SiO2/环氧树脂基纳米复合材料的室温和低温力学性能

利用溶胶-凝胶法制备了SiO₂/环氧树脂基复合材料,研究了材料的室温与低温(77 K)下的力学性能。结果表明,适量SiO₂的引入提高了室温与低温下材料的拉伸强度、断裂伸长率和冲击强度,即SiO₂含量在2%时可同时起到增强、增韧作用。采用扫描电镜(SEM)和透射电镜 (TEM)分别对复合材料的断口形貌和高温焚烧后残留物纳米颗粒进行了观察。还利用动态力学分析(DMA)研究了二氧化硅的引入对复合材料的影响。      

Improvement of tensile properties and toughness of an epoxy resin by nanozirconium-dioxide reinforcement

Zirconium dioxide (ZrO₂) nanoparticles were systematically added as reinforcement to a diglycidyl ether of bisphenol A (DGEBA)-based epoxy resin. A series of composites with varying amounts of nanoparticles was prepared and their morphology and mechanical properties were studied. The obtained nanocomposites were characterized by tensile tests, dynamic mechanical thermal analysis, and fracture toughness (K_IC) investigations; by standardized methods, to define the influence of the nanoparticle content on their mechanical and thermal properties. The morphological analysis of the composites shows that nanoparticles form small clusters, which are uniformly distributed into the matrix bulk. The tensile modulus (E) and the K_IC of the epoxy matrix increase at rising zirconia content. Improvements of more than 37% on modulus and 100% on K_IC were reached by the nanocomposite containing 10 vol.-% ZrO₂ with respect to the neat epoxy (E_o = 3.1 GPa, K_ICo = 0.74 MPam^0.5). The presence of nanoparticles produces also an increment on glass transition temperature (T _g). The epoxy resin added with 8 vol.-% ZrO₂ records a T _g approximately 8% higher than the unmodified matrix (T _go = 100.3 °C).     

The role of epoxy matrix occlusions within BaTiO3 nanoparticles on the dielectric properties of functionalized BaTiO3/epoxy nanocomposites

In this work, the effects of controlled nanoparticles aggregations of barium titanate (BaTiO₃) on the dielectric properties of epoxy nanocomposites are investigated in detail with respect to different experimental parameters like frequency, ceramic content and temperature. Dispersing silanized BaTiO₃ nanopowder under ultrasonic and stir, nanocomposites of epoxy-amine matrix with different morphologies are obtained. The nanoparticles silane functionalization containing amine end groups effectively improve the compatibility of the nano-BaTiO₃ and the epoxy matrix. Storage modulus, glass transition temperature, tensile and flexural properties of nanocomposites and dielectric properties are increased until 10% by weight of nano-BaTiO₃ loading, well dispersed in the matrix. Above 10 wt.% of nano-BaTiO₃, scanning electronic microscopy and thermal analysis showed that agglomeration of nanoparticles occurs. Rheological and mechanical nanocomposites properties were evaluated and matrix occlusion behaviors were identified. In light of the specific behavior of the occluded polymer, the dielectric properties, especially dielectric loss are discussed.     

Preparation and characterization of epoxy/γ-aluminum oxide nanocomposites

Epoxy/γ-Al₂O₃ nanocomposites were prepared with a homogenizer and followed by a stepwise thermal curing process in this study. The dispersion of γ-Al₂O₃ nanoparticles was examined with a transmission electron microscopy (TEM). Meanwhile, the effects of γ-Al₂O₃ nanoparticles on thermal, dynamic mechanical and tensile properties of epoxy/γ-Al₂O₃ nanocomposites were also investigated and discussed. When the γ-Al₂O₃ content was increased from 1phr to 5phr, results revealed that γ-Al₂O₃ nanoparticles were effective to enhance both the stiffness and toughness of epoxy resin. Meanwhile, the maximum properties of glass transition temperature (T_g), T_d5%, storage modulus, tensile modulus, and elongation at break were observed in the epoxy/5phr γ-Al₂O₃ nanocomposite.     

