纳米二氧化硅补强可生物降解聚酯弹性体的制备与性能

通过原位聚合和界面改性,制备出SiO2含量0phr～20phr(质量份数)的纳米SiO2/聚(癸二酸-丙三醇-柠檬酸)酯复合材料,并研究了其结构与性能。力学性能测试结果表明,改性纳米SiO2对弹性体表现出了优异的补强效果,拉伸强度可从0.9MPa提高到5.3MPa;扫描电镜(SEM)和透射电镜(TEM)表明,SiO2以纳米网络状态分散于基体中,与基体间界面结合良好;X射线衍射(XRD)谱图从分子短程相互作用的角度反映出SiO2的存在不利于有序结构的生成;差示扫描量热(DSC)曲线显示,随SiO2含量增加,材料的Tg向低温方向移动;降解性能测试表明,SiO2的加入有助于调节材料的降解速度。     

含叔胺结构可聚合纳米SiO2杂化粒子的制备及其光固化性能

用3-氨丙基三乙氧基硅烷对纳米SiO2行表面修饰,并与三羟甲基丙烷三丙烯酸酯进行Micheal 加成反应制备含叔胺结构的可聚合纳米SiO2杂化粒子.FT-IR和TGA分析表明:含叔胺结构的有机化合物接枝到了纳米SiO2表面,接枝率为22.6%.将其应用于光固化涂料中,纳米SiO2杂化粒子在涂料中分散均匀,可克服涂料光固...     

Nanosilica/PMMA composites obtained by the modification of silica nanoparticles in a supercritical carbon dioxide–ethanol mixture

Nanosilica/poly(methyl methacrylate) (PMMA) composites are used to improve the mechanical properties of neat PMMA polymer. In order to obtain superior mechanical properties, it is essential to achieve good bonding between the SiO₂ nanoparticles and the PMMA matrix, which is typically achieved by coating silica nanoparticles with silane coupling agents. In this study, conventional and supercritical coating methods were investigated together with their influence on the mechanical properties of the obtained nanosilica/PMMA composites. The results indicate advantageous properties of nanosilica modified in the supercritical phase of carbon dioxide and ethanol in terms of particle size distribution, amount of coated silane, and dispersion in the PMMA matrix. Careful dispersion of the starting silica nanoparticles in ethanol at low temperatures in order to obtain a nanosilica sol plays an important role in deagglomeration, dispersion, and the coating process. The resulting nanosilica/PMMA composite containing nanoparticles obtained by supercritical processing of the nanosilica sol showed an increase in hardness by 44.6% and elastic modulus by 25.7% relative to neat PMMA, as determined using the nanoindentation technique. The dynamic mechanical analysis reveals that addition of nanoparticles as nanosilica sol and nanosilica gel enhances composite storage modulus by about 54.3 and 46.5% at 40 °C. At the same temperature, incorporation of modified silica nanoparticles with conventional method leads to an increase of 15.9% for the storage modulus, probably due to a large silica particle size and lower silane content in this sample.     

Effects of colloidal nanosilica on the rheological properties of epoxy resins filled with organoclay

The rheological properties of epoxy resins filled with organoclay and colloidal nanosilica were investigated by employing a parallel plate rheometer in flow mode at 25 degrees C. Shear thickening and shear thinning behaviors were observed in the epoxy resins filled with a mixture of organoclay and colloidal nanosilica. Minima were observed in the relaxation time of the systems consisting of epoxy resins filled with organoclay and colloidal silica as the content of colloidal nanosilica was increased. It seems that the colloidal nanosilica increased the mobility of the filled epoxy resins and reduced the interactions between the silicate layers in the systems.     

Improved tensile properties of basalt fibre reinforced polymer composites using silica nanoparticles

In this study, the effect of silica nanoparticles as the reinforcing filler on the tensile response of basalt fibre reinforced polymer (BFRP) composite was investigated. A 40 wt.% nanosilica gel in epoxy was used to prepare a series of nanocomposites with 5 wt.%, 15 wt.% and 25 wt.% nanosilica. Static uniaxial tensile tests were conducted on the basalt fibre reinforced polymer composite to investigate the stress‐strain response of the unmodified and nanomodified composites. It was found that the incorporation of silica nanoparticles with high specific surface area improved the tensile properties of the basalt fibre reinforced polymer composite. The addition of silica nanoparticles in the composite shows significant improvement in tensile modulus with 6 %, 14 % and 19 % for 5 wt.%, 15 wt.% and 25 wt.% nanosilica content, respectively. The higher content of silica nanoparticles in the matrix increased the stiffness of the material as well as the strength of the basalt fibre reinforced polymer composite without reducing the failure strain.     

