Showing papers on "Epoxy published in 2001"
TL;DR: In this article, the effect of fiber treatment on the mechanical properties of unidirectional sisal-reinforced epoxy composites was investigated, and the relationship between optimized fiber treatment and performance improvement of sisal composites is proposed.
860 citations
TL;DR: A new class of epoxy nanocomposites with completely defined organic/inorganic phases was prepared by reacting octakis(glycidyldimethylsiloxy)octasilsesquioxane with diaminodiphenylmethane (DDM) at various compositional ratios and the effects of reaction curing conditions on nanostructural organization and mechanical properties were explored.
Abstract: A new class of epoxy nanocomposites with completely defined organic/inorganic phases was prepared by reacting octakis(glycidyldimethylsiloxy)octasilsesquioxane [(glydicylMe2SiOSiO1.5)8] (OG) with diaminodiphenylmethane (DDM) at various compositional ratios. The effects of reaction curing conditions on nanostructural organization and mechanical properties were explored. A commercial epoxy resin based on the diglycidyl ether of bisphenol A (DGEBA) was used as a reference material throughout these studies. FTIR was used to follow the curing process and to demonstrate that the silsesquioxane structure is preserved during processing. OG/DDM composites possess comparable tensile moduli (E) and fracture toughness (KIC) to, and better thermal stabilities than, DGEBA/DDM cured under similar conditions. Dynamic mechanical analysis and model reaction studies suggest that the maximum cross-link density is obtained at N = 0.5 (NH2:epoxy groups = 0.5) whereas the mechanical properties are maximized at N = 1.0. Digestio...
479 citations
TL;DR: In this article, the interfacial effect on properties of epoxy composites was investigated by using infrared and raman spectroscopy, differential scanning calorimetry (DSC), and particle size analyzer.
443 citations
TL;DR: In this article, three different curing agents were used: an aliphatic diamine, two cycloalaphatic diamines and a cyclo-aliphatic cyclophilic diamine.
403 citations
TL;DR: In this paper, a two-part epoxy resin is used as the repair medium, the two components being diluted with solvent and infiltrated into different plies of a composite based on ‘Hollex S2-glass fibre.
Abstract: The widespread use of polymer composites is still caveated with concerns about the loss in structural performance that can result from impact damage. Such events give rise to delaminations which may not be easily detectable by eye. This paper describes a technique for ‘smart’ repair of delaminations in polymer composites. This involves the filling of hollow fibres with a resin, which is released into the damaged area when the fibre is fractured. A two-part epoxy resin is used as the repair medium, the two components being diluted with solvent and infiltrated into different plies of a composite based on ‘Hollex’ S2-glass fibre. Compression strength after impact tests were used as a measure of the effectiveness of the repair technique, and a potential improvement was noted after application of heat and vacuum to the damaged composite. Resin release from the fibres was noted by microscopy. A more comprehensive study is required to verify the improvement in post-impact strength, and the use of larger internal diameter fibres would enhance the amount of resin released.
384 citations
TL;DR: In this article, X-ray scattering and atomic force microscopy were used to investigate the exfoliation of octadecyl amine treated montmorillonite clays in epoxy.
322 citations
TL;DR: In this article, the parabolic Mohr failure criterion was applied to experimental results under different loading conditions and the results of the mechanical tests and a fractographic study of the fracture surfaces were correlated with the stress-state-dependent strength and fracture stress of the epoxy resin.
314 citations
TL;DR: In this article, the characteristics of water sorption and diffusion in an amine-cured epoxy system based on tetraglycidyl diaminodiphenylmethane and a novolac glycidyl ether resin were studied as a function both of the polymer microstructure, known from previous works, and the temperature.
Abstract: The characteristics of sorption and diffusion of water in an amine-cured epoxy system based on tetraglycidyl diaminodiphenylmethane and a novolac glycidyl ether resin were studied as a function both of the polymer microstructure, known from previous works, and the temperature. Water-sorption experiments and dynamic mechanical analysis (DMA) were performed. Tensile stress–strain and Rockwell hardness tests were conducted to investigate the effects of absorbed water on the mechanical properties of the material. Competing effects of the sorption of water in the free volume and of strong interactions between water molecules and polar groups of the network were used to explain the diffusional behavior observed, which followed Fick's second law. DMA analysis seemed to be sensitive to the water effects and the viscoelastic behavior was related both to the water-sorption processes and to the microstructure of the system. An important impact of water uptake on the tensile properties at break was also appreciated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 71–80, 2001
298 citations
TL;DR: In this article, a novel phosphorus-containing novolac (DOPO-PN) from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10oxide and 4-hydroxyl benzoaldehyde was obtained via simple addition reactions.
