅱ)三个阶段。由于CPUA与CER之间存在黏度差异,体系主体相发生的相反转的过程是不对称的。以其中性能最佳的紫外光固化IPN涂膜UTC-3为研究对象,采用SEM测试跟踪了UTC-3共混体系随时间变化的相分离演变过程,发现CPUA-3/TMPTMA/CER共混体系的相分离行为受各组分的模量、黏度、光聚合速率等多种因素的影响,相分离过程比较复杂。基于以上对自由基/阳离子紫外光固化诱导相分离过程的分析,建立了三角亚稳相图,并提出自由基/阳离子紫外光固化体系的相分离分为以下几个阶段：开始相分离、自由基紫外光固化聚合主导期、模量控制相分离的自由基/阳离子紫外光固化共同聚合期、阳离子紫外光固化聚合主导期和相分离终止。5.紫外光固化UTC-3和低分子量含硅丙烯酸酯KH570共混改性涂膜中,KH570与共混体系UTC-3存在一定的相容性。当KH570的质量分数低于1.0wt.%o时,四者能够混溶。含单双键的低分子量丙烯酸酯KH570以侧链的形式进入交联网络,降低了交联密度,为光引发剂,未反应的低聚物和活性稀释剂提供了流动空间,提高了自由基／阳离子紫外光固化共混体系的聚合速率和最终转化率。由SEM图可以观察到,KH570的空间位阻效应使得紫外光固化涂膜UTC-3的微观形貌由IPN结构变为含有大量空穴和缝隙的复杂结构。但是,随着KH570含量的增加,分子间氢键作用占主导,涂膜液氮淬断面逐渐变得平滑而致密。与UTC-3紫外光固化涂膜相比,UTC-3/KH570紫外光固化共混涂膜的机械性能有所下降,但断裂伸长率增大,阻尼性能和热稳定性有明显提高,润湿性也有所改善。另外,由原子力显微镜(AFM)图和X-射线光电子能谱(XPS)图可知,UTC-3紫外光固化涂膜表面的KH570的含量远高于KH570添加到体系中的含量,表明KH570在光固化过程中会发生分子迁移现象,其体相密度低于涂膜表面密度。更多还原

【Abstract】 Ultraviolet (UV) curing technology could be used to synthesize high performance vanish coatings because of its rapid prototyping, easy precessing, energy saving, environmental friendly and suitable for large scaled industrial production. In UV-curable coating field, cycloaliphatie polyurethane acrylate (CPUA) oligomer is an important UV-curable resin, which combines advantages of polyurethane and polyacrylate and has good adhesion, flexibility, wear resistance and low temperature resistance. Phenyl group is substituted by cyclohexyl group in its molecule, improving etiolation resistance and weather resistance of its UV-cured film. In this dissertation the effects of four soft segment polyether diols polyethylene glycol1000(PEG1000), polyoxytetramethylene glycol1000(PTMG1000), polypropylene glycol1000(PPG1000), polypropylene glycol2000(PPG2000) on the properties of alicyclic polyurethane acrylate films were discussed, and cycloaliphatic polyurethane acrylate/cycloaliphatic epoxy acrylate(CEA) UV-cured blend films, cycloaliphatic polyurethane acrylate (CPUA)/cycloaliphatic epoxy resin (CER) UV-cured blend films and cycloaliphatic polyurethane acrylate (CPUA)/cycloaliphatic epoxy resin (CER)/small molecular weight silicon-containind acrylate KH570UV-cured blend films were prepared on the basis of polyether cycloaliphatic polyurethane acrylate with the best overall properties, and the relationships between micro-morphologies, phase structures and thermal stabilities, mechanical properties, apparent properties of the UV-cured blend films were investigated. In addition, dynamic genesises and phase separation behaviors of Interpenetrating Polymer Network (IPN) system UTC-3prepared by free-radical/cationic hybrid UV curing technique were carefully analyzed. The main research works and conclusions are as follows:1. Four different cycloaliphatic polyether polyurethane acrylate UV-cured films CPUA-1, CPUA-2, CPUA-3and CPUA-4were prepared by using isophorone diisocyanate (IPDI) and hydroxyethyl methacrylate (HEMA) as hard segments and polyether diols PEG1000, PTMG1000, PPG1000and PPG2000as soft segments, respectively. Most of their properies were not obviously different, in which CPUA-1UV-cured film had better pencil hardness due to the regular chain structure and good crystallinity of PEG1000molecule, while higher viscosity, and poor wash-resistant due to its higher content of ether bonds; UV-cured film CPUA-3showed the best comprehensive properties especially lower viscosity of its oligomer because PPG1000molecule with side methyl groups reduced the crystallinity of UV-cured film, more suitable for large scale industrial production. According to the analyses of relationship between molecular structure of polyether diols and the properties of corresponding polyurethane acrylates UV-cured films, the content and structure of soft segment could be considered as determined important factors:the softer the soft segment, the easier the crystallization, the better the hardness and heat resistance; the greater molecular weight of soft segment, the lower content of hard segment, the poor hardness.2. In cycloaliphatic polyurethane acrylate and cycloaliphatic epoxy acrylate modified blend UV-cured films, CPUA-3, CEA and reactive diluent TMPTMA with excellent compatibility, copolymerized with each other by free-radical mechnism, surffering no obvious phase separation. Scanning Electron Microscope (SEM) pictures showed the cross section of film UEAT-2(the mass ratio of CPUA-3, CEA and TMPTMA is30:20:50), prepared by liquid nitrogen quenching, presented long fault zones, smooth fault surface, indicatng good flexibility of the film. Moreover, the film had the best comprehensive properties with good pencil