Reinforcement of polysiloxane with superhydrophobic nanosilica

We systemically report on a new method for producing reinforced poly(dimethylsiloxane) (PDMS) with superhydrophobic nanosilica. Firstly, we rationally designed to synthesize a series of well-dispersed hydrophobic nanosilica by using hexadecyltrimethoxysilane (HDTMS) as the treatment agent. Fourier transforms infrared (FT-IR) spectrum, thermo-gravimetric analysis (TGA), and contact angle (CA) measurement were used to characterize the grafting degree of HDTMS grafted onto the surface of nanosilica. Subsequently, we employed these modified hydrophobic nanosilica to further reinforce PDMS. The properties of as-prepared modified nanosilica filled PDMS composites were thoroughly investigated by rheological test, scanning electron microscopy (SEM), TGA, and dynamic mechanical analysis (DMA). We have found that these as-prepared superhydrophobic nanosilica exhibit uniform dispersity in the PDMS matrix, and their composites exhibit good mechanical properties and obvious advantage on thermal stability compared with those of the pure silica filled PDMS composites.     

透明超疏水聚乙烯薄膜的制备及性能分析

目的研究包装透明超疏水聚乙烯(PE)薄膜的制备方法及其性能。方法以纳米二氧化硅和无水乙醇为原料,将纳米二氧化硅溶于无水乙醇制得二氧化硅半透明溶液,采用浸渍提拉法将PE膜在二氧化硅溶液中浸泡数分钟后提拉取出并自然干燥,然后用扫描电子显微镜、接触角测量仪、透光率雾度测定仪测量膜表面的性能,并进行研究分析,用污水浸泡样品数天后测量其抗污性。结果成功制备了透明超疏水PE薄膜,其表面与水的接触角高达(171±2)°,滚动角低至1°。当纳米二氧化硅的质量浓度为10 mg/mL时,其薄膜表面表现出了优异的透明性、防水性和抗污染自清洁性。结论采用简易方法制备了透明超疏水聚乙烯塑料薄膜,提高了聚乙烯膜超疏水自清洁的性能,大大增强了聚乙烯膜在包装领域的应用前景。     

Characterization of surface accumulation and release of nanosilica during irradiation of polymer nanocomposites by ultraviolet light

Polymer nanocomposites are increasingly used in applications that are subjected to harsh environments. Owing to polymer's susceptibility to photodegradation, nanofillers in a polymer nanocomposite may be released into the environments during the composite's life cycle. Such release potentially poses an environmental health and safety problem and may hinder commercialization of these advanced materials. This study investigated the fate and release of nanosilica from epoxy/nanosilica composites. Specially-designed holders containing nanocomposite specimens were irradiated with UV light in a well-controlled environmental chamber. UV irradiated samples were removed for measurements of polymer chemical degradation, mass loss, surface morphology, nanosilica accumulation on the composite surface, and nanosilica release. Epoxy matrix underwent rapid photodegradation, resulting in substantial accumulation of silica nanofillers on the composite surface and also release from the composite. A conceptual model for surface accumulation and release of nanosilica during UV irradiation of epoxy nanocomposites is presented.     

偶联剂对纳米SiO2／树脂复合材料显微形貌及性能的影响

采用不同的偶联剂KH550、KH560和KH570对纳米SiO2进行表面处理,然后将其与拼混树脂制成复合材料。利用TEM、FT-IR和TGA等分析测试手段对不同偶联剂处理的纳米SiO2进行表征和分析,同时对复合材料的显微形貌及耐热性能进行一定的考察。结果表明,SiO2与三种偶联剂均形成化学键合。相比之下,用KH560处理的SiO2在基体树脂中分散性较好,复合材料耐热性较高。     

纳米SiO2/聚氨酯杂化材料的研究进展

综述了近10年纳米SiO2改性聚氨酯的研究进展,主要介绍了由3种方法制备的纳米SiO2/聚氨酯杂化体的形态结构及杂化体中SiO2与聚氨酯分子的相互作用力,并讨论了引入SiO2对聚氨酯体系的力学性能、热学性能、光学性能、耐磨损性、耐刮伤性能的影响.     

Ultrasound-assisted synthesis of colloidal nanosilica from silica fume: Effect of sonication time on the properties of product

Current methods of colloidal nanosilica production are relatively energy-intensive and in some cases not environmentally friendly and therefore essential needs are felt to develop new low cost environmentally friendly methods. This study is devoted to the synthesis and characterization of colloidal silica nanoparticles prepared from silica fume using ultrasound. Colloidal nanosilica has been synthesized via dissolution-precipitation process followed by applying ultrasonic waves with the power and frequency of 30 W and 20 kHz, respectively. The produced colloidal nanosilica was characterized via dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and measurements of its zeta potential and specific surface area. DLS results show that minimum particle size, average diameter and maximum particle size of the produced colloidal nanosilica decrease sharply from 28.21, 54.92 and 164.20 nm to 18.17, 38.72 and 141.80 nm, respectively, during the first 15 s of sonication. No significant changes have been observed in applying continued sonication up to 60 min. Measurements of zeta potential confirmed a relatively good stability of the produced colloidal nanosilica.     

