不同偶联剂对介孔分子筛MCM-41的表面修饰及对MCM-41/环氧树脂性能的影响

使用2种硅烷偶联剂(KH550和KH792)对介孔分子筛MCM-41进行表面改性,采取氮气吸附-脱附、FTIR和TGA等进行表征,并采用原位聚合法制备了MCM-41/环氧树脂复合材料,研究了偶联剂种类和MCM-41用量等对复合材料固化过程及性能的影响。结果表明:硅烷偶联剂可与MCM-41表面的硅羟基反应,在分子筛内外表面接枝上功能化基团。经表面修饰的MCM-41比表面积下降为原来的1/5,KH550在MCM-41表面接枝率仅为KH792的一半。KH550与MCM-41外表面反应得更充分,KH792对MCM-41孔道内壁的修饰效果更强。固化动力学结果表明:KH792的功能化基团有伯胺和仲胺,与环氧树脂具有更高的反应活性,但不利于环氧大分子进入孔道,仅以球形粒子的形式添加在环氧树脂中;KH550表面修饰的MCM-41可使环氧大分子进入孔道内形成互穿结构。KH550表面修饰体系更多体现出MCM-41多孔的特征,形成了有机-无机互穿结构的复合体系,大幅度提高了储能模量和玻璃化转变温度。KH792表面修饰体系则呈常规球形纳米粒子的特征,其储能模量和玻璃化转变温度较纯环氧树脂有所提高但幅度不大。     

表面接枝防老剂的白炭黑在天然橡胶中的应用

为了提高白炭黑与橡胶的相容性,同时防止防老剂的挥发,采用γ-缩水甘油醚氧丙基三甲氧基硅烷与对氨基二苯胺(PPDA)的反应物对白炭黑进行表面改性,得到表面接枝防老剂的白炭黑。将改性白炭黑应用于天然橡胶(NR)中考察其增强与防老性能,并与炭黑/NR、未改性白炭黑/NR和Si69改性白炭黑/NR复合材料相比较(均添加防老剂4020)。结果表明,改性白炭黑/NR复合材料的焦烧时间延长,硫化时间缩短,白炭黑在橡胶中的分散性提高,同时具备更出色的力学性能。随着表面接枝防老剂含量的增加,改性白炭黑/NR复合材料的拉伸强度和撕裂强度比未改性白炭黑和Si69改性白炭黑/NR均有大幅提高。当接枝的PPDA含量达到5.27%(与白炭黑的质量比)时,其拉伸强度比未改性白炭黑/NR提高了90%,比Si69改性白炭黑/NR提高了73%,并接近炭黑/NR; 其撕裂强度是未改性白炭黑/NR的5倍,Si69改性白炭黑/NR的2.5倍,炭黑/NR的2倍。另外,表面接枝防老剂的白炭黑/NR复合材料具有优异的抗热氧、抗臭氧和湿热老化性能;其抗臭氧老化性能优于添加通用防老剂4020的对比复合材料。     

纳米介孔MCM-41-M/偶联剂体系对天然橡胶性能的影响

制备了天然橡胶(NR)/MCM-41-M、NR/偶联剂化学改性纳米介孔MCM-41-M、NR/MCM-41-M/偶联剂复合材料,研究了不同含量的MCM-41-M、不同种类偶联剂对MCM 41-M的改性以及偶联剂的添加方式对NR复合材料性能的影响.结果表明;MCM-41-M在NR中有明显的补强作用,当代替3份炭黑时NR基复合材料的拉伸强度达到最大值,比纯NR提高了12.7%。与MCM-41-M和KH-570直接添加到NR中相比,MCM-41-M经偶联剂KH-570改性使拉伸强度提高了50%。将MCM-41-M用偶联剂KH 570改性后添加到NR中,使NR的玻璃化转变温度升高、玻璃化转变区的损耗角减小、储能模量提高到最大。     

