【作者】 叶超贤；

【导师】 曾幸荣；

【作者基本信息】 华南理工大学 ， 材料学， 2014， 博士

【摘要】 聚丙烯酸酯乳液具有无污染、成本低、成膜性能好等优点，其乳胶膜的耐候性、柔韧性、附着力等性能优良，在建筑、汽车、包装、印刷等领域得到了较为广泛的应用，但乳胶膜的耐热性、硬度等较差，在一定程度上限制其应用。采用无机纳米二氧化钛改性聚丙烯酸酯乳液，制备有机无机纳米复合乳液，可以显著提高乳胶膜的硬度、耐热性、冲击强度等性能，从而进一步扩大其使用范围。然而，由于纳米二氧化钛的比表面积大、表面能高，处于非热力学稳定态，所制备的复合乳液易存在纳米粒子团聚、复合乳液储存稳定性差、制备工艺复杂等缺点。本工作采取两条技术路线，原位制备了聚丙烯酸酯/纳米二氧化钛复合乳液，探讨了制备过程中的影响因素，通过红外光谱（FT-IR）、激光纳米粒度仪（DLS）、X射线衍射（XRD）、透射电镜（TEM）等手段对纳米二氧化钛和复合乳液的结构进行表征，对乳胶膜的热性能、力学性能、紫外吸收性能等进行研究，并分析了复合乳胶粒子的形成机理。论文的研究内容和主要成果包括如下四点：（1）采用溶胶-凝胶法，以钛酸丁酯（TBOT）为前驱体，盐酸（HCl）为催化剂，γ-甲基丙烯酰氧基丙基三甲氧基硅烷（KH-570）为改性剂，制备了KH-570改性纳米二氧化钛溶胶，然后加入MMA、BA、AA等丙烯酸酯单体并进行预乳化，通过原位乳液聚合制备了具有良好稳定性的聚丙烯酸酯/纳米二氧化钛复合乳液。利用FT-IR、XRD、DLS、TEM等手段对改性纳米二氧化钛和复合乳液及乳胶膜进行了表征。改性纳米二氧化钛的晶型为锐钛型，随着盐酸用量的增加，其晶型不变，但晶化度提高。与未改性纳米二氧化钛相比，改性纳米二氧化钛的平均粒径减小且分布变窄。当HCl与TBOT的摩尔比n(HCl)/n(TBOT)为0.48时，KH-570改性纳米二氧化钛的平均粒径最小且粒径分布最窄。改性纳米二氧化钛与聚丙烯酸酯有良好的相容性。适量改性纳米二氧化钛的加入，可以改善复合乳胶膜的冲击性能、硬度和耐热性，但对附着力和弯曲性能影响不大。（2）以甲基丙烯酸甲酯（MMA）为油相，十六烷基三甲基溴化铵（CTAB）和丙烯酸（AA）分别为乳化剂和助乳化剂，加入适量的水，制备了CTAB/AA/MMA/H2O反相微乳液体系。以该体系中的反相胶束为纳米反应器，以TBOT为前驱体，KH-570为改性剂，制备了KH-570改性纳米二氧化钛溶胶。绘制了体系的拟三元相图，研究了影响纳米二氧化钛生成率的主要因素，利用FT-IR、TEM等对KH-570改性二氧化钛进行了表征。当CTAB与AA的质量比为2/3时，所形成的反相微乳液区域最大。随着CTAB与AA的质量比m(CTAB)/m(AA)以及CTAB和AA占油相质量比m(CTAB+AA)/m(MMA)的增大，增容水量相应增大，适宜的m(CTAB)/m(AA)和m(CTAB+AA)/m(MMA)分别为2/3和5/5，而温度对增容水量的影响较小。当增容水量和KH-570与钛酸丁酯质量比分别为44.5%和0.6，反应时间和反应温度分别为20h和25℃时，二氧化钛的生成率为74.9%。KH-570改性纳米二氧化钛的平均粒径在10nm左右，与未改性纳米二氧化钛相比，其亲油性得到了明显改善。此外，在纳米二氧化钛的制备过程中，不需使用乙醇作为分散介质，因此便于后续乳液聚合的稳定进行。（3）在由反相微乳液法制备KH-570改性纳米二氧化钛溶胶中，加入适量的水，使体系从W/O型转变为O/W型，然后通过原位乳液聚合法，合成出聚丙烯酸酯/纳米二氧化钛复合乳液，研究了聚合方法和反应温度以及过硫酸钾（KPS）、TBOT、KH-570、微乳液增容水等用量等对单体转化率、凝胶率、粒径、Zeta电位等的影响。结果发现，适宜的乳液聚合工艺为间歇法。当反应温度为75℃、KPS用量为0.5%、KH-570与TBOT质量比为0.6、TBOT用量为5%、微乳液增容水量为44.5%时，聚丙烯酸酯/纳米二氧化钛复合乳液具有低凝胶率以及良好的反应稳定性和储存稳定性。（4）采用FT-IR、热重（TG）、TEM等对反相微乳液法-原位聚合法制备的复合乳液和乳胶膜的结构进行了表征，对乳胶膜的热性能、力学性能、紫外吸收性能等进行了研究，并探讨了聚丙烯酸酯/纳米二氧化钛复合乳胶粒子的形成机理。结果表明，聚丙烯酸酯/纳米二氧化钛复合乳胶粒呈明显的核壳结构，其中纳米TiO2为核、聚丙烯酸酯为壳，粒径在100～150nm之间。KH-570改性纳米二氧化钛在聚丙烯酸酯中具有良好的相容性和分散性。通过引入纳米二氧化钛，可在一定程度上提高聚丙烯酸酯乳胶膜的耐热性、硬度和冲击强度。当TBOT用量为9%时，复合乳胶膜的最大热失重速率温度、铅笔硬度和冲击强度分别为406.3℃、2H和43kg.cm，高于纯聚丙烯酸酯乳胶膜的397.4℃、1H和39kg.cm。与纯聚丙烯酸酯乳胶膜相比，聚丙烯酸酯/纳米二氧化钛复合乳胶膜对紫外光的吸收强度明显增大，并且随着TBOT用量的增加，复合乳胶膜的吸收强度随之增加。当TBOT用量为9%时，复合乳胶膜的最大吸收波长和吸光度从纯聚丙烯酸酯的298nm和0.40分别增大至314nm和1.75。更多还原

【Abstract】 In the past decades, polyacrylate emulsions have been widely used in buildings,automobile, packaging, printing, etc, which are due to non-pollution, low cost, goodperformance including film-forming ability, weather-resistance, flexibility and adherence.However, the heat-resistance and hardness of the polyacrylate latex films were poor, whichlimited the application at a certain degree. With the introduction of nano-titanium dioxide(TiO2) in polyacrylate emulsion, the polyacrylate/nano-titanlum dioxide composite emulsionscan be prepared, the heat-resistance and hardness of latex film would be improved obviously,and the application can be broadened. Nevertheless, because of the large specific surface areaand high