橡胶用沉淀法白炭黑的现状与发展趋势

介绍橡胶用沉淀法白炭黑的现状和发展趋势。沉淀法白炭黑聚集结构的控制方式有添加表面活性剂、用合适的酸作沉淀剂、二次法沉淀和减少白炭黑表面羟基等。沉淀法白炭黑分散性的测试方法有光学显微镜法和粒径分布测定法。轮胎用白炭黑主要为易分散性白炭黑和高分散性白炭黑。白炭黑产业未来的发展方向是淘汰落后产能,开发补强性和分散性更好的新品种,尤其是能显著降低轮胎滚动阻力的高分散性沉淀法白炭黑。     

Fabrication of silica nanoparticles on the surface of functionalized multi-walled carbon nanotubes

A method for the preparation of a hybrid material consisting of various size silica nanoparticles attached to multi-walled carbon nanotubes (MWCNTs) is proposed. Poly (acrylic acid) oligomer was first reacted with hydroxyl groups on acid-treated MWCNTs leading to a grafted encapsulation of the MWCNTs. These were subsequently reacted with 3-aminopropyltriethoxysilane (APTES) resulting sub-grafting of APTES on the MWCNTs. Such MWCNTs (siloxane-MWCNTs) were further hydrolyzed to make MWCNTs indirectly bearing Si–OH groups. Finally, a bud-like MWCNT/silica hybrid was obtained by forming a number of silica nanoparticles from Si–OH groups on the surface of MWCNTs by introducing siloxane-MWCNTs into a solution of tetraethyl orthosilicate, ammonia, and ethanol. The average size of the silica nanoparticles on the surface of the MWCNTs could be controlled by adjusting the concentration of ammonia and the reaction time.     

Preparation of high purity nano silica particles from blast-furnace slag

High purity nano silica was synthesized using acid treatment and surface modification from blast-furnace slag generated in the steel industry. Blast-furnace slag was treated with nitric acid to extract high-purity insoluble silica. Nano silica was then produced using filtration and surface modified by cation surfactant-Cetyltrimethyl Ammonium Bromide (CTAB). The Zeta potential of silica was tested under various alkaline conditions. Synthesized silica remained electronegative throughout the pH range tested and the number of hydroxyl groups existing on the silica surface was highest when the pH was 9. The size of silica particles was smallest when the modification temperature was 60 °C. The average size of silica particles modified with 3 wt% CTAB was 107.89 nm, while the average size of unmodified silica was 240.38 nm. After extracting silica, pH of the remaining solution was adjusted by adding CaO and then highpurity calcium nitrate crystals were extracted using solubility difference. It was found experimentally that enriching the solution to a high specific gravity (1.63–1.65) before crystallization is preferable for efficient calcium nitrate recovery.     

Control of hydroxyl group content in silica particle synthesized by the sol-precipitation process

This study investigated the control of hydroxyl groups, one of key factors determining the surface properties of silica particles synthesized by the sol-precipitation of tetraethyl orthosilicate (TEOS). Thus, a thermal gravity analysis (TGA) was used to facilitate quantitative measurements of the hydroxyl groups on the silica particles, while BET and FT-IR were used to analyze the specific surface area and functional silane groups on the silica particles, respectively. In the sol-precipitation process, silanes that include various hydroxyl groups are formed as intermediates based on the hydrolysis and condensation of TEOS. Thus, NH₃, as a basic catalyst initiating the nucleophilic substitution of TEOS, was found to accelerate the hydrolysis and increase the hydroxyl group content on the silica particles. Plus, the hydroxyl group content was also increased when increasing the concentrations of TEOS and water as the hydrolysis reactants. However, the hydroxyl group content was reduced when increasing the temperature, due to the promotion of condensation. Based on the weight loss of the particles according to the thermal analysis, the hydroxyl group content on the silica particles varied from 5.6–42.7 OH/nm² under the above reaction conditions.     

Interaction of triton X-100 on silica: A relationship between surface characteristics and adsorption isotherms

Adsorption of Triton X-100 on various silica substrates has been investigated. A number of solids, including a natural quartz, this quartz washed with HCl acid and subsequently heated at 1273 K; two aerosils and one Kieselgel silicas were studied. These solids exhibit surface areas in the range of 5 to 430 m² g^?1. All the Triton adsorption isotherms display an S-shape at the adsorption temperatures studied (298 and 308 K). It has been found that the pretreatments of natural quartz (by water washing, impurities removed by acid and/or high temperature calcination) affect considerably the amounts of TX-100 adsorbed. Measurements of surface composition have been made by X-ray photoelectron spectroscopy (XPS) with particular emphasis on the presence of impurities and on the number of OH groups at the surface of the samples. The nature of the surface hydroxyl has also been studied by infrared spectroscopy. Furthermore, the specific number of hydroxyl groups on the surface of the silica samples has been determined by thermogravimetric analysis. Finally an attempt to correlate solid surface characteristics with adsorption isotherms has been developed.     