白炭黑的功能化改性及其改性橡胶基复合材料的制备与表征

利用沉淀法白炭黑生产工艺,在相同的条件下,选用不同质量分数的羟基羧酸酯作为改性剂进行湿法改性,研究了白炭黑/天然橡胶(NR)复合橡胶的力学性能、动态性能以及动态生热性能。结果表明:制备的白炭黑均为非晶态白炭黑,采用质量分数为6%的羟基羧酸酯改性的白炭黑,其分散性好,颗粒分布均匀,呈近球状,经羟基羧酸酯改性后的白炭黑有效的去除了部分亲水基团,改善了其在NR中的分散性。随着白炭黑用量的增加,分散性变差,损耗因子和动态温升均有所提高,Payne效应增大。当白炭黑用量达到临界值(白炭黑与NR质量比为40∶100)时,白炭黑/NR复合材料表现出较好的性能,改性白炭黑/NR复合材料比未改性白炭黑/NR复合材料的硬度、拉伸强度、断裂伸长率有所提高,而磨耗体积和动态生热则有所下降。动态力学性能测试结果表明,改性白炭黑与天然橡胶的质量比为40∶100时,改性白炭黑/NR复合材料的60℃滚动阻力损耗因子由0.123降到0.104。SEM结果表明,改性白炭黑在橡胶基体中的分散性优于未改性白炭黑,与NR基体界面结合的更加紧密。     

Preparation and characterization of epoxy nanocomposites by using PEO-grafted silica particles as modifier

EP/SiO₂ nanocomposites, which contained PEO flexible chain, have been prepared via epoxy resin and PEO-grafted silica particles. The PEO-silica particles were obtained by endcapping PEO-1000 with toluene 2,4-diisocyanate (TDI), followed by a reaction with silica sols. The chemical structure of the products was confirmed by IR measurements, and the mechanical properties of composites such as impact strength, flexural strength, dynamic mechanical thermal properties were investigated. The results showed that the addition of the PEO-grafted silica particles to the epoxy/DDS curing system, the impact strength is 2 times higher than that of the neat epoxy. While the storage modulus and the glass transition temperature are a little changed. The morphological structure of impact fracture surface and the surface of the hybrid materials were observed by scanning electron microscope (SEM) and atomic force microscopy (AFM), respectively.     

Influence of selected alkoxysilanes on dispersive properties and surface chemistry of spherical silica precipitated in emulsion media

The process of silicas formation in emulsion system in the reaction of precipitation from water solutions of sodium silicate and hydrochloric acid has been studied. The effects of silica surface modifications with silane coupling agents from the group of alkoxysilanes with different functional groups have been determined. Both unmodified and modified silicas have been thoroughly characterised by scanning electron microscopy (SEM) and dynamic light scattering (DLS) and other methods.The effect of alkoxysilanes on the diameter distribution of the modified silica is insignificant; the presence of silane coupling agents causes a small increase in the particle diameter and a small increase in the tendency towards agglomeration, moreover the particles of silicon dioxide precipitated are characterised by spherical shape. The course of the electrokinetic curves depends mainly on the proton affinity of the modifiers. Significant changes in the stability of silica dispersions have been found as a result of modification with N-2-(aminoethyl)-3-aminopropyltrimethoxysilane. This compound causes the greatest increase in the tendency towards agglomeration of the primary particles. The modification mechanism has been established to be chemisorption, as indicated by the ¹³C and ²⁹Si CP MAS NMR spectra. The products have been shown to have typical mesoporous structure. The surface area of the unmodified silica is 133 m²/g, while those for the modified silicas vary from 115 to 182 m²/g.     

