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1.
Aluminum-hydroxide-covered multi-walled carbon nanotubes (A–MWCNT) were fabricated as a thermally conductive material. The thermal conductivity of A–MWCNT was estimated based on Casimir theory. The effective thermal conductivity of A–MWCNT was estimated at about ∼26 W/mK. The thermal conductivity of A–MWCNT/epoxy-terminated polydimethylsiloxane (ETDS) composite was examined as a function of A–MWCNT loading, and the results showed the maximum value at 1.5 wt% of A–MWCNT loading, above which it decreased slightly. The effective medium approximation (EMA) developed by Maxwell–Garnett (M–G) was used to analyze the thermal conducting behavior of the composite. The experimental results showed negative deviation from the expected thermal conductivity, ke, beyond 1.5 wt% of A–MWCNT loading, because the composites containing A–MWCNT were strongly affected by interfacial resistance. The interfacial resistance value calculated from M–G approximation increased when filler loading was higher than 1.5 wt% because of the folded and partially agglomerated A–MWCNT along with insufficient interfacial interactions. 相似文献
2.
In this study, the mechanical and thermal properties of epoxy composites using two different forms of carbon nanotubes (powder and masterbatch) were investigated. Composites were prepared by loading the surface-modified CNT powder and/or CNT masterbatch into either ductile or brittle epoxy matrices. The results show that 3 wt.% CNT masterbatch enhances Young’s modulus by 20%, tensile strength by 30%, flexural strength by 15%, and 21.1 °C increment in the glass transition temperature (by 34%) of ductile epoxy matrix. From scanning electron microscopy images, it was observed that the CNT masterbatch was uniformly distributed indicating the pre-dispersed CNTs in the masterbatch allow an easier path for preparation of CNT-epoxy composites with reduced agglomeration of CNTs. These results demonstrate a good CNT dispersion and ductility of epoxy matrix play a key role to achieve high performance CNT-epoxy composites. 相似文献
3.
Composite laminates, made of glass/epoxy using compression molding technique, were subjected to impact loading. The ballistic limit and energy absorption capacity of the laminates were obtained. Experiments were carried out to study the effect of fiber orientation and thicknesses on ballistic limit and energy absorption of the laminates, by using a rigid conical bullet having 9.5 mm diameter and mass of 7.5 g in an air gun. Analytical expressions were obtained to find the ballistic limit, residual velocity and energy absorption capacity of the laminates. The expressions obtained by considering the various damage modes, which were involved in penetration, when laminates subjected to impact loading. The values obtained from analysis were compared with experimental results and good agreement was found. The strain rate sensitivity of the glass/epoxy composites was considered for analysis. 相似文献
4.
In this investigation, Polyetherimide (PEI) reinforced with multi-walled carbon nanotube (MWCNT) using novel melt blending technique. Surface of MWCNTs are modified by acid treatment as well as by plasma treatment. PEI nano composites with 2 wt% treated MWCNT shows about 15% improvement in mechanical properties when compared to unfilled PEI. The thermal decomposition kinetics of PEI/MWCNT nano composites has been critically analyzed by using Coats – Redfern model. The increase in activation energy for thermal degradation by 699 kJ/mol for 2 wt% MWCNT implies improvement in the thermal properties of PEI. Studies under Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM) depict significant interfacial adhesion with uniform dispersion of MWCNT in polymer matrix due to surface functionalization. 0.5 wt% chemically modified MWCNT shows typical alignment of MWCNT. There is a significant improvement in mechanical properties and thermal properties for surface functionalized MWCNT reinforced. 相似文献
5.
