纳米二氧化硅/凹土复合材料的制备以及吸附性能

以硅酸钠为主要原料,用硫酸调节pH,通过液相沉淀法在凹土单晶表面原位生成纳米粒状二氧化硅,制备纳米二氧化硅/凹土复合粉体。利用XRD、TEM、TG-DTG、氮气吸附脱附曲线等方法对复合粉体进行表征。XRD表明,二氧化硅以非晶态的形式包覆在凹土表面,防止了凹土的团聚。TEM照片显示,包覆后的纳米二氧化硅粒径减小,粒度分布均匀,表面光滑。     

高纯纳米SiO2制备

以煤矸石为原料,制备了低成本纳米二氧化硅(SiO2.xH2O)。采用红外光谱、XRD、TEM等技术对产物进行了表征,结果表明制备的纳米二氧化硅粉体呈球形、粒径分布范围为15～20 nm,纯度高于99.98%。     

碳酸钙／二氧化硅纳微复合粒子的高能球磨制备

采用高能球磨法制备了碳酸钙(纳米)/二氧化硅(微米)复合粒子.用X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、能谱分析仪(EDS)和傅里叶变换红外光谱仪(FT-IR)研究了球磨过程中复合粉体的相组成和微观组织;对碳酸钙/二氧化硅复合粒子的粒径、形态、结构进行了测定与表征.结果表明随着球磨时间的延长,复合粉体在强烈的冲击、挤压作用下逐渐细化和均匀化;球磨240 min可形成结合紧密的碳酸钙/二氧化硅复合粒子,并使之球形化;纳米碳酸钙均匀复合于二氧化硅的表面及其空隙,复合过程中没有产生新物质;强烈的机械力作用,使纳米碳酸钙表面晶体结构发生畸变,颗粒表面无定形化程度增加.     

不同煅烧温度下SiO2/TiO2复合粉体的制备与表征

实验以硅酸钠为原料制备比表面积较大的二氧化硅粉体,再以硫酸氧钛为钛源、二氧化硅为载体在一定温度、pH条件下反应制备复合粉体。探讨了不同的煅烧温度对产物的催化性能的影响,并进行了XRD、红外光谱等方面的性能表征。结果表明500℃下煅烧的催化效果最好,对活性大红染料降解率高达99.45%     

铜改性凹凸棒石/纳米二氧化钛复合粉体的微观结构

以四氯化钛作前驱体,采用酸碱中和并流法制备了以铜改性凹凸棒石为载体的表面包覆纳米氧化钛的复合粉体.用高分辨透射电镜和X射线衍射(X-ray diffraction,XRD)对该纳米复合粉体的微观结构进行观察和分析.实验结果显示:二氧化钛以3～6nm的晶体颗粒粘附在一维纳米棒状的凹凸棒石表面.凹凸棒石和氧化钛均各自相互分离,没有团聚现象发生.纳米复合粉体中的氧化钛为单一类型的锐钛矿相,其XRD衍射峰和JCPDS的锐钛矿特征衍射峰一致.凹凸棒石的主要特征衍射峰位置没有发生较大变化.铜以多价态的形式存在于凹凸棒石表面.该复合粉体对大肠杆菌和金黄色葡萄球菌的24h抑菌率分别达到了99.52%和99.15%.     

沉淀-超声法制备纳米二氧化硅

在化学沉淀超声分散条件下,研究了体系pH值、表面活性剂种类、分散剂用量、干燥方式、超声分散等因素对产物纳米二氧化硅粒径的影响。通过实验确定了沉淀-超声法制备纳米二氧化硅的最佳工艺条件。采用XRD、TG-DTA及激光粒度仪等测试手段对产物进行了表征。结果表明:在最佳工艺条件下制得了粒径为40 nm的二氧化硅粉体。研究表明,沉淀-超声法是一种制备纳米二氧化硅的简单的新方法,所得粉体粒径小,粒径分布窄,实验条件要求低,操作简便、易行,便于工业化生产。     