不同改性白炭黑填充天然橡胶的流变性能EI北大核心CSCD

通过橡胶加工分析仪和毛细管流变仪分别研究了添加偶联剂KH560、Si69、NXT和不加偶联剂的白炭黑填充天然橡胶的填料网络结构,考察了不同偶联剂对白炭黑填充NR的流变形为的影响。结果表明,3种偶联剂均改善了白炭黑的表面特性,使白炭黑填料网络化程度减轻,储能模量和损耗模量变小,Payne效应大大减弱,改善了加工性能。其中偶联剂NXT的改性综合效果最佳。     

Modified zinc silicate — an active rubber filler

Physico-chemical properties have been characterized for zinc silicates obtained in various conditions in reaction of sodium metasilicate solution with water soluble zinc salt (zinc sulphate or chloride). Attempts have been made to apply the precipitated zinc silicates in rubber mixtures based on butadiene-styrene rubber. Appropriate tests have been conducted. Also, a possibility has been tested of eliminating zinc oxide (an activator in the vulcanization process) from the rubber mixture. Studies have been presented on the modification of zinc silicate surface with silane and titanate coupling agents. The extent of surface modification has been estimated measuring heats of surface immersion and determining chemisorbed carbon on the surface which has originated from coupling agents. The effect of modifying zinc silicate surface has been evaluated by strength tests performed on vulcanizates filled with the modified silicates.     

改性白炭黑/天然橡胶复合材料的制备及性能

采用双-[γ-(三乙氧基硅)丙基]四硫化物(Si69)、γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)、乙基三甲氧基硅烷(11-100)对白炭黑进行表面改性,并制备改性白炭黑/天然橡胶复合材料。利用红外光谱(FT-IR)、热重分析(TG)、扫描电镜、橡胶加工分析仪等测试手段对改性白炭黑及改性SiO_2/NR复合材料的结构与性能进行了表征,并研究其硫化性能及力学性能。结果表明,经FT-IR、TG分析,3种硅烷偶联剂已成功接枝到白炭黑表面;改性SiO_2/NR复合材料相对于未改性SiO_2/NR,焦烧时间变长,正硫化时间缩短,结合胶含量增大;改性SiO_2/NR与未改性SiO_2/NR相比其定伸应力、撕裂强度明显提高,但断裂伸长率有所减小;改性白炭黑在天然橡胶基体中的分散性明显提高,其中Si69-SiO_2在天然橡胶基体中的分散性最好;Si69-SiO_2/NR复合材料的滚动阻力与生热最低;改性后的SiO_2/NR复合材料的拉伸断面粗糙程度增加。     

Mechanical properties of nano-silica particulate-reinforced epoxy composites considered in terms of crosslinking effect in matrix resins

In this study, the mechanical properties of nano-silica particulate-reinforced epoxy composites with different crosslinking densities were clarified experimentally to consider the interaction effects between nano-particles and the network structure in matrix resin. The matrices were prepared by curing with an excessive mixture of diglycidyl ether of bisphenol A type epoxy resin as the curing agent for the stoichiometric condition. The volume fraction of the silica particles with a median diameter of 240 nm was constantly 0.2 for every composite. The crosslinking densities and glass transition temperatures of the neat epoxy resins were identified from thermo-viscoelastic properties measured by dynamic mechanical analysis. Elastic moduli and strengths of the composites and the neat epoxy resins were measured by three-point bending tests. The glass transition temperatures of the neat epoxy resins decreased linearly as the crosslinking densities decreased from the stoichiometric condition. The glass transition temperatures of the composites were reduced by adding the nano-silica particles. The bending moduli of the composites in the glassy state could be predicted by using a mixture law of the composites regardless of the crosslinking densities and glass transition temperatures. The bending strengths were found to be sensitive to the crosslinking densities: they were both higher (for composites with high crosslinking densities) and lower (for composites with low crosslinking densities) than those of the neat epoxy resin. These results demonstrate that the interaction between nano-particles and network structures reduces the bending strengths, especially for low crosslinking densities.     

The effect of surface modification on physicochemical properties of precipitated silica

The main goal of this study was to obtain hydrophobic silica whose properties would allow their application as plasto- and elastomer fillers. Thus, hydrated silica was modified by silane and titanate coupling agents. The modification procedure and appropriate modification apparatus were developed. The degree of silica surface modification was evaluated by different methods. As grounds for this evaluation, changes in the physicochemical properties, brought about by the condensation reaction of surface silanol groups with alkoxyl or hydroxyl groups of the molecules of coupling agents, were used. The degree of hydrophobicity of the silica surface was determined on the basis of the heat of immersion of this surface, and silanol groups were identified by the infrared spectroscopy. Moreover, changes in the tendency to form agglomerates and aggregates of molecules were studied by microscopy. It was found that modification with silane and titanate coupling agents leads to an increase in silica activity. Application of these agents results in the change of the hydrophilic character to the hydrophobic one. This revised version was published online in November 2006 with corrections to the Cover Date.     