Polyether imides (PEI)/silica nanocomposites, prepared by sol–gel process, were used to modify the epoxy resin (ER), and the effect of silica particles on reaction-induced phase separation and mechanical properties of these systems were investigated. SEM images of the fracture surface of ER/PEI/silica composites showed an interesting morphology transformation with the increase of silica particle content. SEM–EDX results indicated that silica particles once formed in the PEI gradually migrated and concentrated in epoxy-rich region during the phase separation because of the better affinity between silica particles and epoxy resin. FTIR measurement and rheological test confirmed that the silica particles make the polymerization reaction of epoxy faster and the dynamic DSC results demonstrated that the activation energy of these systems decreased with the increase of the silica particles. Mechanical measurements approved that the introducing of PEI/silica nanocomposites into the epoxy could lead to great improvement of the impact strength and storage module. 相似文献
6.
Preparation and characterization of new quaternized carboxymethyl chitosan/rectorite nanocomposite 总被引:1,自引:0,他引:1
Xiaoying Wang Bo Liu Junli Ren Chuanfu Liu Xiaohui Wang Jun Wu Runcang Sun 《Composites Science and Technology》2010
Quaternized carboxymethyl chitosan (QCMC) was intercalated into the interlayer of rectorite (REC) to prepare QCMC/REC nanocomposite. XRD and TEM results revealed that REC was well dispersed in the polymer matrix and obtained the largest interlayer distance when the mass ratio of QCMC to REC was 2:1. FTIR, NMR and zeta-potential analyses showed that the intercalation of QCMC did not destroy the structure of REC layer, but there were hydrogen-bonding and electrostatic interactions between QCMC and REC. Quaternized chitosan (HTCC)/REC nanocomposite was prepared and studied in parallel. The comparative analysis of the two biopolymer/clay nanocomposites indicated that the free volume and positive charge density of biopolymers were important factors that affected the intercalation of biopolymer into clay. At last, thermal analysis indicated that QCMC/REC nanocomposites had obviously higher thermal stability in comparison with QCMC. This study shows that the combination with clay materials is a functional way to expand the possible application of QCMC as drug controlled-release carriers, antimicrobial agent and pulp-cap. 相似文献
7.
Kuo-Yi Li Chen-Feng Kuan Hsu-Chiang Kuan Chia-Hsun Chen Ming-Yuan Shen Jia-Ming Yang Chin-Lung Chiang 《Materials Chemistry and Physics》2014
2-(Diphenylphosphino)ethyltriethoxy silane (DPPES) was grafted onto the surface of graphene oxide nanosheets (GON) via a condensation reaction. X-ray photoelectron spectroscopy, X-ray diffractometry, Fourier transform infrared spectroscopy and Raman spectroscopy verify that DPPES did not only covalently bond to GON as a functionalization moiety, but partly restored its conjugated structure as a reducing agent. DPPES on graphene sheets oxide was observed by transmission electron microscopy, and contributed to the favorable dispersion of DPPES-GON in nonpolar toluene. Additionally, the flame retardancy and thermal stability of epoxy/DPPES-GON nanocomposites that contain various weight fractions of DPPES-GON were studied using the limiting oxygen index test, UL-94 test and by thermogravimetric analysis in nitrogen. The composites containing 10 wt% DPPES-GON can pass V-0 rating in UL-94 test. Adding 10 wt% DPPES-GON in epoxy greatly increased the char yield and LOI by 42% and 80%, respectively. Epoxy/DPPES-GON nanocomposites with phosphorus, silicon and graphene layer structures were found to exhibit much greater flame retardancy than neat epoxy. The synergistic effects among silicon, phosphorus and GON can improve the flame retardancy of epoxy resin. 相似文献
8.
