Long-term corona behaviour and performance enhancing mechanism of SiC/epoxy nanocomposite in SF6 gas environment

Surface coating technology is an effective way to solve the interface insulation problem of DC GIS/GIL basin insulators, but the performance of the coating will change greatly, and the insulation strength will be completely lost, after long-term use in the extreme conditions of corona erosion. In this research, the multi-needle-plate electrode platform was constructed to explore the long-term use performance of Si C-doped nanocomposite exposed to corona discharge in SF6gas. Samples with a high Si C content have advantages in maintaining physical and chemical properties such as elemental composition, erosion depth, surface roughness and mass loss. The nanocomposite doped with 6 wt.% Si C has prominent surface insulation strength after long term exposure to corona, and the others are close to losing, or have completely lost,their insulating properties. Furthermore, the degradation mechanism of physicochemical properties of composite exposed to corona discharge was investigated with the proposed Reax FF MD model of energetic particles from SF6decomposition bombarding the epoxy surface. The reaction process of SF particles and F particles with the cross-linked epoxy resin, and the Si C nanoparticles providing shelter to the surrounding polymer and mitigating their suffering direct bombardment, have been established. The damage propagation depth, mass loss and surface roughness change of nanocomposite material bombarded by SF6decomposition products is reproduced in this simulation. Finally, the deterioration mechanism of insulation properties for the Si C-doped composite was elucidated with DFT analysis. The band gap of the molecule containing S drops directly from the initial 7.785 e V to 1.875 e V, which causes the deterioration of surface electric properties.

Rheological behavior of novel polyamide 6/silica nanocomposites containing epoxy resins

A novel polyamide 6/silica nanocomposite containing epoxy resins(EPA6N) was prepared via in situ polymerization using tetraethoxysilane(TEOS) as the precursor of silica.The dynamic rheological properties of pure PA6 and EPA6N at temperatures of 225 and 235 ℃ were investigated.The results of transmission electron microscopy(TEM) and atomic force microscopy(AFM) indicate that the silica particles are well dispersed in the polyamide 6 matrix on about 30 nm in diameter,which demonstrates that this method can effectively avoid agglomeration of the inorganic particles.The rheological results suggest that pure PA6 shows Newtonian behavior.However,the novel EPA6N exhibits a solid-like rheological behavior,which is due to the small size,large surface of silica particles and the stronger polyamide 6-silica chemical bond formed through the reactions of epoxy resins with end groups of PA6 molecular chains.The EPA6N also exhibits higher melt viscosity,storage modulus and loss modulus than those of pure PA6.

Influences of POSS-E-GO Content on Mechanical Properties of Bio-based Epoxy/DOPO-POSS Nanocomposites

The bio-based epoxy nanocomposite(GAER/DOPO-POSS)was prepared from gallic epoxy resin(GAER)and polyhedral oligomeric silsesquioxane(which containing 9,10-dihydrogen-9-oxo-10-phosphorus-phenanthrene-10-oxide groups,called DOPO-POSS).The polyhedral oligomeric silsesquioxane containing epoxy groups(E-POSS)was grafted onto aminated graphene oxide(E-GO),then the novel POSS-E-GO was obtained.The POSS-E-GO was used as modifier for GAER/DOPO-POSS nanocomposite.The influences of POSS-E-GO content on mechanical properties,dynamic mechanical properties and thermal stability of GAER/DOPO-POSS nanocomposites were determined.The experimental results show that POSS-E-GO can significantly improve the toughness of the GAER/DOPO-POSS nanocomposite.When 0.5wt% POSS-E-GO was added in GAER/DOPO-POSS nanocomposite,the impact strength of the nanocomposite was 4.74 kJ/m^(2) higher than that in the absence of POSS-E-GO,meantime the initial thermal degradation temperature was 277℃.