298 citations
TL;DR: In this paper, the chemical modification of oil palm empty fruit bunch (EFB) and coconut fibre (coir) using non-catalysed acetic anhydride were investigated, and an increase in the interfacial shear strength between acetylated fibres and hydrophobic resins was noted.
270 citations
TL;DR: Aliphatic epoxy composites with multifunctional polyhedral oligomeric silsesquioxane (POSS) nanophases (epoxy/POSS 95/5 and 75/25) and epoxy blends with the prepolymer of ladder-like polyphenylsilsesquioxanes (PPSQ) (95/5, 90/10, and 85/15) were prepared by solution casting and then curing.
Abstract: Aliphatic epoxy composites with multifunctional polyhedral oligomeric silsesquioxane (POSS) ((C6H5CHCHO)4(Si8O12)(CHCHC6H5)4) nanophases (epoxy/POSS 95/5 and 75/25) and epoxy blends with the prepolymer of ladderlike polyphenylsilsesquioxane (PPSQ) (95/5, 90/10, and 85/15) were prepared by solution casting and then curing. These composites and blends were studied by dynamic mechanical thermal analysis (DMTA) and mechanical testing. The POSS units incorporated into the epoxy network are well dispersed in the composite, probably on the molecular scale, even at high POSS content (25 wt %) based on TEM observations. However, the aliphatic epoxy/PPSQ blends exhibit good miscibility only at low PPSQ content (≤10 wt %). Phase separation was clearly observed when the PPSQ content was 15%. Incorporation of the POSS macromer into this epoxy network by curing at upper temperatures of 120 and 150 °C broadened the temperature range of glass transition of the resulting composites but has almost no influence on their Tg ...
TL;DR: In this paper, the effect of voids on carbon/epoxy and carbon/bismaleimide fabric laminates is compared in terms of the corresponding fracture parameters and the shape and the location of the voids.
TL;DR: In this paper, both fully soluble and phase-separating epoxy-functionalised hyperbranched polymers were used, the latter showing more efficient toughening properties, but a close control of the phase separation mechanism was required, in order to avoid filtering effects before or during fibre impregnation.
TL;DR: In this article, two novel flame-retardant curing agents for epoxy resins, [ODOPM-PN] and [ ODOPM−MPN], were prepared from phenol formaldehyde novolac (PN), melamine-phenol (MPN) and a reactive 2-(6-oxid-6H-dibenz) 6-methanol methanol (ODOPm) while ODOPm was synthesized through the reaction between 9,10-dihydro-9-oxa-10-ph
TL;DR: A series of water-based stable sol-gel systems have been developed as mentioned in this paper, where various functional groups including amino, epoxy, vinyl, and allyl groups can be incorporated into the solgel network to interact with organic polymer resins.
TL;DR: In this article, the use of high quality natural fibres as reinforcements was studied using the resin transfer molding (RTM) processing technique and the results from mechanical testing showed that the (50/50) high quality ArcticFlax/epoxy composite has a stiffness of about 40 GPa compared to the stiffness in pure epoxy of 3.2 GPa.
Abstract: In this work the use of high quality natural fibres as reinforcements was studied using the resin transfer moulding (RTM) processing technique. The fibres were unidirectional high quality ArcticFlax and the matrix was an epoxy resin. The mechanical properties of the composites were compared to conventional RTM manufactured glass fi- bre composites, traditionally retted UD-flax fibre composites and to the pure epoxy. The results from mechanical testing showed that the (50/50) high quality ArcticFlax/epoxy composite has a stiffness of about 40 GPa compared to the stiffness in pure epoxy of 3.2 GPa. The same composite has a tensile strength of 280 MPa compared to 80 MPa of the ep- oxy. RTM showed to be a suitable processing technique for natural fibre composites when high quality laminates are preferred.
Patent•
30 Aug 2001TL;DR: In this article, the authors presented improved compositions and methods of using the compositions for sealing underground zones, which are comprised of water, an aqueous rubber latex, an organophilic clay, sodium carbonate, an epoxy resin and a hardening agent for said epoxy resins.
Abstract: The present invention provides improved compositions and methods of using the compositions for sealing subterranean zones. One composition of the invention is comprised of water, an aqueous rubber latex, an organophilic clay, sodium carbonate, an epoxy resin and a hardening agent for said epoxy resin.
TL;DR: The impact behavior and post impact compressive characteristics of glass-carbon/epoxy hybrid composites with alternate stacking sequences have been investigated in this paper, where plain weave E-glass and twill weave T-300 carbon have been used as reinforcing materials.
