未改性SiO_2溶胶/聚丙烯酸酯复合乳胶粒的制备及其机理的研究
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摘要
本文采用未经改性的二氧化硅水溶胶,在硅溶胶与聚合物静电相斥的情况下,通过简单的单体滴加聚合工艺制备了硅溶胶／聚丙烯酸酯复合乳液。系统的研究了具有不同物理性能的丙烯酸酯单体的比例对复合乳胶粒结构及复合乳液稳定性的影响,发现随着混合单体中甲基丙烯酸甲酯与丙烯酸丁酯的质量比例(MMA:BA)降低,无机-有机两相结合程度增大,当单体比例降到1：2时,可以形成硅溶胶粒子包裹丙烯酸酯聚合物的草莓型核壳结构复合乳胶粒。增大Si02的用量可以明显降低复合乳胶粒粒径,降低无皂乳液聚合的聚合反应速率,并且提高乳液稳定性。
实验发现单体滴加工艺聚合的规律与传统的Pickering乳液聚合规律相反,因此深入讨论了无机-有机两相的结合机理。在研究了聚合过程粒径分布的基础上提出了无机-有机两相在静电相斥的情况下形成复合乳胶粒的机理,即在聚合反应初期,丙烯酸酯单体按照均相成核机理形成了初始聚合物微粒,由于自身的不稳定,初始微粒在高界面能的推动下与硅溶胶粒子发生吸附,继续聚合增长形成复合乳胶粒。
通过对复合乳液涂膜的结构表征发现涂膜表层存在多孔结构,研究了乳胶粒粒径对涂膜孔结构的影响并讨论了成孔机理。对比了有皂乳液涂与无皂乳液涂膜的吸水率,发现采用无皂乳液聚合技术合成的乳液涂膜吸水率明显降低。随着Si02含量的提高,涂膜硬度提高,但抗冲击性、柔韧性并没有明显的降低,说明本试验工艺可以将纳米硅溶胶粒子均匀的分散在聚合物涂层之中。
Silica sol/Polyacrylate composite latex was prepared through simple drop wise polymerization process under the condition of electrostatic repulsion between negative surface charge of silica and negatively charged polymer particle (derived from the anionic initiator KPS) without any surface modification. The influence of acrylate monomer ratio (MMA:BA) on structure of composite emulsion particles and stability of composite latex has been studied. The results indicated that the encapsulation of silica sol by polyacrylate increased with the monomer ratio (MMA:BA) decreased. The composite particle with core-shell structure can be synthesized when monomer ratio (MMA:BA) is 1:2, which silica particles served as shell and polyacrylate served as core. With the increase of amount of SiO2, polymerization rate and composite particle size had decrease trend. Also, the stability of composite emulsion was significantly improved due to the addition of silica sol.
Based on experiment, it was found that the experimental law of drop wise processes was different from that of Pickering polymerization processes. Through the research on particle size distribution of polymerization process, a composite mechanism was proposed, that precursor particles of polyacrylate, which are formed in the early stage of soap-free emulsion polymerization, are very unstable, so they tend to be absorbed on colloidal silica particles to lower interfacial energy, thus forming composite particles.
The structure of composite film was characterized by Scanning electron microscope (SEM). The images indicated that porous structure existed. Based on the discussion on the influence of composite particle size on porous structure, the mechanism of hollow formation was proposed. Water absorption of coating film of emulsion polymerization with emulsifier and emulsifier-free emulsion polymerization was studied and the result shows that water resistant property of coating film had obviously progress when there wasn't any low-molecular-weight emulsifier involved. With the increase of silica amount, the hardness of coating film enhanced, but shock resistant and flexibility maintain a high-level, which is likely duo to the well-dispersed of silica particles in polymer matrix.