无皂丙烯酸树脂/SiO2纳米复合皮革涂饰剂的研究

以过硫酸钾为引发剂，丙烯酸、丙烯酸丁酯和丙烯酸甲酯为单体，并加入纳米二氧化硅粉体，采用无皂乳液聚合法制备丙烯酸树脂／SiO2纳米复合涂饰剂。研究单体配比、pH值、引发剂用量及温度对乳液性能和聚合物膜的物理机械性能的影响；采用红外光谱和透射电镜对无皂乳液和纳米复合涂饰剂进行检测，并对无皂乳液和纳米复合涂饰剂膜进行了DSC测试。     

凝胶网格沉淀法制备纳米二氧化硅

主要研究了凝胶网格沉淀法制备纳米二氧化硅的工艺条件,如:琼脂用量、HCl浓度、SiO32-离子浓度、反应物物质的量比(H /SiO32-)等因素对产物粒径的影响。实验确定制备纳米二氧化硅的最佳工艺条件为:琼脂质量分数为11.5%,盐酸浓度为0.6mol/L,硅酸钠浓度为0.4mol/L,最佳配比(SiO23-/H )为1:2.1。采用XRD、TG-DTA及透射电镜等测试手段对产物进行了表征。研究表明:采用凝胶网格沉淀法可制得平均粒径为40nm的二氧化硅粉体,凝胶网格沉淀法是一种制备纳米二氧化硅的简单的新方法,所得粉体粒径小,粒径分布窄,实验条件要求低,操作简便、易行,便于工业化生产。     

甲基乙烯基硅橡胶/有机蒙脱土母炼胶纳米复合材料的制备、结构与性能

采用溶液插层法和母炼胶混炼工艺制备了甲基乙烯基硅橡胶(MVQ)/有机蒙脱土母炼胶(OMMT-MB)纳米复合材料,通过X射线衍射(XRD)、透射电子显微镜(TEM)对复合材料进行了表征,研究了复合材料的拉伸性能与热稳定性能,并与直接共混法制备的MVQ/有机蒙脱土(OMMT)复合材料和MVQ/白炭黑复合材料进行了对比,分析了OMMT的增强机理.结果表明,MVQ/OMMT-MB纳米复合材料中的OMMT完全剥离,且均匀分散在MVQ基体中;当OMMT质量分数为20%时,MVQ/OMMT-MB复合材料的拉伸性能优于MVQ/OMMT复合材料,拉伸强度和扯断伸长率分别增大至1.41 MPa、490%;其与MVQ/白炭黑复合材料相比,两者的拉伸强度相当,扯断伸长率增大了30%;MVQ/OMMT-MB复合材料的热稳定性略优于MVQ/OMMT复合材料,但比MVQ/白炭黑复合材料差.     

氟硅酸铵氨化制备纳米二氧化硅的实验研究

实验以氟硅酸铵和氨水为原料,通过化学沉淀法制备纳米二氧化硅粉体。考察了表面活性剂、反应温度、物料配比等不同工艺条件对纳米二氧化硅粉体的粒度分布、反应收率等的影响。实验结果表明:分散剂十二烷基苯磺酸钠可以有效改善粉体粒度的分布;综合考虑二氧化硅粉体的粒度、反应收率、反应效率和生产成本,确定氟硅酸铵氨化制备二氧化硅的反应温度为常温、反应时间为60 min、物料配比(氟硅酸铵与氨水物质的量比)为1∶4.8、氨水的加料速度为96 m L/min、搅拌速度为200~300 r/min。     

Effect of KH550 on the Preparation and Compatibility of Carbon Fibers Reinforced Silicone Rubber Composites