偶联剂改性纳米硅溶胶的接枝率及稳定性

为改善纳米硅溶胶与有机物间的亲和性及分散稳定性,用硅烷偶联剂对碱性纳米硅溶胶进行表面接枝改性。分析了偶联剂用量、反应温度和反应时间对接枝率、分散稳定性及微观形貌的影响。结果表明,偶联剂KH560更适合做碱性纳米硅溶胶的表面改性剂,且制备的改性纳米硅溶胶表面可接枝KH560;从接枝率变化梯度来看,KH560用量对接枝率影响最大,当KH560含量为12.5%、反应时间为5h、反应温度为60℃时,改性接枝率及Zeta电位绝对值最高,分别为7.37%和55.6mV。     

钛酸钾晶须填充新型PPESK的性能及形态研究

采用填料对含二氮杂萘结构的聚醚砜酮(PPESK)进行填充改性,能够快捷有效的提高其性能,为此采溶液共沉析的方法制备了含二氮杂萘结构的聚芳醚砜酮/钛酸钾晶须(PPESK/Whisker)复合材料.使用不同比例的钛酸酯偶联剂进行晶须表面处理,研究了晶须表面处理和晶须含量对PPESK复合材料机械性能的影响;考察了复合材料的热性能,并用扫描电镜观察了复合材料的形貌.结果表明,钛酸钾晶须作为填充材料,使得复合材料机械性能得到明显改善;对晶须进行适当的表面处理后,晶须与PPESK基体的相容得到改善.     

空心玻璃微球含量对环氧复合泡沫塑料性能的影响

以空心玻璃微球（HGM）填充环氧树脂制备了密度为0.56~0.91 g/cm3的HGM/环氧复合泡沫塑料。研究了HGM含量对复合泡沫塑料黏度、力学性能、动态力学性能及隔热性能的影响。结果表明:表面偶联处理后增加了HGM的表面亲油性,改善了其与基体树脂间的相容性和界面性能,有利于HGM/环氧复合泡沫塑料性能的提高;体系黏度与HGM含量呈正相关,与温度呈负相关;随着HGM含量的增加,HGM/环氧复合泡沫塑料的压缩强度、弯曲强度和拉伸强度均有一定程度的降低,但是比强度变化不大,材料得到很大程度的轻质化;HGM的引入使得HGM/环氧复合泡沫塑料玻璃化转变温度向低温方向偏移,储能模量呈现先减小后增加的趋势,导热系数由纯环氧树脂的0.203 W/（m·K）减小到HGM含量为40wt%时的0.126 W/（m·K）。HGM/环氧复合泡沫塑料阻尼性能和隔热性能均有所提高。      

废胶粉的表面处理及在天然橡胶中的应用

采用硅烷偶联剂KH550对废胶粉进行表面处理,并将处理后的废胶粉与天然橡胶复合制备WRP/NR复合材料。借助L16(45)正交试验及单因素试验,探讨了废胶粉目数、废胶粉用量、硅烷偶联剂KH550用量对复合材料力学性能的影响;对处理后的废胶粉表面和橡胶拉伸试样断裂面进行了扫描电镜(SEM)观察;并通过热重分析研究了天然橡胶和复合材料的热降解性能。结果表明:当废胶粉目数为80目,废胶粉用量为10%,硅烷偶联剂KH550用量为1.5%时,复合材料的力学性能最优,拉伸强度为27.89MPa。SEM结果表明废胶粉表面粗糙度增大,比表面积增大,与NR基体的相容性得到了提高。而热重分析表明改性废胶粉的加入对天然橡胶的热稳定性能影响不大。     

纳米ATO粉体的表面改性研究

采用偶联剂对纳米ATO(氧化锡锑)粉体进行表面改性,综合考察了偶联剂的品种与用量、反应时间及反应温度对表面改性效果的影响,从而确定最佳表面改性条件.利用红外光谱(FTIR)、热重分析(TGA)以及光吸收率等表征手段来研究表面改性的效果及分散状况.结果表明,纳米ATO粉体表面改性的最佳条件为:选用硅烷偶联剂KH570,添加量为2份,反应水浴温度为80℃,反应5h.     