Quantitation of the reinforcement effect of silica nanoparticles in epoxy resins used in liquid composite moulding processes

Epoxy–silica nanocomposites are investigated for their suitability as a new type of matrix for fibre-reinforced polymers (FRP) using injection technology (LCM). The key focus is the determination of the processing characteristics of the nanocomposites. The silica nanoparticle content varies between 0 and 25 wt% for the high performance epoxy resin. Photon Cross Correlation Spectroscopy (PCCS) and Scanning Electron Microscopy (SEM) analysis performed on the liquid and cured epoxy–silica nanocomposites indicate a nearly homogeneous distribution of the nanoscaled silica in the epoxy matrix, even at rather high weight percentages. Depending on the silica content of the composite, its stiffness, strength and toughness can be increased significantly compared with neat resin. Moreover, resin shrinkage and the thermal expansion (CTE) can be significantly reduced and the thermal conductivity increased. Concomitant the glass transition temperature remains nearly constant. The initial viscosity of the resin increases slightly depending on the nanoparticle content, while the gel-time slightly decreases. The injectability of the nanocomposite for the purpose of lamination using the LCM technology is nearly unaffected. The optimum filler content is at approx. 25 wt% silica. Epoxy–silica nanocomposites are now proven to be a new high performance polymer matrix for FRP structures manufactured by the low cost LCM techniques.     

A detailed thermal analysis of nanocomposites filled with SiO2, AlN or boehmite at varied contents and a review of selected rules of mixture

In order to investigate and compare the thermal and mechanical properties of nanocomposites filled with various nanoparticles multiple experiments have been carried out. The aim of this study was to enhance the thermal and mechanical properties of epoxy resin for fiber reinforces structures by the addition of nanoparticles. These altered properties were analyzed and reconciled with each other as well as compared to data developed from different rules of mixture. A hot curing epoxy system based on bisphenol-A (DGEBA) has been filled with different contents of silicon dioxide (SiO₂), aluminum nitride (AlN) and boehmite nanoparticles to examine the effects in the material’s thermal and mechanical behavior with variable filler materials and contents compared to the unfilled epoxy. The glass transition temperature fluctuates very little with varied filler content. The coefficient of thermal expansion can be reduced with increasing filler content. This improvement recurs also in thermal conductivity and during dynamic mechanical analysis. Several rules of mixture have been applied to be verified on the basis of varied materials and filler contents. The results did not always match the experiments. The deviations are ascribed to the influence of interphases that build up in the vicinity of the nanoparticles during the process of curing.     

Effect of various combinations of zirconia and organoclay nanoparticles on mechanical and thermal properties of an epoxy nanocomposite coating

An epoxy based nanocomposite coating containing various combinations of treated-zirconia and clay nanoparticles were prepared. Morphology and dispersion of nanoparticles within the nanocomposites were evaluated using optical microscopy, XRD and TEM analyses. Mechanical, thermal properties and corrosion resistance of nanocomposites were studied using; tensile strength measurements, DMTA and DSC analyses and salt spray test.The results showed that simultaneous use of spherical and plate-shape nanoparticles, have a positive effect on the clay exfoliation behavior in resulting nanocomposites.Mechanical properties of nanocomposites containing nano-zirconia slightly increased compared with neat-epoxy coating. Mechanical properties of nanocomposites containing various wt.% of clay or ZrO₂/clay nanoparticles slightly decreased; formation of physical barrier clay stacks, which leads to disturbing curing procedure and decreasing polymer cross-linking density, and development of nano-sized voids in the trapped regions by clay stacks. Corrosion performance of nanocomposites increased with addition of nanoparticles, due to improving barrier properties of the coating.     

The cryogenic thermal expansion and mechanical properties of plasma modified ZrW2O8 reinforced epoxy

In this article, epoxy resin reinforced by negative thermal expansion material, ZrW₂O₈, was fabricated. The surface modification of ZrW₂O₈ particles was performed via plasma enhanced chemical vapor deposition (PECVD) process. As a result, a thin film was uniformly deposited on the surfaces of the ZrW₂O₈ particles, leading to an improvement of compatibility and dispersion of ZrW₂O₈ fillers inside epoxy matrix. Moreover, the coefficients of thermal expansion (CTEs) of the composite material containing 0-40 vol.% fillers were studied under cryogenic temperatures. The results showed a significant reduction in thermal expansion with increasing ZrW₂O₈ content. The cryogenic mechanical properties of ZrW₂O₈/epoxy composites were also investigated, showing the properties were improved by adding ZrW₂O₈ to certain content. In addition, the mechanical strength and modulus of the composite were observed significantly higher at cryogenic temperature than that at room temperature because of the thermal shrink effect and the frozen epoxy matrix.     