Silicone rubber has good heat resistance, but its mechanical properties are poor. To improve the mechanical properties of the silicone rubber, the carbon fiber / silicone rubber composites were prepared in this paper, in which the silicone rubber was used as the matrix, the high-performance carbon fiber (CF) treated with coupling agent is used as the reinforcement. The best composite formulation, the types and content of coupling agent are determined by testing mechanical properties of the composites. The morphology structures of the composites were observed by scanning electron microscope (SEM), the compatibility between carbon fiber and silicone rubber was studied by infrared spectrum analysis (IR), dynamic thermal mechanical analysis (DMA) and X-ray photoelectron spectroscopy (XPS). The results show that the best composite formulation is silicone rubber of 100 phr, carbon fiber of 12 phr, coupling agent KH550 of 2.5 phr. The best first curing conditions are at 175 ^°C under 10 MPa for 30 min, the postcuring conditions are at 200 ^°C for 2h. The compatibility between carbon fiber treated with KH550 and silicon rubber is the best by SEM, IR, DMA and XPS analysis, and confirm that the coupling agent KH550 plays a compatilizer role in the preparation process of the carbon fiber/silicone rubber composites.     

The synthesis,characterization and properties of silicone adhesion promoters for addition-cure silicone rubber

Two types of polysiloxanes, GVPMS and GVHMS, were synthesized through nonhydrolytic sol-gel reaction from vinyltrimethoxysilane(VTMS), 3-glycidoxypropyltrimethoxysilane(KH560) and diphenylsilandiol(DPSD) or hydroxyl silicone oil, respectively. The chemical structures were characterized by Fourier transform infrared (FTIR) spectroscopy, ¹H nuclear magnetic resonance (¹H-NMR) spectroscopy and gel permeation chromatography (GPC). GVPMS and GVHMS were used as adhesion promoter for addition-cure silicone rubber. It was found that the adhesion promoters not only greatly improved adhesion strength but also had excellent compatibility with silicone rubber. Among them, GVPMS gave better adhesion strength in silicone rubber. The shear strength of silicone rubber reached 1.70 MPa with addition of 1.5 phr GVPMS, which was about 317% higher than that of silicone rubber without the adhesion promoter. Meanwhile, the shear strength of silicone rubber reached 1.14 MPa with addition of 2.0 phr GVHMS, which was 183% higher than that of silicone rubber without the adhesion promoter. Optical property test results revealed that the refractive indexes of GVPMS and GVHMS were 1.5185 and 1.4133 respectively and both of them had good compatibility with silicone rubber, which satisfied the application demand of high-refractive and low-refractive electron encapsulation. Thermal resistance test and SEM results further proved that adhesion promoter could significantly increase the adhesion between the copper substrate and silicone rubber, in which GVPMS had a better performance. Oxidation treatment experiment further explained the mechanism that adhesion promoter functioned as a bridge, linked silicone rubber and copper substrate through chemical bonds.     

Effect of tetraphenylphenyl‐modified fumed silica on silicone rubber radiation resistance

Two kinds of treated fumed silica were prepared by treatment with either tetraphenylphenyltriethoxysilane (TPHTS) or both tetraphenylphenyltriethoxysilane and hexamethyldisilazane (TPHMTS), and were used as reinforcing filler for silicone rubber. The resistance to irradiation of the silicone rubber obtained was investigated by gamma ray of dose 500 kGy in air. The mechanical properties and the average molecular weight between crosslinking points (Mc) of the silicone rubber were determined before and after irradiation. The results show that the fumed silica treated by tetraphenylphenyltriethoxysilane (TPHPHS) can effectively improve the radiation resistance of silicone rubber while the fumed silica treated by both tetraphenylphenyltriethoxysilane and hexamethyldisilazane (MM^N) cannot only effectively improve the radiation resistance of silicone rubber but also has excellent reinforcing effect on silicone rubber. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