Nanosilica-decorated sponges for efficient oil/water separation: role of nanoparticle’s type and concentration

Oil absorption by porous materials is currently regarded as a very efficient method for water purification and oil spill cleanup. Simultaneous induction of superhydrophobic and superoleophilic properties into porous materials was conducted in this study via surface decoration of sponges by nanosilica. The main aim was to investigate the effects of nanosilica concentration on the final wetting behavior of the sponges. To this end, the sponges were treated with both modified and unmodified nanosilica particles through a simple dipping process. It was found that only a moderate concentration of nanoparticles (2 vol%) causes the sponges surface to be uniformly decorated with silica. Based on X-ray photoelectron spectroscopy results, it was postulated that surface energy of the sponges was a more influential factor in the final wetting behavior as compared with the surface roughness. The values of oil absorption capacity were varied in the range of 51–72 g/g (gram of oil per gram of sponge) for the superhydrophobic sample using four different oils and organic liquids. It was concluded that the prepared sponges definitely possess promising potential in the separation of oil/water mixtures provided that an optimum concentration of nanosilica with proper surface modification is used.     

Characterization of transverse tensile, interlaminar shear and interlaminate fracture in CF/EP laminates with 10 wt% and 20 wt% silica nanoparticles in matrix resins

The transverse tensile properties, interlaminar shear strength (ILSS) and mode I and mode II interlaminar fracture toughness of carbon fibre/epoxy (CF/EP) laminates with 10 wt% and 20 wt% silica nanoparticles in matrix were investigated, and the influences of silica nanoparticle on those properties of CF/EP laminates were characterized. The transverse tensile properties and mode I interlaminar fracture toughness (G_IC) increased with an increase in nanosilica concentration in the matrix resins. However, ILSS and the mode II interlaminar fracture toughness (G_IIC) decreased with increasing nanosilica concentration, especially for the higher nanosilica concentration (20 wt%). The reduced G_IIC value is attributed to two main competing mechanisms; one is the formation of zipper-like pattern associated with matrix microcracks aligned 45° ahead of the crack tip, while the other is the shear failure of matrix. The ratio of G_IIC/G_IC decreased with the concentration of silica nanoparticles, comparable with similar CF/EP laminates with dispersed CNTs in matrix. Fractographic studies showed that interfacial failure between carbon fibre and epoxy resin occurred in the neat epoxy laminate, whereas a combination of interfacial failure and matrix failure occurred in the nanosilica-modified epoxy laminates, especially those with a higher nanosilica concentration (20 wt%).     

Controlling foam morphology of polystyrene via surface chemistry,size and concentration of nanosilica particles

Controlling cell morphologies of polymeric foams is an important part of controlling foam properties. In this study, the effects of particle size, particle content, and particle surface chemistry on cell nucleation in nanosilica/polystyrene (PS) composites are investigated. A theoretical hypothesis on the effect of nanoparticle size on cell nucleation in PS matrix foam was examined. The surface chemistry of nanosilica particles was studied by modifying them with Vinyltriethoxysilane (VTES) silane coupling agent. The microcellular porous materials of neat and composite PS were prepared by batch foaming technique (pressure quench) using supercritical carbon dioxide (ScCO₂) as a blowing agent. It was found that the size of the pores decreases and the cell density increases with the decrease in nanosilica size and the increase of silica loading. It was also observed that the surface treatment of the nanosilica particles have substantial effect on the decrease of the cell size and the increase of the cell density.     

纳米SiO2与粉煤灰协同改性水泥基材料性能研究

通过调整纳米SiO_2与粉煤灰的比例,研究了两者协同作用对水泥基材料性能的影响。结果表明,纳米SiO_2(NS)和粉煤灰协同作用效果优于NS单一掺加,3%(质量分数,下同)纳米SiO_2和不大于30%的粉煤灰同时掺加可以补偿粉煤灰引起的早期强度降低,且砂浆28d抗压强度不降低。随着NS掺量增加水泥基材料的干燥收缩增大,粉煤灰可以改善纳米SiO_2对干燥收缩的不利影响。随着NS掺量的增加,试件的抗冻性和抗氯离子渗透性能均得到提升,掺加3%NS与30%粉煤灰使水泥基材料达到最佳耐久性能。NS可以缩短水泥水化诱导期,加速水泥水化进程,且使胶凝体系总放热量增加。在水泥粉煤灰体系中掺入NS后,非蒸发水含量在早期明显增多,但在后期增长缓慢。     

