共查询到17条相似文献,搜索用时 781 毫秒
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聚氨酯一聚丙烯酸酯共聚乳液的合成研究 总被引:4,自引:0,他引:4
以甲基丙烯酸β-羟乙酯封端的聚氨酯大分子单体与丙烯酸酯类单体进行乳液共聚,合成了以聚丙烯酸酯(PA)为主链、聚氨酯(PU)为侧链的接枝共聚物(PA-g-PU)乳液,用IR光谱和^1H NMR光谱对该聚氨酯大分子单体及PA-g-PU接枝共聚物进行了表征,并对影响聚氨酯-聚丙烯酸酯共聚合的因素进行了探讨。结果表明:聚氨酯大分子单体的加入对乳液聚合的速率造成较大的影响。该体系的表观活化自由能为99.39KJ/mol,Rp∝[I]^0.87,Rp∝[S]^0.12。 相似文献
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首先采用无皂乳液聚合法合成了表面带负电荷、粒径为360 nm的单分散聚苯乙烯(PSt)乳液,并利用聚乙烯亚胺(PEI)在25℃下对PSt乳胶粒表面进行修饰,得到了表面带有正电荷的PSt种子乳液;然后以乙醇和水的混合物为反应介质,采用种子乳液加入法,使钛酸正丁酯(TBT)在修饰后的乳胶粒表面进行水解与缩合,制备出了核壳结构PSt/TiO2复合微球,利用电镜对复合微球的结构形态进行了表征.结果表明,PSt乳液改性时体系的zeta电位随着PEI用量的增加而升高,当PEI用量为PSt聚合物重量的15%时,体系的zeta电位从原来的-40.3 mV升高到了38.3 mV,达到对PSt乳胶粒表面改性的最佳值;在制备PSt/TiO2复合微球时,TiO2包覆量随着反应时间的延长而增加,反应7 h时达到90.2%的最大值;随介质中水含量的增加,吸附到复合微球表面上的TiO2纳米颗粒逐渐减少,复合微球表面逐渐变得光滑,当EtOH/H2O质量比为100/6.0时,得到结构均一、壳层厚度为29 nm的核壳结构PSt/TiO2复合微球. 相似文献
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有机/无机纳米复合粒子平衡型态的热力学计算 总被引:1,自引:0,他引:1
有机/无机纳米复合粒子是一种应用广泛的复合材料, 采用细乳液聚合方法是制备此类复合粒子的有效途径, 其中分裂/融合过程是一种新型的制备工艺. 纳米复合粒子的型态控制是一个非常重要的方面, 从热力学角度出发, 把界面Gibbs自由能最低这一基本热力学原理应用于计算细乳液聚合、采用新型分裂/融合工艺制备的有机/无机纳米复合粒子平衡型态, 并推导了核壳型、半球型、夹心型和分离型复合粒子平衡型态的热力学方程. 通过比较特定制备条件下不同形态复合粒子的界面Gibbs自由能, 可以预测最稳定的有机/无机纳米复合粒子平衡型态. 相似文献
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首先采用无皂乳液聚合法合成了表面带负电荷、粒径为360nm的单分散聚苯乙烯(PSt)种子乳液,并以EtOH/H2O混合物为分散介质,利用γ-氨丙基三乙氧基硅烷(KH-550)在25℃下对PSt微球表面进行改性,得到了表面硅烷化并带有正电荷的改性PSt种子乳液,然后在碱性条件下加入原硅酸乙酯(TEOS)使其和微球进行共水解与共缩聚,制备出了核壳结构PSt/SiO2复合微球,并利用电镜对复合微球的结构形态进行了表征.研究表明,PSt种子乳液改性时体系的zeta电位随着KH-550用量的增加而升高,当KH-550用量为PSt种子重量的1/3时,体系的zeta电位从原来的-34.5mV升高到了38mV,达到对PSt微球表面改性的最佳值;在制备PSt/SiO2复合微球时,TEOS水解缩聚形成的SiO2包覆到改性微球上的量随着反应时间的延长而增加,反应24h时达到97.9%的最大值;随介质中水含量的增加,吸附到复合微球表面上的SiO2纳米颗粒逐渐减少,复合微球表面逐渐变得光滑,当EtOH/H2O质量比降低到60/28.5时,得到结构均一、壳层厚度为35nm的核壳结构PSt/SiO2复合微球。 相似文献
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探讨了热力学基本原理及判据,以及如何利用吉布斯自由能判断变化的方向和限度;并对Fe/Fe_3O_4纳米磁性材料合成过程中的热力学行为进行了较详细的研究。通过热力学分析,认为可以利用歧化反应及以Fe~(2+)离子作为起始物合成Fe/Fe_3O_4磁性材料。 相似文献
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Xiaolei Zhang Mingwang Pan Shengnan Xing Jingsheng Li 《Frontiers of Chemistry in China》2008,3(1):27-32
An ionomer-type of polyurethane (PU) emulsion was prepared from toluene diisocyanate (TDI), polypropylene glycol (PPG) and
dimethylol propionic acid (DMPA) following a self-emulsification process. The modified poly(vinyl chloride) (PVC) emulsion
resin was obtained by in situ emulsion copolymerization using the PU as seeds in an autoclave. The effects of PU molecular
weight on the mechanical properties and thermal stability of the PU/PVC materials were investigated. The composite latex particles
and composite materials were determined and characterized using a laser particle size analyzer, transmission electron microscopy
or scanning electron microscopy. The study results showed that the PU/PVC hybrid emulsion particles possess a core/shell structure.