Yun Yu 《Materials Research Bulletin》2011,46(10):1593-1599
Polyimide/sepiolite nanocomposite films have been prepared via an in situ polymerization method. The process involves the dispersion of sepioite in N,N-dimethylacetamide, polycondensation of 2,2′-bis [4-(3,4-dicarboxyphenoxy) phenyl] propane dianhydride and 4,4′-oxydianiline in the presence of sepiolite suspension to form poly(amic acid), and the thermal imidization of poly(amic acid)/sepiolite nanocomposite. The morphology, thermal and mechanical performance, and water absorption of nanocomposite films were systematically studied with various sepiolite contents. The results indicated that sepiolite was dispersed homogeneously at a nanometer scale in polyimide matrix. Owing to such nanodispersion of sepiolite, the polyimide/sepiolite nanocomposite films exhibit dramatic improvements on the mechanical properties and the coefficient of thermal expansion while fine thermal stability and low water absorption capacity were also maintained. When the sepiolite content increased to 16% the polyimide/sepiolite nanocomposite film achieved as much as 41% and 94% increase on the tensile strength and modulus respectively, and 50% decreased in coefficient of thermal expansion. 相似文献
9.
Qing-zhou Zhai Tian-su JiangWei-hua Hu Xin GuanWei Wang Shilun Qiu 《Materials Research Bulletin》2002,37(11):1837-1842
The host-guest nanocomposites (Y zeolite)-sulfides (FeS, CoS, NiS) were successfully prepared by a hydrothermal method and characterized by powder XRD, chemical analysis, adsorption technique, infrared spectroscopy and X-ray photoelectron spectroscopy. The Y zeolite-NiS host-guest nanocomposite material was found to exhibit luminescence. This paper suggests that the luminescence mechanism of Y-NiS resulted from the excitons in the confinement areas and from the defects in the materials. The material Y-NiS may be used as luminescent materials. 相似文献
10.
This paper focuses on the humid aging of a high temperature thermosetting resin employed for the realization of aircraft parts manufactured by the RTM process. Accelerated humid aging at several different temperatures (40–90 °C) and relative humidity values (50–100%) has been carried out by means of gravimetric tests. Anomalous behavior with respect to Fick’s diffusion law and a color gradient from the edge to the center of the samples has been observed. Drying of samples after aging and mechanical tests on aged and dried samples have shown the existence of irreversible phenomena taking place during humid ageing: uniform tensile tests revealed resin embrittlement, Ultra Micro Indentation tests allowed measuring a gradient of properties from the surface to the centre of the samples. This behavior – associated to the color changes observed on aged samples – indicates that oxidation phenomena take place during hygrothermal aging. 相似文献
11.
Bai-Huan Xu Dong-Ya Sun Cong Ding Xue-Zhong Liu Zi-Jing Xiao 《Materials Research Bulletin》2007,42(9):1633-1639
Layered nanocomposite PEG/WS2, intercalating oligomeric poly(ethylene glycol) (PEG6000) into the tungsten disulfide host galleries, was synthesized using the exfoliation-adsorption technique. X-ray diffraction revealed that the intercalated oligomer within the host galleries is in a double-layer arrangement with an interlayer expansion of about 8.8 Å. The optimum conditions were explored to prepare the single-phase product with a composition of Li0.12(PEG)1.51WS2. Thermal analyses suggested that the resulting material shows good thermal stability, with the decomposition of the interacted oligomeric chains within the disulfide galleries occurring at around 258 °C. Despite high conductivity of the host material, those of the PEG/WS2 nanocomposite were found to be high in the order of 1 × 10−2 S cm−1 at ambient temperature, resulted from the host guest-host charge transfers. 相似文献
12.
In this paper, we studied the water transport in thermoset matrices. We used Fourier Transform Infrared analysis (FTIR) during sorption/desorption experiments to investigate the interaction between sorbed water and the epoxy network. Our results demonstrated that the polymer matrix undergoes hydrolysis. We found that the chemical species involved in the reaction process was the residual anhydride groups. These results support the physical basis of the three-dimensional (3D) diffusion/reaction model. We finally showed that this model is able to reproduce multi-cycle sorption/desorption experiment, as well as water uptake in hybrid metal/epoxy samples. We simulated the 3D distributions of the diffusing water and the reacted water. 相似文献
13.