溶胶-凝胶法聚丙烯酸丁酯/二氧化硅杂化材料弹性体的制备与表征

用丙烯酸丁酯与少量功能单体共聚,合成了分子链侧基带羟基的聚丙烯酸丁酯(PBA)乳液,然后与硅溶胶混合,用溶胶-凝胶法制备了PBA/SiO2杂化材料弹性体;研究了SiO2含量对杂化材料弹性体力学性能及透光率的影响,并用扫描电子显微镜、傅里叶变换红外光谱、差示扫描量热分析和动态力学性能分析对杂化材料弹性体的结构进行了表征。结果表明,PBA/SiO2杂化材料热压后成为一种力学性能优良的具有一定透光率的弹性体。随着SiO2含量的增加,杂化材料弹性体的力学性能提高,透光率和SiO2粒子的粒径增加,PBA基体的玻璃化转变温度和损耗因子下降;PBA共聚物分子链侧基所带羟基与SiO2粒子表面的硅醇基发生了缩合脱水反应,形成了Si—O—C共价键,使PBA基体与SiO2粒子构成的界面结合紧密,从而赋予杂化材料弹性体以优良的性能。     

The preparation of multi-walled carbon nanotubes encapsulated by poly(3-acrylaminopropylsiloxane) with silica nanospheres on the polymer surface

A silica-polymer-carbon nanotube hybrid was prepared in which the nanotubes were encapsulated by poly(3-acrylaminopropylsiloxane) with silica nanospheres on the polymer surface. First, highly reactive poly(acryloyl chloride) (PAC) was grafted onto the nanotubes through the reaction of side acyl chloride groups with hydroxyl groups present on the surface of acid-oxidized nanotubes. Second, reacting 3-aminopropyltriethoxysilane with the grafted PAC through the reaction between amino and acyl chloride groups, siloxane-containing sub-grafts were introduced onto the primary PAC grafts. Third, silica nanospheres were covalently linked to the sub-grafts by condensation to form a nanotube-polymer-silica hybrid. Each intermediate structure was confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy (TEM). TEM observation revealed a nanostructure in which the nanotube was encapsulated with a polymer layer bearing silica nanospheres on its surface.     

Carbon-coated mesoporous silica with hydrophobicity and electrical conductivity

The pore surface of mesoporous silica SBA-15 was coated with 2,3-dihydroxynaphthalene (DN) through a dehydration reaction between the surface silanol groups in SBA-15 and the hydroxyl groups of the DN molecules. By the carbonization of DN in the SBA-15 pores, the pore surface was uniformly covered with an extremely thin carbon layer, which comprised only 1-2 graphene sheets. The resulting carbon-coated SBA-15 still possessed the characteristics of the original SBA-15—large surface area and pore volume, long-range ordered structure, and sharp mesopore size distribution. In addition, the carbon-coated SBA-15 showed marked hydrophobicity and high electrical conductivity, both of which are not intrinsic properties of SBA-15. The appearance of these features can be explained from the almost perfect carbon coating on the pore surface. Newly developed graphene coating technique can donate characteristic carbon properties to mesoporous silica.     

The effect of fumed silica upon the reaction of iron octoate and polysiloxanes

Silica is a common component in silicone elastomer formulation. Silica is known to have surface hydroxyl groups and the reactions and interactions of these surface groups with various materials have been studied extensively in the past. It is believed that the iron octoate used to combat oxidative embrittlement in silicone elastomer formulations may also react with the surface of silica, specifically fumed silica. Dynamic mechanical spectroscopy (DMS), Fourier Transform Infrared Spectroscopy (FT-IR), Electron Scanning for Chemical Analysis (ESCA), and Gel Permeation Chromatogrphy (GPC) were used to study the influence of untreated fumed silica and silica treated with dimethylsiloxane species on the iron octoate reaction. The rate of reaction was studied as a function of loading of silica. From analyzing rates of backbone scission and salt consumption, it is found that the iron octoate reacts preferentially with the surface of untreated fumed silica. Conversely, iron octoate appears to have no preferential reaction with the surface of the treated fumed silica.     

Characterization of copper-silica catalysts by means ofin Situ diffuse reflectance infrared Fourier transform spectroscopy

Copper silica catalyst precursors have been characterized by diffuse reflectance infrared Fourier transform spectroscopy. The measurements were performed both under atmospheric conditions and under controlled gasatmospheres at elevated temperatures. Two reflection bands at 3615 and 690 cm^–1 have been attributed to hydroxyl vibrations associated with the presence of copper ions highly dispersed over the silica surface. Calcination of a catalyst precursor at 800 K led to the disappearance of the copper-related surface hydroxyl groups.