Thermal and photochemical curing of isocyanate and acrylate functionalized oligomers

Dual-cure formulations have been developed in order to broaden the range of applications of UV-radiation curing and achieve a sufficient cure of the non-illuminated areas of protective coatings, like the shadow areas of three-dimensional substrates or the deep-lying layers of thick pigmented coatings. In complement to the conventional acrylic photopolymerization, such systems involve a polyaddition reaction between isocyanate and hydroxyl functions upon heating, thus imparting satisfying mechanical properties to the coatings, even in the non-irradiated areas. For a quantitative study of the two curing reactions, infrared spectroscopy was chosen because it allows one to monitor accurately the chemical modifications induced in thin films by heat or light. This technique proved particularly useful to follow the polyaddition reaction through the decay of the characteristic IR band of the isocyanate group at 2271 cm⁻¹. Several factors were shown to affect the reaction rate, in particular the chemical structure of the various functionalized compounds, the moisture content in the atmosphere, the curing temperature and the presence of amino catalysts. The viscoelastic properties of the resulting material have been evaluated by dynamic mechanical analysis and shown to be highly dependent on the curing conditions and the type of polymer network formed. For coatings which remain too soft in the dark areas, a thermal initiator was added to promote some further polymerization of the acrylate monomers.     

表面活性单体存在下的MMA／BA乳液共聚合（Ⅱ）：聚合动力？…

研究了表面活性单体「磺化－十二醇－烯丙基甘油－丁二酸酯钠盐（ＺＣ－Ｌ）」的用量对ＭＭＡ／ＢＡ／ＺＣ－Ｌ乳液聚合速率和粒径的影响,用Ｃｏｒｌｔｉｒ ＬＳ２３０型激光粒径分析仪测定聚合过程中乳液的粒径和粒径分布变化,并与ＭＭＡ／ＢＡ无皂乳液聚合及十二烷基苯磺酸钠存在下的ＭＭＡ／ＢＡ乳液聚合作了比较。「ＺＣ－Ｌ」〈ＣＭＣ时,成核机理为均相成核机理,乳胶粒需依靠粒子间的凝聚来提高表面电荷密度而稳定;「ＺＣ     

含环氧基的丙烯酸酯弹性体的合成及其对聚氯乙烯改性研究

以丙烯酸丁酯（ＢＡ），甲基丙烯酸甲酯（ＭＭＡ）和甲基丙烯酸缩水甘油酯（ＧＭＡ）为原料，通过分段乳液聚合，合成了一系列具有不同组成结构的三元共聚物—Ｐ（Ｂ—Ｍ—Ｇ）弹性体，并对此弹性体改性的ＰＶＣ的抗冲击性能进行了系统研究．结果表明：改性剂组成结构的变化对改性体系的冲击性能有较大影响，改性ＰＶＣ的冲击性能最高可达７９ｋＪ／ｍ２．动态力学及ＳＥＭ实验表明，ＰＶＣ与改性体系系部分相容的共混体系，其断裂行为是明显的韧性断裂特征．本文还对改性体系的力学性能进行了研究．     

黄酮/叔胺引发三丙二醇二丙烯酸酯的光聚合反应

采用实时红外光谱(RTIR)研究了黄酮(FL)为紫外光光敏剂, 不同氢给体(如叔胺)为助引发剂时三丙二醇二丙烯酸酯(TPGDA)的光聚合反应. 结果表明, FL分子中的大π共轭体系使其UV吸收峰的摩尔消光系数(ε_max)远远高于商业化光敏剂二苯甲酮(BP). 当FL与不同助引发剂配合使用时, TPGDA光聚合动力学有较大差异, 其中叔胺体系助引发剂能够与激发态FL发生有效的电子/质子转移过程, 产生胺烷基自由基活性种引发TPGDA的光聚合反应, 所得固化膜的最终双键转化率(DC_f)为93%~97%, 接近完全固化; 而芝麻素(SM)及胡椒环(BDO)作为助引发剂时TPGDA的聚合速率则很低, 固化膜的DC_f仅为32%~38%. 当光敏剂质量分数为1.0%, 4-N,N'-二甲氨基苯甲酸乙酯(EDAB)质量分数为1.0%时, FL/EDAB引发TPGDA的聚合动力学与商业化BP/EDAB的相同, 所得固化膜的DC_f均为97%.     

