【作者】 冯金辉；

【导师】 范宏；

【作者基本信息】 浙江大学 ， 化学工程， 2007， 硕士

【摘要】 本文设计并合成了一种带有缩水甘油醚基和聚醚柔性链段的长链型硅烷偶联剂并利用这种长链硅烷偶联剂对硅溶胶中的纳米SiO₂进行表面改性，而后将其添加到环氧树脂中以达到补强增韧的效果。考察了偶联剂种类与用量对纳米SiO₂表面改性效果的影响，包括改性后纳米SiO₂／异丙醇分散体系的流变行为、纳米SiO₂在有机环氧树脂体系中分散性以及对环氧树脂胶粘剂的补强增韧效果。新型长链硅烷偶联剂—缩水甘油醚基聚环氧丙醚三乙氧基硅烷的合成分为两步：首先将烯丙基聚环氧丙醚（APP）与环氧氯丙烷开环生成烯丙基氯醇醚，然后与氢氧化钠闭环，生成带有缩水甘油醚基团封端的烯丙基聚环氧丙醚（GPP）；其次在氯铂酸的催化下，与三乙氧基硅烷通过硅氢加成反应得到缩水甘油醚基聚环氧丙醚三乙氧基硅烷（GPPTES）。采用红外光谱（IR）与核磁共振氢谱（¹H NMR）、化学滴定（环氧值测定、碘值测定）等方法对硅烷偶联剂的结构进行了表征，考察了反应温度、催化剂、时间、聚醚分子量等对反应转化率的影响，得到了最佳的反应条件。采用共沸蒸馏的方法使纳米SiO₂粒子由水相转入异丙醇相中，形成纳米SiO₂的异丙醇分散液，然后分别采用KH560和自制的长链硅烷偶联剂GPPTES4、GPPTES6、GPPTES10和GPPTES17对纳米SiO₂粒子进行表面改性，使得原生的亲水性SiO₂粒子具有一定的亲油性。通过红外光谱（IR）和热重（TGA）分析证实了纳米SiO₂表面接枝了一定量的硅烷偶联剂。透射电镜（TEM）和粒径分析（DLS）结果表明改性的SiO₂粒子以10～20nm的粒径均匀地分散在异丙醇中。采用羟基滴定法考察了偶联剂种类和用量对SiO₂表面活性羟基含量的影响。结果表明SiO₂的表面活性羟基含量随着长链偶联剂用量的增大而逐渐减少，当偶联剂用量增加到25％以后，表面活性羟基数基本保持稳定。在相同用量（mol比）下，发现随着偶联剂分子量的增加SiO₂粒子的表面活性羟基含量逐渐减小，说明除了与表面羟基的化学反应以外，长链偶联剂还具有对活性羟基物理包覆的作用。考察了纳米SiO₂／异丙醇分散液体系的流变性能，发现将纳米SiO₂改性之后，出现了明显的剪切变稀的现象。随着偶联剂分子量的增加，剪切变稀的现象更为明显；而随着偶联剂用量的增加剪切变稀现象首先趋于明显而后逐渐稳定。表明纳米SiO₂表面接枝分子链长的的增加和表面接枝分子数的增加对体系的流变特性有着重要的影响，并且与TGA的结果共同表明，偶联剂的接枝有着饱和值，达到饱和以后，更多的偶联剂不能接枝到粒子的表面。将改性SiO₂的异丙醇分散液加入到环氧树脂的丙酮溶液中，减压除去溶剂后得到纳米SiO₂改性的环氧树脂胶粘剂，进行超薄切片并通过透射电镜（TEM）观察，发现小分子偶联剂（KH560）改性的纳米SiO₂以100nm左右的团聚体存在于胶粘剂基体中，而用自制的GPPTES改性后的纳米SiO₂则以10～20nm的粒径均匀分散于胶粘剂基体中，并且在1～5％的范围内，均能得到良好的分散。考察了纳米SiO₂对环氧树脂胶粘剂的拉伸剪切强度和不均匀扯离强度的影响，发现含有偶联剂处理过的SiO₂的胶粘剂样品的拉伸剪切强度和不均匀扯离强度均比纯树脂要高，而添加未改性的纳米SiO₂性能反而下降。并且随着链长的增加（从KH560到GPPTES4到GPPTES17），拉伸剪切强度和不均匀扯离强度均增加。在1～5％的范围内，拉伸剪切强度随SiO₂添加量的增加有最佳值（2％），而不均匀扯离强度则先迅速增加（小于2％）而后缓慢上升（大于2％）。更多还原