Size reduction of WO3 nanoparticles by ultrasound irradiation and its applications in structural nanocomposites

The porous WO₃ (pore size 2–5 nm) nanoparticles were synthesized using a high intensity ultrasound irradiation of commercially available WO₃ nanoparticles (80 nm) in ethanol. The high resolution transmission electron microscopic (HRTEM) and X-ray studies indicated that the 2–5 nm uniform pores have been created in commercially available WO₃ nanoparticles without much changing the initial WO₃ nanoparticles (80 nm) sizes. The nanocomposites of WO₃/SC-15 epoxy were prepared by infusion of 1 wt.%, 2 wt.% and 3 wt.% of porous WO₃ nanoparticles into SC-15 epoxy resin by using a non-contact (Thinky) mixing technique. Finally the neat epoxy and nanocomposites were cured at room temperature for about 24 h in a plastic rectangular mold. The cured epoxy samples were removed and precisely cut into required dimensions and tested for their thermal and mechanical properties. The HRTEM and SEM studies indicated that the sonochemically modified porous WO₃ nanoparticles dispersed more uniformly over the entire volume of the epoxy (without any settlement or agglomeration) as compared to the unmodified WO₃/epoxy nanocomposites.     

Fabrication, thermal, and dielectric properties of self-passivated Al/epoxy nanocomposites

The current paper reports the effects of an epoxide-functionalized, silane surface-treated, self-passivated aluminum (Al) nanoparticles on the glass transition, morphology, thermal conductivity, dielectric properties of an epoxy composite. The surface modification of the Al nanoparticles improved the dispersion of the filler, as well as the glass transition temperature, thermal conductivity, and dielectric properties of the epoxy composites. The epoxy/Al nanocomposites showed a dielectric constant transition concentration. The dielectric constant and dissipation factor increased when the Al particle loading exceeded the critical content but gradually decreased with the frequency. The epoxy nanocomposites containing 15 % by weight Al nanoparticles have a high thermal conductivity and a high dielectric constant but a low dissipation factor. The enhancements in the thermal and dielectric properties of the epoxy nanocomposites show potential for future engineering applications.     

Photo-stabilization properties of transparent inorganic UV-filter/epoxy nanocomposites

Transparent inorganic UV-filter/epoxy nanocomposites with high photo-stabilization properties were reported in this paper. First, inorganic UV-filter ZnO, core-shell structural silica–titania (S–T) and silica–titania–silica (S–T–S) nanoparticles were synthesized. Transparent inorganic UV-filter/epoxy (ZnO/epoxy, S–T/epoxy and S–T–S/epoxy) nanocomposites were subsequently prepared from the transparent epoxy and the as-prepared nanoparticles via in situ polymerization method. Optical properties of inorganic UV-filter/epoxy nanocomposites, namely visible light transparency and UV-light shielding efficiency, were studied using an UV–Vis spectrophotometer. The photo-stabilization properties of inorganic UV-filter/epoxy nanocomposites were examined by the light-emitting diode (LED) lifetime test. The results showed that the photo-stabilization effect of inorganic UV-filter on the lifetime of LED lamp obeys the following sequence: ZnO > S–T–S > S–T. Compared with the UV LED lamps encapsulated with pure epoxy, the lifetime of UV LED lamps encapsulated with ZnO/epoxy, S–T–S/epoxy and S–T/epoxy nanocomposites has been improved by 76%, 54% and 33%, respectively.     