实验发现单体滴加工艺聚合的规律与传统的Pickering乳液聚合规律相反,因此深入讨论了无机-有机两相的结合机理。在研究了聚合过程粒径分布的基础上提出了无机-有机两相在静电相斥的情况下形成复合乳胶粒的机理,即在聚合反应初期,丙烯酸酯单体按照均相成核机理形成了初始聚合物微粒,由于自身的不稳定,初始微粒在高界面能的推动下与硅溶胶粒子发生吸附,继续聚合增长形成复合乳胶粒。
通过对复合乳液涂膜的结构表征发现涂膜表层存在多孔结构,研究了乳胶粒粒径对涂膜孔结构的影响并讨论了成孔机理。对比了有皂乳液涂与无皂乳液涂膜的吸水率,发现采用无皂乳液聚合技术合成的乳液涂膜吸水率明显降低。随着Si02含量的提高,涂膜硬度提高,但抗冲击性、柔韧性并没有明显的降低,说明本试验工艺可以将纳米硅溶胶粒子均匀的分散在聚合物涂层之中。
Silica sol/Polyacrylate composite latex was prepared through simple drop wise polymerization process under the condition of electrostatic repulsion between negative surface charge of silica and negatively charged polymer particle (derived from the anionic initiator KPS) without any surface modification. The influence of acrylate monomer ratio (MMA:BA) on structure of composite emulsion particles and stability of composite latex has been studied. The results indicated that the encapsulation of silica sol by polyacrylate increased with the monomer ratio (MMA:BA) decreased. The composite particle with core-shell structure can be synthesized when monomer ratio (MMA:BA) is 1:2, which silica particles served as shell and polyacrylate served as core. With the increase of amount of SiO2, polymerization rate and composite particle size had decrease trend. Also, the stability of composite emulsion was significantly improved due to the addition of silica sol.
Based on experiment, it was found that the experimental law of drop wise processes was different from that of Pickering polymerization processes. Through the research on particle size distribution of polymerization process, a composite mechanism was proposed, that precursor particles of polyacrylate, which are formed in the early stage of soap-free emulsion polymerization, are very unstable, so they tend to be absorbed on colloidal silica particles to lower interfacial energy, thus forming composite particles.
The structure of composite film was characterized by Scanning electron microscope (SEM). The images indicated that porous structure existed. Based on the discussion on the influence of composite particle size on porous structure, the mechanism of hollow formation was proposed. Water absorption of coating film of emulsion polymerization with emulsifier and emulsifier-free emulsion polymerization was studied and the result shows that water resistant property of coating film had obviously progress when there wasn't any low-molecular-weight emulsifier involved. With the increase of silica amount, the hardness of coating film enhanced, but shock resistant and flexibility maintain a high-level, which is likely duo to the well-dispersed of silica particles in polymer matrix.
引文
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[2]Southeng Wu. Phase structure and adhesion in polymer blends a criterion for rubber toughening[J]. Polymer,1985 (25):1885-1895
[3]童听.乳液法制备有机／无机纳米复合材料的研究[D].沈阳：东北_大学,2001
[4]应建波.核壳结构ACR及其纳米复合材料[D].杭州：浙江工业大学,2004
[5]Valter Castelvetro, Cinzia De Vita. Nanostructured hybrid materials from aqueous polymer dispersions[J]. Advances in Colloid and Interface Science,2004,108-109
[6]Guido Kickelbick. Concepts for the incorporation of inorganic building blocks into organic polymer on a nanoscale[J]. Progress in Polymer Science,2003,28:83-114
[7]龙复,王玮.无机—有机复合高分子乳液研究的进展[J].化工进展,1991(4)：11-14
[8]成国祥,盛京,沈宁祥,姚康德.核-壳型聚丙烯酸酯复合乳液[J].高分子通报,1989(4)：11～17
[9]二宫善吾.乳液聚合法制备有机-无机高分子复合材料[J].精细化学品,1986,20(15)：5-9