【Abstract】 In this study, a series of novel long-chain silane coupling agent (SCA), containing a terminal glycidol ether group and polyether segment, was synthesized and employed as a modifier for silica particles in the aqueous sol. The modified silica particles were then added into the epoxy resin, the influences of different SCA and their amount on the surface modification of silica particles was investigated, including the rheological behavior of the silica/isopropanol sol, the dispersion of silica particles in epoxy matrix, and the strengthening and toughening effect of the modified silica particles on epoxy adhesives.The synthesis of the novel SCA involved two steps: the epoxidation of the allyl polyether (APP) with epichlorohydrin and sodium hydroxide, and hydrosilation of epoxidated APP with triethyoxyl silane. The structure of the product and the influences of catalyst, reaction time, temperature and molecular weight of APP on the reaction conversion were analyzed by infrared spectrometry, ~1H NMR and chemical titration (titration of epoxide value and iodine value), and the optimized condition were chosen in following research.Silica particles in silica sol were transferred into isopropanol by azeotropic distillation, and then treated by SCA(both KH560 and GPPTES), thus hydrophilic silica particles were converted into hydrophobic ones. After evaporating the solvent of the silica/isopropanol sol, and extracting with toluene several times, silica particles obtained were analyzed by Infrared spectrometry (IR) and Thermal Gravity Analysis (TGA). The results confirmed that a considerable amount of SCA molecules were grafted onto the surface of silica particles. Furthermore, the dispersion of silicaparticles in isopropanol sol was investigated by Transmission Electron Microscopy (TEM) and Dynamic Lightening Scattering (DLS), showing that a homogenous dispersion was obtained by SCA modification.The influences of different SCA and their amount on the surface active silanol value of silica were studied by silanol titration with sodium hydroxide. The results suggested that active silanol value was decreased as the increasing of the molecular weight of the SCA and their amount, which suggested that, unlike KH560, SCA with longer molecular chain covered the silanol groups physically besides reacted with them chemically.The rheological behavior of silica/isopropanol sol was studied and a strong shear thinning behavior was observed. On one hand, shear thinning behavior of the sol became apparent with increasing of the chain length and amount of the SCA, on the other hand, it maintained stable when saturation grafting was achieved.The modified silica particles were employed as a modifier for the epoxy adhesives by first dispersing silica/isopropanol sol in the solution of epoxy in acetone by ultrasonic and then evaporating the solvents under vacuum at 50°C.Transmission Electron Microscopy (TEM) was used to observe the dispersion of silica in epoxy adhesives. KH560 modified silica showed slight better dispersion than unmodified silica in an aggregate range of about 100nm, but GPPTES modified silica helped silica particles reached an even more homogenous dispersion in epoxy resin both before curing and after curing with no aggregation.Mechanical properties of silica filled epoxy adhesives were studied. Shear strength and uneven tear strength were both increased by addition of treated silica, but deceased by addition of untreated one. The longer molecular chain of the SCA, the better performance of epoxy adhesive showed in mechanical properties, whichresulted from better dispersion of silica and softer interface. In the range of 1%～5%, when silica particles disperse homogenously in epoxy matrix, shear strength reaches a peak at 2%, while uneven tear strength grows first dramatically(before 2%) and then gently(after2%).更多还原