surface energy, nano-TiO2was non-thermodynamic stable state, and the preparedcomposite emulsions had some disadvantages such as agglomeration of nanoparticles, poorstorage stability and complicated preparation technology. In this work, two technology routeswere used to prepared in-situ polyacrylate/n-TiO2composite emulsions, the important effectfactors on preparation process were discussed, the structure of nano-TiO2and compositeemulsions was characterized by Fourier transform infrared spectroscopy (FT-IR), dynamiclight scatting (DLS), X-ray diffraction (XRD) and transmission electron microscopy (TEM),the heat-resistance, mechanical properties and UV absorption property of the latex films werestudied, and the formation mechanism of the composite latex particles was discussed. Themain research contents and achievements are listed as follows:Firstly, KH-570modified nano-TiO2sol was prepared by sol-gel method with tetrabutyltitanate (TBOT) as precursor, hydrochloric acid (HCl) as catalytic agent and KH-570asmodifier, and subsequently polyacrylate/n-TiO2composite emulsions with good stability weresynthesized by in-situ emulsion polymerization method with MMA, BA and AA as reactivemonomers. The modified nano-TiO2, composite emulsion and latex film were characterizedby FT-IR, XRD, DLS and TEM. The results showed that the crystal form of modifiednano-TiO2was anatase. With the increase of HCl amount, the crystal form was unchangeable,but the crystallization degree increased. In contrast to unmodified nano-TiO2, the averagediameter of the modified nano-TiO2decreased and its distribution became narrow. When themolar ratio of HCl to TBOT was0.48, the average diameter of the modified nano-TiO2wasthe smallest and the distribution was the narrowest. KH-570modified nano-TiO2andpolyacrylate had good compatibility. With the addition of appropriate amount modifiednano-TiO2, the impact strength, hardness and heat-resistance of the latex films were improved,but the adherence and flexibility was almost unaffected. Secondly, cetyl trimethyl ammonium bromide (CTAB)/acrylic acid (AA)/methylmethacrylate (MMA)/H2O reverse microemulsions were firstly prepared with MMA as oilphase, CTAB and AA as surfactant and co-surfactant, respectively, and appropriate amountwater. In the reverse micelle used as nanoreactor, KH-570modified nano-TiO2sol wasprepared with TBOT and KH-570as precursor and modifier, respectively. The pseudo-ternaryphase diagram was drawn, the important effect factor on the production rate of nano-TiO2solwas studied, and KH-570modified nano-TiO2was characterized by FT-IR, TEM, etc. Theresults showed that when the mass ratio of CTAB to AA was2/3, the bigger reversemicroemulsion area could be obtained. With the increase of m(CTAB)/m(AA) andm(CTAB+AA)/m(MMA), the solubilizing water amount increased, the appropriatem(CTAB)/m(AA) and m(CTAB+AA)/m(MMA) were2/3and5/5, respectively. Thesolubilizing