The reinforcing effect of graphene nanosheets on the cryogenic mechanical properties of epoxy resins

The reinforcing effect of graphene in enhancing the cryogenic tensile and impact properties of epoxy composites is examined at a weight fraction of 0.05–0.50%. The micro-structure and cryogenic mechanical properties of the graphene/epoxy composites are investigated using scanning electron microscopy, transmission electron microscopy, small-angle X-ray scattering and mechanical testing techniques. The results show that the graphene dispersion in the epoxy matrix is good at low contents while its aggregation takes place and becomes severer as its content increases. And the cryogenic tensile and impact strength at liquid nitrogen temperature (77 K) of the composites are effectively improved by the graphene addition at proper contents. The cryogenic Young’s modulus increases almost linearly with increasing the graphene content. Moreover, the results for the mechanical properties at room temperature (298 K) of the graphene/epoxy composites are also presented for the purpose of comparison.     

Cyclic fatigue crack propagation of nanoparticle modified epoxy

An experimental study on the fatigue performance of nanoparticle modified epoxy was conducted. Seven material systems were examined which were: neat epoxy (E), 6 and 12 weight percent (wt.%) silica nanoparticle modified epoxy (S6, S12), 6 and 12 wt.% rubber nanoparticle modified epoxy (R6, R12), 3 wt.% each of silica and rubber nanoparticle modified epoxy (S3R3) and 6 wt.% each of silica and rubber nanoparticle modified epoxy (S6R6). Effects of those nanoparticles on the fatigue threshold (ΔG_th and ΔK_th) and fatigue crack propagation rates (da/dN) were studied. It was found that, compared to neat epoxy (E), nanosilica (S6, S12) increased ΔG_th (and ΔK_th) but nanorubber (R6 and R12) did not. However, a synergistic effect was observed on the fatigue threshold when both silica and rubber nanoparticles were added into epoxy. All these nanoparticles, individually or conjointly, decreased da/dN with silica the most effective. Morphology of the fracture surface was examined to understand the role of nanoparticles on toughening mechanisms under cyclic loading, which depended on the applied ΔG levels.     

Incorporation of silver nanoparticles coated with mercaptosuccinic acid/poly(ethylene glycol) copolymer into epoxy for enhancement of dielectric properties

A novel route to the synthesis of polymer-coated silver nanoparticles (NPs) was developed on the basis of the reduction of Tollens' reagent using mercaptosuccinic acid/poly(ethylene glycol) (MSA/PEG) copolymer as reducing agent and stabilizer simultaneously. The average size of the polymer-coated silver NPs could be controlled in a wide range from 10 to 120 nm by changing the MSA/PEG molar ratio. These surface-coated silver NPs can be uniformly dispersed in polar solvent and a homogeneous silver NPs/acetone dispersion has been prepared. Silver–epoxy nanocomposites have been developed by incorporating these silver NPs into epoxy. The nanocomposites with silver volume content of 25% showed a more than 3000% increase in dielectric constant as compared to neat matrix and a relatively low dielectric loss below 0.05, which meets the main requirement for embedded decoupling capacitors. Moreover, thermal properties of the silver–epoxy nanocomposites were also characterized by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). The initial decomposition temperature and glass transition temperature were elevated with the increase of silver content, which exhibit great thermal stability and facilitate electrical applications requiring higher heat-resistance.     

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%).     

Thermo-mechanical properties of randomly oriented carbon/epoxy nanocomposites

The thermo-mechanical properties of epoxy-based nanocomposites based on low weight fractions (from 0.01 to 0.5 wt%) of randomly oriented single- and multi-walled carbon nanotubes were examined. Preparation methods for the nanocomposites, using two types of epoxy resins, were developed and good dispersion was generally achieved. The mechanical properties examined were the tensile Young's modulus by Dynamic Mechanical Thermal Analysis and the toughness under tensile impact using notched specimens. Moderate Young's modulus improvements of nanocomposites were observed with respect to the pure matrix material. A particularly significant enhancement of the tensile impact toughness was obtained for specific nanocomposites, using only minute nanotube weight fractions. No significant change in the glass transition temperature of SWCNT/epoxy nanocomposites was observed, compared to that of the epoxy matrix. The elastic modulus of the SWNT-based nanocomposites was found to be slightly higher than the value predicted by the Krenchel model for short-fiber composites with random orientation.     