Development of polyimide–nanosilica filled EPDM based light rocket motor insulator compound: Influence of polyimide–nanosilica loading on thermal,ablation, and mechanical properties

Thermal protection materials are necessary to protect structural components of launch vehicles during lift-off of launching system. The present study deals with the development of a novel thermally protected light rocket motor insulator compound (RMIC) of polyimide–silica filled EPDM nanocomposites. The insulation compound prepared for the studies comprised of aromatic polyimide and nanosilica particles. The addition of these materials in rocket insulator compound enhanced the multifunctional thermal and insulation characteristics. EPDM when grafted with maleic anhydride, contributed polarity in the non-polar EPDM matrix. Nanosilica contributes specifically better erosion resistance. SEM and TEM micrograph of EPDM nanocomposites exhibits good dispersion of nanosilica in polyimide–EPDM matrix. Nanocomposite formation was characterised by FTIR. Density, co-efficient of thermal expansion, thermal conductivity, ablation rate, specific heat, maximum thermal degradation, char yield and mechanical properties of the RMIC have been measured. This developmental study may find wide scope for commercial exploitation.     

纳米SiO2添加量对紫外光固化涂料涂层性能的影响

将纳米SiO2加入紫外光固化涂料,可以改善其涂层性能。制备了UV固化环氧丙烯酸酯/纳米SiO2复合涂料涂层,对其硬度、附着力、耐腐蚀性能及热稳定性等性能进行了研究,找出了纳米SiO2对涂层性能的影响规律。结果表明:涂层的硬度及附着力先随纳米SiO2添加量的增加而提高,添加量为3.0%时,涂层附着力达1级;添加量为4.0%时,涂层铅笔硬度达5H;添加量继续增大,涂层的硬度及附着力均下降;纳米SiO2的加入能够提高涂层的热稳定性和耐腐蚀性能,但添加量过多涂层耐腐蚀性能反而下降。     

纳米二氧化硅影响水泥基材料流动性的研究综述

纳米二氧化硅比表面积大、粒径小等特点有助于其发挥火山灰活性、晶核效应和填充效应,能够促进水泥水化,有效改善水泥基材料内部结构。在所有改性水泥基材料的纳米材料中纳米二氧化硅应用最为广泛,已经成为许多研究者探究的热点,但还未见关于纳米二氧化硅影响水泥基材料流动性综述的报道。本文主要综述了粉体和溶胶两种纳米二氧化硅对水泥基材料流动性的影响、存在的问题及改性纳米二氧化硅对水泥基材料性能的影响,为今后进一步研究纳米二氧化硅改性水泥基材料提供依据。     

Poly(vinyl alcohol)/silica hybrid nanocomposites by sol-gel technique: Synthesis and properties

Poly(vinyl alcohol)/silica organic inorganic hybrid composites were prepared by using sol-gel technique. Tetraethoxysilane was used as the precursor for silica. The reaction was carried out in an aqueous medium having a pH of 1.5 with concentrated hydrochloric acid, used as the catalyst. All the composites were optically clear. Interaction at organic-inorganic interfaces due to hydrogen bonds was speculated from infrared spectroscopic analysis of the hybrid composites. Transmission electron microscopic studies revealed the existence of silica nanoparticles, uniformly dispersed in the organic matrix, which were found to grow in size with increase in tetraethoxysilane loading in the composites. Uniform dispersion of silica particles within the hybrid nanocomposites was also supported from the energy dispersive X-ray mapping of silicon. Dynamic mechanical properties exhibited substantial mechanical reinforcements due to the dispersion of nanosilica particles in the matrix. The results were further supported by significant improvements in the Young's modulus and the tensile strengths of the samples. All the hybrid composites demonstrated excellent water resistance.     

光固化水性聚氨酯/二氧化硅纳米复合膜的微结构与膜性能

在光固化水性聚氨酯乳液合成中原位引入纳米二氧化硅水溶胶制备复合乳液及复合膜,研究了二氧化硅粒径、表面化学特性对复合膜微观结构和性能的影响。透射电镜(TEM)和原子力显微镜(AFM)分析表明,表面有机改性二氧化硅很好分散在聚氨酯基体中,而酸性、碱性硅溶胶在聚氨酯基体中发生不同程度团聚和粘连,且不同粒径、表面化学特性的二氧化硅对纳米复合涂层表面形貌有较大影响;动态力学性能(DMA)分析表明,不同纳米二氧化硅引入对聚氨酯软硬段相分离产生较大影响,可不同程度提高复合膜的储能模量。