MP/OMMT对脱醇型RTV阻燃硅橡胶性能的影响

以α,ω-二羟基聚二甲基硅氧烷(107硅橡胶)、甲基三乙氧基硅烷、三聚氰胺磷酸盐(MP)和纳米有机蒙脱土(OMMT)为原料,制备了脱醇型室温硫化(RTV)阻燃硅橡胶。研究了MP/OMMT配比对脱醇型RTV硅橡胶阻燃性能、动态燃烧性能和机械性能、热稳定性的影响,用扫描电镜(SEM)考察了MP、OMMT在RTV硅橡胶中的分散情况。锥形量热仪和极限氧指数测试结果表明,随着OMMT用量的增多和MP用量的减少,硅橡胶的阻燃性能没有显著的变化;热失重分析表明,OMMT的添加使硅橡胶的初始分解温度明显提高,大大提高了硅橡胶燃烧残渣的生成量;机械性能测试表明,OMMT的增多能明显提高硅橡胶的机械性能。与只添加MP的硅橡胶相比,当MP和OMMT各添加20份时,硅橡胶的极限氧指数下降0.6%,初始分解温度提高了95℃,拉伸强度、硬度、撕裂强度分别提高48.6%、4.7%、50.9%;此时的SEM分析表明,OMMT能在硅橡胶中均匀分散,且燃烧残渣表面变得平整、坚硬、致密。即在此配比下硅橡胶能在保持良好阻燃性的同时提高其机械性能。     

有机杂化纳米CaCO3/SiO2复合粒子对硅橡胶性能的影响

以纳米碳酸钙（CaCO3）为原料,采用溶胶沉积法制备出具有核/壳结构的纳米CaCO3/SiO2复合粒子,并将其原位有机杂化。用纳米CaCO3/SiO2复合粒子替代部分气相法白炭黑作为硅橡胶的补强填料,采用扫描电子显微镜、拉力试验机、热失重仪等对改性硅橡胶的力学性能和热稳定性能进行表征。结果表明：有机杂化剂的种类不同,纳为CaCO3/SiO2复合粒子对硅橡胶的补强效果不同;与用未杂化的纳米CaCO3/SiO2复合粒子取代部分气相法白炭黑的硅橡胶相比,用经A-151杂化的复合粒子取代部分气相法白炭黑的硅橡胶,其拉伸强度、断裂伸长率得到明显改善,耐热性也得到提高;但撕裂强度大大降低。同时还发现,硅橡胶的力学性能及耐热性能在很大程度上也与复合粒子的取代量有关;即使是经KH-570杂化的复合粒子,当取代量小于10%时,其硅橡胶的性能也优于全部用气相法白炭黑补强的硅橡胶。     

金属氢氧化物对室温硫化硅橡胶陶瓷化性能的影响

以α,ω-二羟基聚二甲基硅氧烷(107硅橡胶)为基体,金属氢氧化物(氢氧化铝和氢氧化镁)为陶瓷化助剂,制备可陶瓷化室温硫化(RTV)硅橡胶,研究金属氢氧化物对硅橡胶性能的影响。结果表明:与未添加金属氢氧化物的硅橡胶相比,添加氢氧化镁的硅橡胶的力学性能明显降低,而添加氢氧化铝的硅橡胶的力学性能变化不明显;与添加氢氧化镁的硅橡胶相比,添加氢氧化铝的硅橡胶在1 000℃烧蚀后所得陶瓷体的外观更加稳定,形状保持更好,陶瓷体断面更致密;添加氢氧化铝的硅橡胶陶瓷体的三点弯曲强度比未添加金属氢氧化物的硅橡胶陶瓷体显著增大。     

氢氧化镁阻燃硅橡胶的制备及性能

分别采用未处理氢氧化镁、有机硅处理氢氧化镁、硬脂酸处理氢氧化镁为阻燃剂,制备阻燃硅橡胶,研究了氢氧化镁种类对硅橡胶阻燃性能、力学性能、电性能的影响;通过扫描电镜观察阻燃硅橡胶的拉伸断面形貌,并通过热重分析对硅橡胶的阻燃机理进行初步探讨。结果表明,采用经有机硅处理的氢氧化镁为阻燃剂时,硅橡胶的阻燃效果优于采用其它两种氢氧化镁为阻燃剂的硅橡胶;有机硅处理氢氧化镁对硅橡胶的力学性能和电性能损害较小。添加60份有机硅改性氢氧化镁时,硅橡胶的极限氧指数达到36%,拉伸强度为6.4MPa,撕裂强度为32.9kN/m,邵尔A硬度为51度,体积电阻率和表面电阻率分别为5.8×1015Ω.cm和4.1×1015Ω,介电常数和介质损耗因数分别为3.43和2.34×10-2。有机硅处理氢氧化镁在硅橡胶中分散较均匀,界面结合紧密,孔洞较少。     