[10]龙复,李同年,张卫红.有机-无机复合乳液研究(I)[J].现代涂料与涂装,1996,2：2-3
[11]Takafumi Yokoyama, Yutaka Sugawa. Preparation of monodispersed polymer-modified silica particles radical polymerization using colloid and introduction of functional groups on the composite surface[J]. Polymer Bulletin,1992,28:663-668
[12]F. Corcos, C. Novat. Poly(styrene-b-ethylene oxide) copolymers as stabilizer for the synthesis of silica-polystyrene core-shell particle[J]. Colloid Polymer Science,1999, 500(277):1142-1151
[13]邬润德,童莜莉.聚丙烯酸酯原位乳液聚合包覆纳米硅溶胶的研究[J].有机硅材料,2002,16(4)：1-4
[14]李敬玮,夏宇正.原位水解法聚丙烯酸酯／纳米二氧化硅复合乳液的性能研究[J].胶体与聚合物,2002,20(4)：24～27
[15]Xiqiao Feng, Wolf. Dieter Hergeth, Uwe-Jens Steinau. Polymerization in the presence of seeds. Part Ⅳ:Emulsion polymers containing inorganic filler particles[J]. Polymer,1989, 30:254～258
[16]Wolf.Dieter Hergeth, Peter Starre. Polymerization in the presence of seeds:3.Emulsion polymerization of vinyl acetate in the presence of quartz powder[J]. Polymer,1988,29: 1323～1328
[17]高敬民,方冉.纳米二氧化硅胶体改性核壳型苯丙乳液的合成及性能研究[J].中国涂料,2004,4：1-3
[18]张径,杨玉昆.以SiO2纳米粒子为种子的甲基丙烯酸甲酯乳液聚合[J].化学与粘合剂,2001,4(1)：1-3
[19]张径,杨玉昆.在无机SiO2纳米粒子存在下的苯丙乳液共聚合[J].高等学校化学学报,2002,23(3)：481-485
[20]王国建.有机硅氧烷／丙烯酸酯乳液的无皂共聚合研究[J].建筑材料学报,2002,4(3)：269-273
[21]方荣利,王林.高性能无皂硅丙乳液合成的研究[J].涂料工业,2006,24(7)：29-33
[22]Wolf.Dieter Hergeth, Uwe-Jens Steinau. Polymerization in the presence of seeds, PartIV: Emulsion Polymers containing inorganic filler particle[J]. Polymer,1989,30:254-258
[23]M.J.Percy, C.Barthet. Synthesis and characterization of vinyl polymer-silica colloid nanocomposites[J]. Langmuir,2000,16:6913-6920
[24]M.J.Percy, J.L.Amalvy. Synthesis of vinyl polymer-silica colloidal nanocomposites prepared using commercial alcoholic silica[J]. Langmuir,2004,20:2184-2190
[25]钱翼清,范牛奔.烷基化纳米SiO2/MMA核壳无皂乳液聚合、产物表征及其应用[J].高分子材料科学与工程,2002,18(4)：6-11
[26]Jose-Luiz Luna-Xavier, Alain Guyot. Synthesis and Characterization of Silica/Poly(Methyl Methacrylate) Nanocomposite Latex Particles Emulsion Polymerization Using a Cationic Azo Initiator[J]. Journal of Colloid and Interface Science,2002,250:82-92
[27]Jeongwoo Lee, Chang Kook Hong, Soonja Choe. Synthesis of polystyrene/silica composite particles by soap-free emulsion polymerization using positively charged colloidal silica[J]. Journal of Colloid and Interface Science,2007,310:112-120
[28]Franca Tiarks, Katharina Landfester. Silica nanoparticles as surfactants and fillers for latexs made by miniemulsion polymerization[J]. Langmuir,2001,17:5775-5784
[29]李远,陈建国,陈腊琼.PP／纳米CaCO3分散体系的研究[J].塑料工业,2001,29(1)：16-17
[30]贺鹏,赵安赤.纳米粒子改性高密度聚乙烯的耐磨性研究[J].塑料工业,2001,3(1)：39-43
[31]张金柱,汪信,陆路德.HIPS/TiO2/TAS纳米复合材料的制备及性能[J].中国塑料,2001,15(1)：24-26
[32]宁科功.固体粒子的形貌控制及其在稳定乳液中的应用[D].陕西西安：西安科技大学,2008
[33]毕延莉,张宏伟,刘温霞.水滑石-膨润土异凝聚体的形成及对石蜡乳化效果的初步研究[J].造纸科学与技术,2007,26(4)：22-25
[34]杨礼礼.纳米SiO2／表面活性剂相互作用研究[D].江苏无锡：江南大学,2008
[35]蓝强.表面活性物质与纳米颗粒协同稳定的Pickering乳液[D].山东济南：山东大学,2007
[36]贺拥军,齐随涛,赵世永.纳米粒子稳定乳液及其在纳米结构合成中的应用[J].化学进展,2007,19(9)：1443-1448
[37]Xiaomei Song, Guannan Yen, Yongliang Zhao. Effect of an Anionic Monomer on the Pickering Emulsion Polymerization Stabilized by Titania Hydrosol[J]. Journal of Polymer Science, Part A:Polymer Chemistry,2009,47(21):5728-5736
[38]李煜,王朝阳,陈云华.Pickering乳液聚合制备核-壳结构PS-Si02复合微球[J].功能高分子学报,2009,22(2)：154-158
[39]乌兰.硅溶胶的应用研究[M].西北民族学院学报(自然科学报),2002,23(6)：19-20
[40]李岗,吉静.高硅溶胶含量复合乳液的研究[J].新型建筑材料,2007,4：6-8
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