Abstract: Impact behaviour and post impact compressive characteristics of glass–carbon/epoxy hybrid composites with alternate stacking sequences have been investigated. Plain weave E-glass and twill weave T-300 carbon have been used as reinforcing materials. For comparison, laminates containing only-carbon and only-glass reinforcements have also been studied. Experimental studies have been carried out on instrumented drop weight impact test apparatus. Post impact compressive strength has been obtained using NASA 1142 test fixture. It is observed that hybrid composites are less notch sensitive compared to only-carbon or only-glass composites. Further, carbon-outside/glass-inside clustered hybrid configuration gives lower notch sensitivity compared to the other hybrid configurations.
TL;DR: In this paper, the use of low molecular weight reactive solvents as processing aid and dispersing agent was investigated for the dispersion of fumed silica particles in polyethersulphone (PES) matrix.
TL;DR: In this paper, spherical micelles and vesicles were characterized by transmission electron microscopy and small-angle X-ray scattering (SAXS) data, respectively.
Abstract: Amphiphilic block copolymers provide a unique means for toughening epoxy resins because they can self-assemble into different inclusion shapes before epoxy curing. The two examples reported here are spherical micelles and vesicles, which form in blends containing epoxy and symmetric or asymmetric poly(ethylene oxide)–poly(ethylene-alt-propylene) (PEO–PEP) block copolymer with PEO volume fractions of 0.5 and 0.26, respectively. The vesicles and spherical micelles were characterized by transmission electron microscopy and small-angle X-ray scattering (SAXS), respectively. SAXS data from the spherical micelles were fit to the Percus–Yevick model for a liquid-like packing of spheres with hard-core interactions. Mechanical properties of spherical-micelle-modified and vesicle-modified epoxies in the dilute limit are compared. The glass-transition temperature and Young's (storage) modulus were tested with dynamic mechanical spectroscopy, and compact-tension experiments were performed to determine the critical plane-strain energy release rate for fracture. Vesicles were most effective in improving the epoxy fracture resistance. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2996–3010, 2001
TL;DR: In this article, the authors used parallel plate rheometry to measure the material behavior below the gel point of the epoxy network and converted the data to the stress relaxation modulus for comparison of the material behaviour among various cure states and between the two experimental techniques.
Abstract: The cure dependent relaxation modulus of an epoxy resin was investigated over the entire range of cure extent. Parallel plate rheometry was used to measure the material behavior below the gel point of the epoxy network. Creep testing in three-point bend was used for specimens cured past gelation. All data were converted to the stress relaxation modulus for comparison of the material behavior among the various cure states and between the two experimental techniques. The data were used to develop a practical model for predicting the cure dependence of the relaxation modulus throughout cure under varying processing conditions.
TL;DR: In this article, a series of novel multifunctional phosphorus-containing epoxy resins (phosphorus content 2 and 4%) were synthesized from the addition reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) and the glycidyl ether of cresol formaldehyde novolac (functionalitya 12, C12) and then cured with 4,4 0 -diaminodiphenyl sulfone (DDS), phenol novol
TL;DR: In this article, various hygroscopic effects of such parameters as hygrothermal temperature, matrix volume ratio, void volume ratio (Vv), specimen thickness, lay-up sequence and internal stress were investigated for epoxy/carbon fiber composite laminates.
Abstract: In this study, various hygroscopic effects of such parameters as hygrothermal temperature, matrix volume ratio (Vm), void volume ratio (Vv), specimen thickness, lay-up sequence and internal stress were investigated for epoxy/carbon fiber composite laminates. The specimen thickness and lay-up sequence had little effect on the through-the-thickness water absorption behavior of composite laminates, but the other parameters affected the moisture absorption rate and equilibrium water uptake in different ways and intensities. The glass transition temperature of composite laminates was strongly affected and linearly decreased by the quantity of equilibrium water uptake. A characteristic length of moisture migration through the unidirectional laminates was proposed as a function of fiber angle to the exposed laminate surface. In this approach, the fibers imbedded in the matrix were assumed to act as a barrier to the penetrating water molecules, and the developed model was well compared with the experimental results.
TL;DR: In this paper, the authors present a study on delamination growth in Mode I, Mode II and mixed mode under fatigue loading in an HTA/6376C composite and determine the threshold values of the strain energy release rate for delamination growth.
Abstract: This paper presents a study on delamination growth in Mode I, Mode II and mixed mode under fatigue loading in an HTA/6376C composite. The computed slopes of the modified Paris plots were high. Therefore, threshold values of the strain energy release rate for delamination growth were determined. Low fatigue threshold values revealed a significant effect of fatigue loading. The largest effect was found for the ENF test (Mode II) for which the fatigue threshold value was only 10% of the critical strain energy release rate in static tests. Threshold values for MMB (mixed mode) and DCB (Mode I) tests were 15% and 23% of the static values, respectively. Fractographic evaluation revealed identical initial failure mechanisms in fatigue and static loading conditions for the ENF specimen. The ENF specimen failed by formation and coalescence of microcracks. The low fatigue threshold for the ENF specimen was explained by microscopical observations on the specimen edge. It was also shown that the fracture surfaces generated in static and fatigue DCB and MMB tests were similar.