梯形聚甲基倍半硅氧烷对脱醇型RTV-1硅橡胶性能的影响

以甲基三氯硅烷为主要原料,乙二胺为梯形控制剂,合成了梯形聚甲基倍半硅氧烷(PMSQ);以八甲基环四硅氧烷(D4)为原料,采用碱催化平衡聚合法,制备了α,ω-二羟基聚二甲基硅氧烷(107硅橡胶);采用107硅橡胶、交联剂、PMSQ等制备了脱醇型单组分室温硫化(RTV-1)导热硅橡胶。探讨了PMSQ用量对RTV-1硅橡胶导热、绝缘、物理性能、阻燃和热稳定性的影响。结果表明,温度高于90℃时,随PMSQ用量的增加,硅橡胶的热导率增大;当其用量为2.5 g(以50 g 107硅橡胶为基准)时,硅橡胶在30～150℃具有较好的导热性能。随PMSQ用量的增加,硅橡胶的拉伸强度、断裂伸长率均逐渐下降;硅橡胶的体积电阻率随PMSQ的增加先增后减,添加量为1.5 g时,体积电阻率增大了1.68倍。PMSQ能提高RTV-1硅橡胶的阻燃性能,并且能提高硅橡胶的热稳定性,减轻了RTV-1硅橡胶高温下迅速分解的状况,延缓了热失重的速度,PMSQ的较佳用量为2.5 g,此时,硅橡胶的热导率为0.425 W/m·K,拉伸强度为3.5 MPa,拉断伸长率为188%,体积电阻率为4.0×1015Ω·cm。     

Effect of CeO2 on UV aging of composite insulators prepared by template-spraying method

When the silicone rubber composite insulator is exposed outdoors for a long time, it will be affected by high-temperature ultraviolet environments. In order to ensure the operation of silicone rubber composite insulators, a super-hydrophobic composite insulator with antiaging characteristics was prepared by mixing cerium dioxide (CeO₂) with silicone rubber and spraying CeO₂ on the surface of silicone rubber. This article studied the aging characteristics of the base and surface of silicone rubber composite insulator by CeO₂ in ultraviolet environment. The properties of silicone rubber composite insulators before and after aging were tested by mechanics, contact Angle, rolling Angle, bounce, and icing experiments. The aging mechanism of silicone rubber was analyzed by Fourier transform infrared spectroscopy and search engine marketing. This study prepared composite insulators with excellent mechanical, hydrophobic, and antiicing properties. The aging resistance of silicone rubber composite insulators is improved by adding CeO₂ into silicone rubber matrix and spraying CeO₂ on the surface, which also ensure the use of composite insulators in high-temperature ultraviolet environment.     

Microcellular foaming of silicone rubber with supercritical carbon dioxide

In spite of great concern on the industrial application of microcellular silicone rubber foams, such as in electric and medical devices, only a few works can be found about the foaming of silicone rubber. In this study, microcellular silicone rubber foams with a cell size of 12 μm were successfully prepared with curing by heat and foaming by supercritical CO₂ as a green blowing agent. The microcellular silicone rubber foams exhibited a well-defined cell structure and a uniform cell size distribution. The crosslinking and foaming of silicone rubber was carried out separately. After foaming, the silicone rubber foam was cross-linked again to stabilize the foam structure and further improve its mechanical properties. Foaming process of cross-linked silicone rubber should be designed carefully based on the viscoelastic properties because of its elastic volume recovery in the atmosphere. The basic crosslinking condition for small cell size and high cell density was obtained after investigating the rheological behavior during crosslinking.