Re-Assembly of Archaeological Massive Limestones Using Epoxy Resin Modified with Nanomaterials—Part 1: Experimental

Massive limestones were used in construction of ancient Egyptian tombs, temples, obelisks and other sculptures. These stones are always exposed to physico-mechanical deterioration and destructive forces, leading to partial or total collapse. The task of reassembling this type of artifacts represents a big challenge for the conservators. Recently, the researchers are turning to new technologies to improve the properties of traditional adhesive materials and techniques used in re-assembly of broken massive stones. The epoxy resins are used extensively in stone conservation and re-assembly of broken stones because of their outstanding mechanical properties. The adding of nanoparticles to polymeric adhesives at low percentages may lead to substantial improvements of their mechanical performances in structural joints and massive objects. The aim of this study is to evaluate the effectiveness of montmorillonite clay, calcium carbonate, and silicon dioxide nanoparticles for enhancing the performances of epoxy adhesives used in re-assembly of archaeological massive limestones. Scanning electron microscopy (SEM) was employed in order to investigate the morphology of the prepared nanocomposites, and the distribution of nanoparticles inside the composites. Artificial aging, tensile, compressive, and elongation strength tests were used to evaluate the efficiency of epoxy-nanocomposites. The results showed that the epoxy-clay nanocomposites exhibited superior tensile, compressive, and elongation strength, in addition to improving the mechanical properties of stone joints.

纳米颗粒填充玻璃纤维增强环氧树脂复合材料的力学性能

为探究纳米颗粒[纳米氧化铁(NFe)、纳米二氧化硅(NS)、多壁碳纳米管(MWCNT)]填充玻璃纤维增强环氧树脂复合材料(GFRP)的力学性能,对纳米颗粒质量分数分别为0.1%、0.2%、0.5%、1.0%的纳米颗粒/GFRP材料开展了拉伸、压缩、弯曲及冲击力学性能试验,并结合扫描电镜(SEM)分析了纳米颗粒的种类及质量分数对试件力学性能的影响规律。结果表明,随着纳米颗粒质量分数的增加,试件拉伸强度均先增大后降低,纳米颗粒的良好分散性及与树脂间的黏聚力能够提升试件的拉伸强度,但过量纳米颗粒的掺入会形成积聚现象,使得试件拉伸强度降低。相较于GFRP试件,掺入纳米颗粒的质量分数为0.1%、0.2%、0.5%和1.0%时,MWCNT/GFRP抗压强度的增幅分别为25.31%、36.04%、26.84%和27.25%,弯曲强度的增幅分别为58.74%、63.21%、40.89%及43.11%,纳米颗粒的掺入使得试件抗压强度、弯曲强度、冲击强度均得到改善,颗粒种类及质量分数的不同使得试件力学性能提升效果存在差异。SEM试验结果表明,外荷载作用下纤维出现断裂、分层现象,纤维与纳米颗粒间存在的摩擦效应增强其力学性能,颗粒的积聚使得试件力学性能降低。

咪唑啉季铵盐缓蚀剂改性蒙脱土/水性环氧纳米复合涂料

以油酸、二乙烯三胺和氯化苄为原料,合成了油酸基咪唑啉季铵盐缓蚀剂。通过FTIR、^(1)HNMR对其结构进行了表征,并离子交换至钠基蒙脱土(DK0)层间,制备了缓蚀剂改性蒙脱土(QACDK0)。通过XRD、TGA和UV-Vis对其结构、组成及层间缓蚀剂释放性能进行了表征。结果表明,咪唑啉季铵盐缓蚀剂约占QACDK0质量的38.96%,并将蒙脱土层间距由1.28 nm(DK0)扩大至3.98 nm(QACDK0)。利用DLS及Zeta电位对添加有QACDK0的水性环氧树脂进行了稳定性测试,其Zeta电位为–27.8 mV,具有较高的稳定性。电化学阻抗谱(EIS)测试表明,在腐蚀介质中浸泡30 d后,基于QACDK0制备的清漆漆膜仍具有2.29×10^(8)Ω·cm^(2)的高阻抗,表明涂层具有较好的耐腐蚀性。并且在耐中性盐雾测试中,QACDK0对应的防腐色漆耐盐雾时间最长,验证了该涂层具有良好的耐盐雾性能。