Strength of unidirectional glass/epoxy composite with silica nanoparticle-enhanced matrix

A technique was developed to improve the strength of unidirectional composites by enhancing the matrix properties through nanoparticles infusion. A commercially available standard DGEBA epoxy with silica nanoparticles (Nanopox F 400) was used as the matrix to make fiber composites. The silica nanoparticles in Nanopox were grown in situ via a sol–gel process resulting in a concentration of 40 wt% which was later diluted to 15 wt% particle loading. TEM images showed very uniform dispersion of silica nanoparticles with a size distribution of about 20 nm. Compression test revealed a substantial improvement (40%) in elastic modulus of the modified epoxy. A modified vacuum assisted resin transfer molding process was used to fabricate unidirectional E-glass fiber reinforced silica/epoxy nanocomposites. Inclusion of silica nanoparticles dramatically increased the longitudinal compressive strength and moderately increased the longitudinal and transverse tensile strengths. A microbuckling model was used to verify the compression testing results.     

Strengthening of basalt fibers with nano-SiO2–epoxy composite coating

Coatings, which were made from pure epoxy and SiO₂ nanoparticle modified epoxy composite, respectively, were applied onto the basalt fiber rovings. The SiO₂ nanoparticles were synthesized using a sol–gel method and modified using coupling agent. Fourier transform infrared spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC) analyses indicated the formation of modified SiO₂ nanoparticles. The SiO₂ nanoparticle–epoxy composite coating gave rise to a significant increase in the tensile strength of the basalt fibers as compared with the pure epoxy coating, and also the coating endowed the basalt fiber with a promising interfacial property in the basalt fiber reinforced resin matrix composite. The coating modification was an effective way in improving the mechanical properties of basalt fibers and the properties of basalt fiber/epoxy resin composites.     

The effect of process parameters on physical and mechanical properties of commercial low density polyethylene/ORG-MMT nanocomposites

Polyethylene/organo-montmorillonite clay (org-MMT) nanocomposites were prepared utilizing PP-g-MA as a compatibilizer by melt intercalation method. In order to increase the miscibility of polyethylene (PE) with nanoparticle surface at firs, a primary masterbatch consist of compatibilizer and org-MMT was prepared then, this compound was melt intercalated with PE to synthesis the PE/org-MMT nanocomposites. In this study, the presence of commercial low density polyethylene in Nanocomposites structure and also the effect of process parameters such as: amount of nanoparticles, mixing rate and mixing time on nanocomposite structure and properties have been investigated. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that the interlayer distance of nanoparticle layers increased and a partially intercalated structure was prepared by melt intercalation method. Interaction between polyethylene chains and nanoparticle layers could be improved if the control of above parameters causes to penetrate the chains into nanoclay layers; by an optimization, this effect could improve the physical and mechanical properties. The DSC data revealed that melting temperature has slowly increased and crystalinity has lightly decreased. Consequently we can claim the thermal properties of LDPE/clay nanocomposite did not considerably change with clay content. A rise in the mechanical properties such as yield stress and modulus was observed by tension test; by addition of 5% clay content the tensile strength increased about 7%, the tensile modulus enhanced about 60% and the yield stress increased about 16% in comparison with the pure LDPE.     

Fabrication of transparent polymer-matrix nanocomposites with enhanced mechanical properties from chemically modified ZrO<Subscript>2</Subscript> nanoparticles

Optically transparent nanocomposites with enhanced mechanical properties were fabricated using stable dispersions of sub 10 nm ZrO₂ nanoparticles. The ZrO₂ dispersions were mixed with a commercially available bisphenol-A-based epoxy resin (RIMR 135i) and cured with a mixture of two amine-based curing agents (RIMH 134 and RIMH 137) after complete solvent removal. The colloidal dispersions of ZrO₂ nanoparticles, synthesized through a non-aqueous approach, were obtained through a chemical modification of the ZrO₂ nanoparticle surface, employing different organic ligands through simple mixing at room temperature. Successful binding of the ligands to the surface was studied utilizing ATR–FT-IR and thermogravimetric analysis. The homogeneous distribution of the nanoparticles within the matrix was proven by SAXS and the observed high optical transmittance for ZrO₂ contents of up to 8 wt%. Nanocomposites with a ZrO₂ content of only 2 wt% showed a significant enhancement of the mechanical properties, e.g., an increase of the tensile strength and Young’s modulus by up to 11.9 and 12.5%, respectively. Also the effect of different surface bound ligands on the mechanical properties is discussed.