The thermal conductivity of hollow glass bead (HGB)-filled polypropylene (PP) composites was estimated using the thermal conductivity equation of inorganic hollow microsphere-filled polymer composites published in the previous paper. The estimations were compared with the measured data of the PP composites filled with two kinds of HGB with different size (the mean diameter was respectively 35 μm and 70 μm). The results showed that the predictions of the thermal conductivity were in good agreement with the measured data except to individual data points. Furthermore, both the estimated and measured thermal conductivity decreased roughly linearly with increasing the HGB volume fraction when the HGB volume fraction was less than 20%; the influence of the particle diameter on the thermal conductivity was insignificant. 相似文献
14.
The paper presents a study about the glass transition of commercially available epoxy resins used for structural strengthening of concrete members for instance by means of Carbon Fiber Reinforced Polymer (CFRP) strips. Prior to an experimental investigation with a dynamic mechanical analysis (DMA), an overview on differences between definitions for the glass transition temperature Tg is given. Several testing recommendations are listed in this respect. Subsequently, DMA tests on three commercially available products are presented. A first focus is put on the different evaluation methods for one specific test result. It is visible that considerable differences in the finally adapted glass transition temperature might arise if one or the other procedure is followed. Additional parameters, such as curing procedure, specimen age, temperature history, and ultimate temperature during heating are considered, too. In all the above mentioned cases, differences in the glass transition can be found. Higher specimen age, higher ultimate temperature during testing, accelerated curing, as well as a lower heating rate implicate higher glass transition temperatures, showing that the glass transition temperature is not a fixed material characteristic. In a final step, the relevance for Tg for civil engineering applications is described. The various design code provisions for defining the service temperature in structures related to Tg are presented. The overall aim of the investigation is to show that structural engineers and end users have to be aware of the different influential parameters on the final results regarding the glass transition temperature, which also highlights the need of a potential deeper product investigation in case technical data sheets lack detailed information. 相似文献
15.
Halloysite nanotubes (HNT) were effectively incorporated into epoxy resin and used for infusion of carbon fibre textiles, resulting in epoxy/halloysite nanotube/carbon fibre (EP/HNT/CF) multi-scale composites. The distribution of nanotubes in the composites was examined by SEM. The thermomechanical properties of the composites were characterized by dynamic mechanical analyser (DMA). A 25% enhancement was recorded for the storage modulus of EP/HNT/CF composite in the glassy state. Moreover, the Tg of the laminates increased with the addition of HNT, and the values were even higher than the Tg of their matrix. Additionally, the Izod impact strength of the composites has been improved. These results indicate a synergistic effect between HNT and carbon fibres. 相似文献
16.
This paper reports the accelerated thermal ageing behaviors of pure epoxy resin and 3-D carbon fiber/epoxy braided composites. Specimens have been aged in air at 90 °C, 110 °C, 120 °C, 130 °C and 180 °C. Microscopy observations and attenuated total reflectance Fourier transform infrared spectrometry analyses revealed that the epoxy resin oxidative degradation only occurred within the surface regions. The surface oxidized layer protects inner resin from further oxidation. Both the resin degradation and resin stiffening caused by post-curing effects will influence the compression behaviors. For the braided composite, the matrix ageing is the main ageing mode at temperatures lower than glass transition temperatures (Tg) of the pure epoxy resin, while the fiber/matrix interface debonding could be observed at the temperatures higher than Tg, such as the temperature of 180 °C. The combination of matrix degradation and fiber/resin interface cracking leads to the continuous reduction of compressive behaviors. 相似文献
17.
Notched and unnotched Izod impact strength of cellulose nanofibers (CNFs) and microfibrillated cellulose (MFC)-filled impact modified polypropylene (PP) composites were measured and compared with microcrystalline cellulose (MCC)-filled composites. An Izod impact fracture initiation resistance theory was formulated and a characteristic impact resistance model was developed to evaluate the unique impact characteristics of cellulose nanofibril-filled PP composites. As filler loading increased CNF and MFC-filled composites showed higher characteristic impact resistance than MCC-filled ones. Among the cellulose fillers used in this study, CNF were found to be the most resistant of the three materials tested in terms of characteristic impact resistance. Even though impact resistance in not the only evaluation tool, characteristic impact resistance is an evaluation tool used to determine the material’s unique and hidden impact characteristics. The characteristic impact resistance model is useful for analysis of the impact behavior of any polymer composite material. It was also found that impact modified PP used in this study is more fracture resistant, but more crack sensitive, than conventional PP. 相似文献
18.