hardness, pendulum hardness, tensile properties and heat resistance and smooth surface without defects.3. In cycloaliphatic polyurethane acrylate and cycloaliphatic epoxy resin modified blend UV-curable systems, cycloaliphatic urethane acrylate CPUA-3, the alicyclic epoxy resin CER and reactive diluent trimethylolpropane triacrylate (TMPTMA) had good compatibility. During the UV curing process, CPUA-3and TMPTMA reacted via free-radical copolymerization with relatively higher polymerization rate; CER was polymerized via cationic photopolymerization with relatively lower polymerization rate. Two different types of photo-polymerization initiated micro-phase separation, and the system exhibited an obvious two-phase structure. When the weight percentages of CER were in the range from50%to70%, the two phases formed into IPN structures. UV-cured film UTC-3(the mass ratio of CPUA-3, TMPTMA and CER was15:15:70) with IPN structure exhibited the best overall performance, including better mechanical properties, thermal stability and surface properties, because of synergistic effect of the dual-phase polymers. There were a lot of hydrogen bonds between the two cross-linked network polymer molecular chains, leading to good compatibility between the two phases, which was proved by the performance of Dynamic Thermomechanical Analysis (DMA) curve with a single peak situation.4. In the free-radical/cationic modified blend UV-curable systems initiated by photopolymerization-induced phase separation, Differential Scanning Calorimetry (DSC) curves of the unreacted systems, corresponding glass transition temperature Tg, viscous flow temperature Tf and initial polymerization temperature Ti were investigated, and temperature change phase diagram of the blend systems was established. With the increase of CER content, the phase structures went through three stages:sea-islands structure (Ⅰ), bicontinuous structure and sea-islands structure (Ⅱ). Due to the different viscosity of CPUA and CER, the phase transition process was asymmetry. The UV-cured IPN film UTC-3with best properties was considered as the research object and SEM photos was used to track evolution of phase separation process of UTC-3blend system which was changed with time. It was found that the phase separation behavior of CPUA-3/TMPTMA/CER blend system was affected by the modulus, viscosity, curing reaction rates of two phase polymers. Based on the above analysis of the free-radical/cationic UV curing induced phase separation process, a triangle metastable phase diagram was established, and a conclusion was proposed that the phase separation process of free-radical/cationic UV-curable system was divided into several stages:starting phase separation, UV-curable free-radical photo-polymeric dominant period, modulus controlled phase separation period of UV-curable free-radical/cationic co-photopolymerization, UV-curable cationic photo-polymeric dominant period, phase separation termination.5. In UV-curable UTC-3and a small molecule silicon-containing acrylate KH570modified blend UV-curable systems, KH570had certain compatibility with UTC-3modified system. When mass percentage of KH570is less than1.0wt.%o, four components could be miscible with each other. The introduction of additive KH570with single double bond decreased the density of cross-linked networks, provided flowing space for photo-initiators, oligomers and unreacted monomers, accelerated the polymerization rate of free-radical/cationic hybrid curing systems, and increased the final conversions. As observed in SEM images, microstructure of UV-cured IPN film became complicated structures containing a large number of holes and gaps, which was attributed to the steric effect of KH570. However, with the increase of the content of KH570, hydrogen bond effect between molecules was dominant, and the cross section become smooth and contact. Compared with the UTC-3UV-cured film, the mechanical properties of UTC-3/KH570blend UV-cured systems were decreased, while breaking elongation was increased, damping properties and thermal stability has obviously been improved, wetting resistance was also improved. Furthermore, as shown in the Atomic Force Microscope (AFM) images and X-ray Photoelectron Spectroscopy (XPS) spectra, the content of KH570on the surface of UTC-3UV-cured film was much higher than the addition ratio to the unreactive systems, indicating that the migration phenomenon during photopolymerization process, and the bulk density was lower than the density of UV-cured film surface.更多还原