When the general mechanical properties of the composite materials increase, the thermal stabilities decrease a little. The
tough fractures on the surface of the PU/PVC composite sample following impact are quite obvious.
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Translated from Journal of Hebei Normal University (Natural Science Edition), 2007, 31(2): 228–232 [译自: 河北师范大学学报(自然科学版)] 相似文献
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Comparative study between core-shell and interpenetrating network structure polyurethane/polyacrylate composite emulsions 总被引:2,自引:0,他引:2
Anionic aqueous polyurethane dispersion was prepared by using carboxyl acid group to make the polyurethane dispersible, and then nanograde core-shell and crosslinked IPN structure polyurethane/polyacrylate composite latex (PUA) were synthesized by soap-free emulsion polymerization method with polyurethane dispersion as seed. FTIR, DSC, dynamic light scattering, TEM, ESCA, TGA, electronic tensile machine were employed to investigate the structures and properties of the composite latex and their polymers. Meanwhile the core-shell composite PUA emulsion and the crosslinked IPN composite PUA emulsion were compared. The results showed that the particle morphology of PUA composite emulsion is inverted core-shell structure with polyacrylate as the core and with polyurethane as the shell. The morphology of the crosslinked PUA emulsion was multi-core structure. The surface in core-shell PUA contains rich PU phase. The phase structure of the crosslinked PUA is more uniform. Three transition temperatures are observed for the core-shell composite PUA, two transitions are observed for the film from the crosslinked PUA. The TGA curves of core-shell PUA and crosslinked PUA exhibit two stages, the first stage corresponds to the thermal decomposition of hard segments in seed polyurethane; the second stage corresponds to the decomposition of soft segments in PUA and decomposition of polyacrylate. With the increase of glycidyl methacrylate (GMA) amounts in PUA composite emulsions, the tensile strength of the PUA films as well as the average diameter of the PUA composite emulsion particles increase, the elongation at break of the PUA films decreases. 相似文献
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C. Vanga Bouanga K. Fatyeyeva P.-Y. Baillif C. Khaokong J.-F. Pilard M. Tabellout 《Macromolecular Symposia》2010,290(1):175-184
Summary: Composite polyurethane/polyaniline (PU/PANI) films have been chemically prepared by oxidative in-situ polymerization of aniline inside the previously swelled PU film. Swelling kinetic studies have shown that for PU films the swelling degree of aniline is 25 wt.%. The dielectric and electrical properties of the composite films were measured using dielectric relaxation spectroscopy and four-probe method. Dielectric measurements as a function of temperature and frequency revealed the presence of a relaxation process for the composite PU/PANI-HCl film. This relaxation was explained in terms of interfacial polarization due to the double-layered structure of the composite film. The activation energy values found by dielectric and electrical measurements are close and this result confirms the conducting character of the PANI containing layer. 相似文献
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Chien‐Yu Li Wen‐Yen Chiu Trong‐Ming Don 《Journal of polymer science. Part A, Polymer chemistry》2007,45(15):3359-3369
The morphology of PU/PMMA hybrid particles prepared by miniemulsion polymerization was predicted through the consideration of their Gibbs free energy changes. Five morphological states of PU/PMMA hybrid particles were proposed and their Gibbs free energy changes were calculated. Before the formation of hybrid particles, the initial state included a monomer mixture of PU prepolymer, MMA, a chain extender, TMP, and an initiator, which was in droplets suspended in water containing SDS. Two assumptions were made. First, the densities of all states were the same. Secondly, secondary nucleation of particles was negligible. Thus the size of initial droplet and final particle was unchanged through miniemulsion polymerization. The interfacial tensions were measured by a pendant drop method and were used for calculation. The preferred morphology of PU/PMMA hybrid particle had the minimum value of ΔGphase. Different NCO/OH ratios of PU and initiators of MMA were used to study the morphological change of PU/PMMA hybrid particles. When BD was used as the chain extender of PU, the hybrid particles showed the PU‐rich phase as the shell and PMMA‐rich as the core. When incorporating bisphenol A into PU polymer, the homogeneous structure of hybrid particle was preferred. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3359–3369, 2007 相似文献
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Yang Yang Zhenxing Jia Ying Wang Yi Gu Jiaqiang Qin 《Colloid and polymer science》2013,291(5):1049-1055
Nonspherical polymer particles have attracted increasing attention recently. In this paper, micron-scale hemispherical polyimide (PI) particles were fabricated using water-soluble poly(amic acid) ammonium salts (PAAS) by a novel inverse emulsion technique. In the process, liquid paraffin was used as a continuous phase, the mixed solution of PAAS and water as a dispersed phase and sorbitan monooleate (Span80) as a surfactant. The research suggested that water as a stabilizing agent played an important role in forming stable emulsion. As the amount of water increased, stability of the emulsion increased gradually and morphology of PI particles transformed from sphere to ellipsoid, and finally to hemisphere. The concentration of PAAS solution and Span80 both affected the shape of particles, which changed from spherical to hemispherical by increasing the PAAS/Span80 concentration. The mechanism of forming hemispherical PI particles was discussed based on interfacial tension and interfacial free energy changes. Via adjusting the composition of the system to change the corresponding interfacial tension, we could get the particles with different morphologies. Furthermore, the change in structure characterized by FT-IR spectroscopy demonstrated that PAAS had been converted to PI after adding the dehydrating agent to the emulsion. And TGA results showed that the obtained PI particles had excellent thermal stability. 相似文献