Thermal stability,morphology, and X-ray diffraction studies of dynamically vulcanized natural rubber/chitosan blends

The thermal degradation behavior of cross-linked Natural Rubber/Chitosan (NR/CS) blends was studied by thermogravimetric analysis (TGA). Dicumyl peroxide (DCP) was selected as a cross-linking agent. Peroxide-cured NR/CS blends exhibit very good overall thermal properties. The activation energy of degradation was analyzed using the Horowitz–Metzger equation. Vulcanization of rubber phase in the blend increased the activation energy. From the activation energy values, it is found that among the series of the blend compositions, NR₈₅CS₁₅ blend vulcanized with 3 pphr DCP exhibits better thermal stability. Better adhesion between the two phases with the incorporation of DCP is achieved which results in an enhancement in the thermal stability. The DSC curve shows that, the T _g of chitosan in the blend increased to 242 °C by dynamic vulcanization. The morphology of the vulcanized blends was studied by scanning electron microscopy. More uniform distribution was exhibited by the vulcanization of NR phase in the blend. X-ray diffraction (XRD) study shows an enhancement in the crystallinity by vulcanization.     

表面处理对水镁石/EVA复合材料界面作用的影响

选用了三种表面处理剂(硬脂酸Ste、硅烷偶联剂KH550、钛酸酯偶联剂JN114)对水镁石进行表面改性,研究了界面作用对复合材料静态力学性能、动态力学性能及粉体分散行为的影响,并对界面粘接强度进行了定量表征。结果表明,表面处理剂的加入明显改善了水镁石粉体在树脂相EVA中的分散性;硬脂酸赋予体系高的断裂伸长率,KH550赋予体系更高的拉伸强度,JN114赋予体系更好的综合性能;由DMTA的损耗因子值(tanδ)计算得出界面粘接强度相对大小依次为:KH550 modified>JN114modified>No treated>Ste modified,此结论与Tg值大小及力学测试数据完全吻合。     

聚丙烯酸酯/纳米二氧化硅复合材料的研究进展

综述了国内外聚丙烯酸酯/纳米二氧化硅复合材料的研究进展.主要内容包括：聚丙烯酸酯/纳米二氧化硅复合材料的制备方法,如常规乳液聚合、微乳液聚合、溶胶-凝胶反应等方法;复合材料制备中无机粒子表面的修饰,着重对目前最常用的硅烷偶联剂和偶氮类化合物两种修饰方法进行了介绍;聚丙烯酸酯/纳米二氧化硅复合材料在光学、涂料、胶粘剂等工业领域中的应用以及复合材料未来应用前景的展望。     

Effects of Nanoparticles on Properties of Modified Polyimide Epoxy Adhesive

Polyimide modified epoxy adhesive(J-27H)/nano-SiOx and nano-Al2 O3 nanocomposite were prepared by ball milling treating method. Differential Scanning Calorimetry(DSC)was used to study effects of nanoparticles on curing speed of nanocomposited adhesive, and dynamic mechanical analyzer (DMA) was utilized to analyze the glass transition temperature.Results showed a increase in curing speed of nanocomposites in comparision with the neat J-27H, the curing speed of SiOx/J -27H nanocompositeis higher than Al2O3/J-27H nanocomposite. The curing speed of 6wt% SiOx/ J-27H nanocomposite is six times that of neat J-27H. Glass transition temperature measured for SiOx/ J-27H nanocomposite showed a slight increase compared to the neat J-27H.