STUDY ON THE FORMATION MECHANISM OF MONODISPERSE PARTICLES IN THE EMULSIFIER-FREE EMULSION POLYMEAIZATION OF METHYL METHACRYLATE AND BUTYL ACRYLATE

The formation mechanism of monodisperse polymer latex particles in the emulsifier-free emulsion polymerizationof methyl methacrylate and butyl acrylate with potassium persulfate as initiator was investigated. A multi-step formationmechanism for the monodisperse polymer particles was proposed. The nucleation mechanism is considered to be thecoagulation of the precursor particles by homogeneous nucleation when the primary particles reach a critical size with highsurface charge density and sufficient stability. It had been proved by a special experiment that the early latex particles formedby the coagulation were stable. The primary particles grow by absorbing monomers and radicals in the polymerization systemand then become colloidally unstable again due to the understandable decrease of particle surface charge density, which leadsto the aggregation of the growing particles and the formation of larger latex pedicles therefrom. Aner the nucleation period,the preferential aggregation of the smaller particles in the propagation process leads to the change of the particles towards auniform size and narrower particle size distribution. The coexistence and competition of homogeneous nucleation,coagulation, propagation and aggregation result in the increase of the polydispersity index (U = D_(43)/D_(10)) in the first Stage,then its decrease in the later stage because of the competition of propagation and aggregation, and the gradual formation ofthe monodisperse particles.     

表面活性单体存在下的MMA/BA乳液共聚合(Ⅱ)聚合动力学及机理

研究了表面活性单体[磺化-十二醇-烯丙基甘油-丁二酸酯钠盐(ZC-L)]的用量对MMA/BA/ZC-L乳液聚合速率和粒径的影响,用CoulterLS230型激光粒径分析仪测定聚合过程中乳液的粒径和粒径分布变化,并与MMA/BA无皂乳液聚合及十二烷基苯磺酸钠存在下的MMA/BA乳液聚合作了比较.[ZC-L]CMC时,成核机理包括均相成核和胶束成核机理,生成的粒子因吸收体系中的表面活性单体而稳定存在.     

磷酸酯改性丙烯酸酯复合乳液的制备及其耐腐蚀性能研究

本实验采用乙二醇甲基丙烯酸酯磷酸酯(HEMAP)作为共聚功能单体,与交联功能单体N-(异丁氧基)甲基丙烯酰胺、丙烯酸、甲基丙烯酸甲酯等在可聚合型表面活性剂作用下通过乳液聚合法合成了磷酸酯改性丙烯酸酯乳液体系.通过粒径分析仪、红外光谱仪、热失重分析仪、电化学工作站、耐盐雾试验机等重点探讨不同含量HEMAP对乳液及涂层的粒...     

Structural Design and Property Characterization of Bi-functional Photorefractive Polymer

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Characterization of UV-cured polyester acrylate films containing acrylate functional polydimethylsiloxane

Acrylate functional polydimethylsiloxane (AF-PDMS) was tested as a reactive additive in UV-curable coating formulations. Pencil hardness, solvent resistance, and gloss of the UV-cured films were measured to study the influence of AF-PDMS content on coating properties. Depth-profile analysis by FTIR-ATR and Raman spectroscopy was also performed to investigate the effect of AF-PDMS on the behavior of film formation during UV curing. The kinetics of photopolymerization were monitored by photo differential scanning calorimetry (photo-DSC). Our results show that AF-PDMS containing coating formulations are very sensitive to oxygen inhibition, so that an inert environment such as nitrogen purging is required to avoid coating defects.     

Synthesis and characterization of poly (n-butyl acrylate)-poly (methyl methacrylate) latex interpenetrating polymer networks by radiation-induced seeded emulsion polymerization

A series of latex interpenetrating polymer networks (LIPNs) were prepared via a two-stage emulsion polymerization of methyl methacrylate (MMA) or mixture of MMA and n-butyl acrylate (n-BA) on crosslinked poly(n-butyl acrylate)(PBA) seed latex using ⁶⁰Co γ-ray radiation. The particles of resultant latex were produced with diameters between 150 and 250 nm. FTIR spectra identified the formation of crosslinked copolymers of PMMA or P(MMA-co-BA). Dynamic light scattering (DLS) showed that with increasing n-BA concentration in second-stage monomers, the particle size of LIPN increased. Transmission electron microscope(TEM) photographs showed that the morphology of resultant acrylate interpenetrating polymer network (IPN) latex varied from the distinct core-shell structure to homogenous particle structure with the increase of n-BA concentration, and the morphology was mainly controlled by the miscibility between crosslinked PBA seed and second-stage copolymers and polarity of P(MMA-co-BA)copolymers. In addition, differential scanning calorimeter (DSC) measurements indicated the existence of reinforced miscibility between PBA seed and P(MMA-co-BA)copolymer in prepared LIPNs.