Epoxy/Clay有机-无机纳米复合材料

通过插层复合的方法可以制备环氧树脂 /粘土纳米复合材料 ,大幅度提高材料的机械力学性能。制备中 ,插层剂的选择和使用是关键 ,应加强插层剂的合成、筛选及插层工艺以及粘土层内层外插层剂、固化剂、单体、粘土片层之间相互作用即插层机理的研究。此外 ,环氧树脂 /粘土纳米复合体系最佳固化条件 (树脂 /固化剂比例 ,固化时间等 )

Epoxy resin nanocomposites reinforced with ionized liquid stabilized carbon nanotubes

Epoxy resin nanocomposites reinforced with three different ionic liquid functionalized carbon nanotubes(f-CNTs)were fabricated by an in situ polymerization method.The influence of the anions on the curing process was studied through differential scanning calorimetry(DSC)and normalized Fourier transform infrared(FTIR)spectroscopy.The composition of the nanocomposites was analyzed by X-ray photoelectron spectroscopy.Two different mechanisms are proposed to explain the curing process of the neat epoxy and its composites.The electric conductivity and mechanical properties of the nanocomposites are also reported.The tensile strength was increased dramatically due to the insertion of f-CNTs.Scanning electron microsopy fracture surface analysis indicates a strong interfacial bonding between the carbon nanotubes and the polymer matrix.

ZnS/Bacterial Cellulose/Epoxy Resin(ZnS/BC/E56) Nanocomposites with Good Transparency and Flexibility

ZnS/bacterial cellulose/epoxy resin （ZnS/BC/E56） nanocomposites with good transparency and flexibil-ity were prepared and characterized. When the precursor Zn^2＋ concentrations were not more than I wt%, the size of the introduced ZnS nanoparticles was smaller than 50 nm and the distribution was homo-geneous within the composites. Under the condition, outstanding transmittance more than 70g in the visible light was obtained. By incorporation of ZnS nanoparticles with excellent thermo-optic stability to the composites, the thermo-optic coefficient was obviously increased from -361 × 10^-6 to -310 × 10^-6K^-1. The good flexibility, optical and mechanical properties endow the nanocomposites potential applica- tions in the flexible optoelectronic materials.

插层聚合制备粘土/环氧树脂纳米复合材料过程中粘土剥离行为的研究

用ＸＲＤ、ＤＳＣ 等手段研究了有机蒙脱土在环氧树脂中的插层与剥离行为，证明环氧树脂容易插层到粘土片层间，形成稳定的插层混合物，加入胺固化剂固化后，粘土被剥离而得到剥离型纳米复合材料，剥离程度与所采用的固化温度关系不大，主要取决于固化程度，全部剥离的时间与环氧树脂凝胶的时间接近．

环氧/粘土纳米复合材料的形成机理与性能

粘土 /聚合物纳米复合材料由于具有优良的物理力学性能和特殊功能而倍受关注。实验证明 ,粘土也很容易被环氧树脂插层 ,并在固化过程中剥离 ,得到纳米复合材料。本文重点综述了粘土 /环氧纳米复合材料的形成机理 ,结构形态和力学性能 ,并对该类材料的应用前景进行了展望。

有机蛭石/酚醛树脂熔融插层纳米复合材料的研究

用十六烷基三甲基溴化铵对膨胀蛭石进行了有机化处理,并用熔融法制备了有机蛭石/酚醛树脂插层纳米复合材料。通过XRD,AFM,TGA测试分析了所制备的复合材料的结构与热性能。结果表明:酚醛树脂能插层于蛭石片层中,制得的蛭石/酚醛树脂插层纳米复合材料的耐热性有了很大程度的提高。

环氧树脂/粘土纳米复合材料的研究

用原位插层聚合法制备环氧树脂 /粘土纳米复合材料。用X衍射 (XRD)、红外光谱 (FTIR)、示差扫描量热法 (DSC)、扫描电镜 (SEM)对有机化蒙脱土 (OMMT)和环氧树脂 /粘土纳米复合材料进行测试与表征。结果表明 ,与纯环氧树脂固化物相比 ,环氧树脂 /粘土纳米复合材料的力学。