TL;DR: In this article, a nanometer-scale silica formed in the epoxy resin was characterized with Fourier transform infrared, NMR, and scanning electron microscopy, showing an enhancement effect of improving the flame-retardant properties of the resins.
Abstract: Phosphorus-containing epoxy-based epoxy–silica hybrid materials with a nanostructure were obtained from bis(3-glycidyloxy)phenylphosphine oxide, diaminodiphenylmethane, and tetraethoxysilane in the presence of the catalyst p-toluenesulfonic acid via an in situ sol–gel process The silica formed on a nanometer scale in the epoxy resin was characterized with Fourier transform infrared, NMR, and scanning electron microscopy The glass-transition temperatures of the hybrid epoxy resins increased with the silica content The nanometer-scale silica showed an enhancement effect of improving the flame-retardant properties of the epoxy resins The phosphorus–silica synergistic effect on the limited oxygen index (LOI) enhancement was also observed with a high LOI value of 445 © 2001 John Wiley & Sons, Inc J Polym Sci A: Polym Chem 39: 986–996, 2001
TL;DR: In this article, a study on the galvanic corrosion between carbon-fiber-reinforced plastics (CFRP) laminates and steel is presented. And the effect of the sizing agent on the corrosion rate is investigated, and three different solvents are used to remove the sizing agents from the surface of the carbon fibers.
Abstract: The demand for the use of carbon-fiber-reinforced plastics (CFRP) in rehabilitation of deteriorating infrastructure is increasing worldwide. The design characteristics of reinforced concrete or steel members can be enhanced significantly by epoxy bonding CFRP laminates to the critically stressed tension areas. There is, however, a concern regarding possible galvanic corrosion when carbon and steel are bonded together. This paper presents the result of a study on the galvanic corrosion between CFRP laminates and steel. A total of 38 specimens made of steel and carbon fibers were prepared and tested. Two simulated aggressive environments and three different amounts of epoxy coating were used in addition to samples with no coating at all. Furthermore, the effect of the sizing agent on the galvanic corrosion rate was investigated, and three different solvents were used to remove the sizing agents from the surface of the carbon fibers. Potentiodynamic polarization and galvanic corrosion tests were conducted. T...
TL;DR: In this article, the authors investigated the dielectric properties of BaTiO 3 /epoxy composites with different types of treated ceramic powders and measured the properties of these composites as functions of temperature and frequency.
Abstract: Multi-doped BaTiO 3 /epoxy composites with the different types of treated ceramic powders are under investigation. The ceramic/epoxy composite with the 900°C treated ceramic powder has the highest dielectric constant, while lower values for those with powders treated at higher temperatures. Longer grinding of 20 h can have different heat-treated composites with similar dielectric constants. Dielectric properties of these composites were measured as functions of temperature and frequency. The increase of dielectric loss at frequencies above 1 MHz is due to the mechanism of domain-wall motion. The composite with semi-conducting fillers can have a limited increase in dielectric constant, but a large increase in dielectric loss. To have the best dielectric properties of the multi-doped BaTiO 3 /epoxy composite thick films for the printed wiring boards, the ceramic ratio need to be maximized without losing the board flexibility. A proper powder treatment is required to maximize the powder loading and performance.
TL;DR: In this article, the response of carbon/epoxy laminated composites under high strain rate compression loading is considered using a modified split Hopkinson Pressure Bar (SHPB) setup at three different strain rates of 82, 164 and 817 s −1.
TL;DR: In this paper, the storage modulus in the rubbery region increased and the peak area of the tan δ curves in the glass transition region decreased, respectively, with the hybrization of small amounts of silica.
TL;DR: In this article, a strain-induced frequency shift of tangential Raman active modes of single-wall carbon nanotubes (SWNTs) embedded in epoxy resin subjected to bending is presented.
Abstract: Raman spectroscopy is used to infer elastic properties of single-wall carbon nanotubes (SWNTs) in composites. This letter presents strain-induced frequency shift of tangential Raman active modes of SWNTs embedded in epoxy resin subjected to bending. Epoxy curing and sample extension in the tensile strength test are found to create residual strains on the SWNT ropes. We demonstrate that specimen compression in combination with the Raman microprobe technique provides a means for determining of these strains and hence load transfer effectiveness.