water amount was affected little by temperature. When solubilizing water amountand the mass ratio of KH-570to TBOT were44.5%and0.6, reaction time and temperaturewere20h and25oC, respectively, the production rate of nnao-TiO2attained74.9%. Theaverage diameter of KH-570modified nano-TiO2was about10nm, and their hydrophobicitywas improved obviously. In addition, in the preparation process of nano-TiO2, ethanol was notadded, which was propitious to the stability of the follow-up emulsion polymerization.Thirdly, in KH-570modified nano-TiO2prepared by reverse microemulsion, theappropriate amount water was added dropwise and the nano-TiO2system changed from W/Omicroemulsion to O/W pre-emulsion. Subsequently, polyacrylate/n-TiO2composite emulsionswere synthesized by in-situ emulsion method. The effect of polymerization method, reactiontemperature, KPS amount, TBOT amount, KH-570amount and solubilizing water amount onthe monomer conversion rate, gel ratio, diameter and Zeta potential was studied. The resultsshowed that batch method was more suitable than seeded semi-continuous method andcontinuous method. When reaction temperature was75oC, KPS amount was5%, the massratio of KH-570to TBOT was0.6, TBOT amount was5%and the solubilizing water amountwas44.5%, polyacrylate/n-TiO2composite emulsion had low gel ratio, high reaction stabilityand storage stability.Finally, the structure of polyacrylate/n-TiO2composite emulsions and latex filmsprepared by reverse microemulsion method and in-situ emulsion polymerization method werecharacterized by FT-IR, TG and TEM, the heat resistance, mechanical properties and UVabsorption property of the latex film were studied. In addition, the formation mechanism ofthe composite latex particles was also discussed. The results showed that thepolyacrylate/n-TiO2latex particles appeared apparent core-shell structure, in which nano-TiO2 and polyacrylate were core and shell, respectively, and the particle size was about100~150nm. KH-570modified nano-TiO2had good compatibility and dispersity in polyacrylate. Theheat resistance, hardness and impact strength of the composite latex films were improved withthe addition of nano-TiO2. When TBOT amount was9%, the maximum weight loss ratetemperature of the composite latex film were406.3oC, and the pencil hardness and impactstrength were2H and43kg cm, respectively, and the maximum weight loss rate temperature,pencil hardness and impact strength of the pure polyacrylate latex film were397.4oC,1Hand39kg cm, respectively. In contrast with the pure polyacrylate latex film, the UVabsorption intensity of the composite latex film increased obviously, and with the increase ofTBOT amount, the UV absorption intensity increased accordingly. When TBOT amount was9%, the maximum absorption wavelength and absorbance of the composite latex film were314nm and1.75, and that of pure polyacrylate latex film were298nm and0.40.更多还原