环氧树脂/蒙脱土纳米复合改性的研究

采用熔融插层法制备了综合力学性能优异的环氧树脂 /蒙脱土复合体系 ,其剪切强度高于 EP/ PA基体 2倍以上 ,并具有良好的耐水及其它介质的性能。经 TGA分析 ,环氧树脂 /蒙脱土复合材料的热稳定性能略有提高。

一种促进粘土在环氧树脂中剥离的方法研究

使用对环氧树脂的固化反应有促进作用的有机阳离子对粘土进行有机化处理 ,得到的有机土与环氧树脂混合后 ,尽管其层间距较小 ,层间容纳的环氧树脂较少 ,但由于催化作用使层间环氧树脂固化较快 ,结果在环氧的固化过程中粘土更易剥离 ,从而得到粘土剥离程度较高的环氧树脂 /粘土纳米复合材料。这一研究为制备粘土剥离程度更高、性能更好的环氧 /粘土纳米复合材料提供了有效的方法。

无机纳米粒子/环氧树脂基复合材料的研究现状

系统地综述了近年来纳米改性环氧树脂基复合材料的研究现状。介绍了环氧树脂基纳米复合材料的制备方法和无机纳米粒子的表面修饰方法 ,分析了环氧树脂基纳米复合材料的形成机理和固化反应动力学 。

纳米碳管/环氧树脂纳米复合材料的研究

采用熔融混合法合成了不同纳米碳管含量的纳米碳管/环氧树脂复合材料,测试了弯曲性能、冲击强度,并利用扫描电镜(TEM)对产物进行了表征,同时,针对纳米碳管对环氧树脂电学性能的影响做了初步研究。结果表明,当纳米碳管含量为0.05%时,纳米碳管/环氧树脂复合材料的冲击强度、弯曲强度最高,弯曲强度提高100%,弯曲模量提高41%,冲击强度提高4倍,纳米碳管在环氧树脂基体中呈单根分散,纳米碳管使环氧树脂的体积电阻下降,导电性增加。

剥离型环氧树脂/蒙脱土纳米复合材料研究

采用阳离子交换的方法对蒙脱土进行了有机化处理 ,使蒙脱土由亲水性变成亲油性 ,并且使其层间距由原来的 1.2nm扩大到 2 .2nm。采用X 射线衍射仪研究了有机蒙脱土在环氧树脂中的剥离行为 ,制备了环氧树脂 蒙脱土纳米复合材料并测试了其性能。实验结果表明 ,环氧树脂与有机蒙脱土的相容性好 ,蒙脱土在环氧树脂中完全剥离 ;环氧树脂 蒙脱土纳米复合材料的力学性能。

粘土/环氧树脂纳米复合材料的性能研究

利用改性蒙脱土制备粘土 /环氧树脂纳米复合材料 ,并对材料的结构和性能进行测试和表征。结果表明 ,少量蒙脱土的加入可以较大地提高材料的力学性能和耐热性能 ,对环氧树脂同时起到了增韧增强的作用。

低填料比石墨烯/环氧树脂复合材料非线性电导机理的实验研究

为研究石墨烯导电填料的加入对环氧材料电导机理的影响,制备了不同填料质量比下石墨烯/环氧树脂复合材料。通过测量得到该复合体系的渗流阈值为质量分数1.35%,选择了石墨烯填料质量分数为0.3%、远低于渗流阈值的复合材料进行研究。利用高温高场强电导电流测试系统,测量了纯环氧材料和石墨烯/环氧复合材料在50、80和100℃下和0.24~14.4 k V/mm场强下的极化电流曲线。研究结果表明：直流电压作用下,两种材料的极化电流衰减速率均随场强和温度的增加而增大。随着场强的增大,两种材料的电导机理均发生了从欧姆电导到空间电荷限制电流理论（SCLC）为主导的转变,且这种转变电导电流场强阈值（Ethi）随温度的升高而降低。石墨烯填料的加入使环氧材料电导电流密度活化能增大,且活化能随着场强的增加逐渐降低,石墨烯/环氧复合材料在高场强区的电导机理受SCLC和隧道效应共同影响。