Ke-Zhao Du Wan-Biao Hu Bing Hu Xiang-Feng Guan Xiao-Ying Huang 《Materials Research Bulletin》2011,46(11):1969-1974
A new indium selenide, namely (bdaH)InSe2 (1) (bda = 1,4-butanediamine) has been solvothermally synthesized and structurally characterized. It belongs to the non-centrosymmetric space group Fdd2. Its structure features an infinite one-dimensional anionic chain of [InSe2]nn− with monoprotonated [bdaH]+ as charge compensating cation. The organic [bdaH]+ cations are joined into a supramolecular one-dimensional chain via N–H···N hydrogen bonding, which further interacts with the inorganic chain via N–H···Se and C–H···Se hydrogen bonding, forming a supramolecular three-dimensional network. Based on such a well-defined structure, the thermal stability, optical, conductivity, and dielectric properties were systematically investigated, showing that dielectric constant, as well as conductivity, had a hump at about 95 °C, which could be attributed to water molecules in the crystal boundary. 相似文献
19.
Jayesh D. Patel 《Materials Research Bulletin》2009,44(8):1647-11504
A simple solution growth method for synthesis of nanocomposite of PbS nanoparticles in poly(vinyl-pyrrolidone) (PVP) polymer is described. The nanocomposite is prepared from methanolic solution of lead acetate (PbAc), thiourea (TU) and PVP at room temperature (∼27 °C). Optical absorption spectrum of PbS/PVP nanocomposite solution shows strong absorption from 300 to 650 nm with significant bands at 400 and 590 nm which is characteristic of nanoscale PbS. Spin-coated nanocomposite films on glass have an absorption edge at ∼650 nm with band gap of 2.55 eV. Fourier transform infrared (FTIR) spectroscopy of PbS/PVP nanocomposite and PVP shows strong chemical bond between PbS nanoparticles and host PVP polymer. The transmission electron microscope (TEM) images reveal that 5-10 nm PbS particles are evenly embedded in PVP polymer. The formation of PbS is confirmed by selective area electron diffraction (SAED) of a typical nanoparticle. 相似文献
20.
Synergistic flame retardancy effect of graphene nanosheets and traditional retardants on epoxy resin
Novel non-toxic halogen-free flame retardants are replacing traditional flame retardants in polymer and polymer matrix composite structures. In this study, graphene nanosheet (GNS) is investigated in combination with traditional layered double hydroxide (LDH), layered rare-earth hydroxide (LRH), and phosphorus-based flame retardant (DOPO) to enhance the flame retardancy of epoxy resin. A synergistic flame retardancy effect is achieved in GNS/LDH and GNS/DOPO systems where combined GNS and LDH increased the viscosity of the epoxy melt, and limited the flame propagation through inhibition of dripping. The limiting oxygen index of epoxy increased from 15.9 to 23.6 with addition of 0.5 wt.% each of GNS and LDH. With the addition of 2.5 wt.% of both GNS and LDH, the total heat release of epoxy resin also reduced from 33.4 MJ/m2 to 24.6 MJ/m2. The synergistic effect of GNS and DOPO adopted a different mechanism. The addition of 2.5 wt.% of GNS and DOPO reduced the peak heat release rate from 1194 kW/m2 to 396 kW/m2, and the total heat release rate from 72.5 MJ/m2 to 48.1 MJ/m2. The synergistic mechanisms of the flame retardants were closely analyzed and correlated with the flame retardant properties. 相似文献