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Epoxy Matrix (epoxy + matrix)
Selected AbstractsDielectric monitoring of curing of liquid oligomer-modified epoxy matricesPOLYMER INTERNATIONAL, Issue 9 2001G Kortaberria Abstract Dielectric measurements were performed in ,real-time' at several temperatures to follow polymerization reactions on blends of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin with 4, 4,-diaminodiphenylmethane (DDM) hardener and different amounts of polyoxypropylenetriamine (POPTA) oligomer. These systems exhibit phase separation induced by molar mass increasing through curing of the resin. Monitoring of phase separation and vitrification (related to the ,-relaxation) was performed by this technique. The results are compared with those for the unmodified resin,hardener mixture. The change of the main ,-relaxation with cure time, cure temperature, and amount of modifier was measured for the mixtures. This change of the main relaxation through curing in the frequency domain was indicative of the cure reaction advancement, because of its dependence on the viscosity of the medium. The change of the ionic conductivity during curing was also analysed, showing its dependence upon cure temperature. © 2001 Society of Chemical Industry [source] Asymmmetric Diamino Functionalization of Nanotubes Assisted by BOC Protection and Their Epoxy NanocompositesADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Yao Zhao Abstract Homogenous dispersion and strong interfacial bonding are prerequisites for taking full advantage of the mechanical properties of nanotubes in a composite. In order to simultaneously achieve both conditions, a highly efficient and mechanically non-destructive functionalization of nanotubes is developed. With fluoronanotubes as the precursor, asymmetric diamine molecules, N -BOC-1,6-diaminohexane, are used to replace fluorines on the wall of fluoronanotubes and construct covalent bonding to the surface of the nanotubes. A BOC de-protection reaction is conducted and the resulting exposed amino groups create strong covalent bonds with the matrix in the course of epoxy ring-opening etherification and curing chemical reactions. In comparison with the conventional functionalization based on symmetric diamine molecules, the functionalized nanotubes derived from the BOC-protected diamine molecule are more dispersed within the epoxy matrix. Dynamic mechanical analysis shows that the functionalized nanotubes have better crosslinking with the matrix. The composites reinforced by the nanotubes demonstrate improvement in various mechanical properties. The Young's Modulus, ultimate tensile strength, and storage modulus of composites loaded with 0.5 wt% functionalized nanotubes are enhanced by 30%, 25%, and 10%, respectively, compared with the neat epoxy. The increase of the glass transition temperature, as much as 10 °C, makes the composites suited for engineering applications under higher temperatures. The new functionalization method allows for an competitive enhancement in the composite performance in use of relatively low cost raw nanotubes at a small loading level. The reinforcement mechanism of the functionalized nanotubes in the epoxy resin is discussed. [source] Sensors: Glass Fibers with Carbon Nanotube Networks as Multifunctional Sensors (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Mater. A semiconductive interphase between a glass fi ber and an epoxy matrix is achieved by coating carbon nanotubes on the glass fiber, as reported by S.-L. Gao, E. Mäder, et al. on page 1885. The interphase at the nanoscale provides multifunctional sensibility, which can be observed by electric force microscopy. The resulting composites with an ultra-high anisotropic electrical property are capable of detecting piezoresistive effects as well as the local glass transition temperature. [source] Self-Healing Materials: A Facile Strategy for Preparing Self-Healing Polymer Composites by Incorporation of Cationic Catalyst-Loaded Vegetable Fibers (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Mater. Discontinuous sisal fibers carrying extremely active (C2H5)2O·BF3 are embedded in epoxy matrix together with epoxy monomer-loaded microcapsules to fabricate self-healing composite based on the healing mechanism of cationic chain polymerization. This approach, described by D. S. Xiao et al. on page 2289, skips the encapsulation of high activity chemicals, reducing the risk of their deactivation during handling. It provides a facile strategy for making extrinsic self-healing polymeric materials. [source] A Facile Strategy for Preparing Self-Healing Polymer Composites by Incorporation of Cationic Catalyst-Loaded Vegetable FibersADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Ding Shu Xiao Abstract A two-component healing agent, consisting of epoxy-loaded microcapsules and an extremely active catalyst (boron trifluoride diethyl etherate, (C2H5)2O,·,BF3)), is incorporated into epoxy composites to provide the latter with rapid self-healing capability. To avoid deactivation of the catalyst during composite manufacturing, (C2H5)2O,·,BF3 is firstly absorbed by fibrous carriers (i.e., short sisal fibers), and then the fibers are coated with polystyrene and embedded in the epoxy matrix together with the encapsulated epoxy monomer. Because of gradual diffusion of the absorbed (C2H5)2O,·,BF3 from the sisal into the surrounding matrix, the catalyst is eventually distributed throughout the composites and acts as a latent hardener. Upon cracking of the composites, the epoxy monomer is released from the broken capsules, spreading over the cracked planes. As a result, polymerization, triggered by the dispersed (C2H5)2O,·,BF3, takes place and the damaged sites are rebonded. Since the epoxy,BF3 cure belongs to a cationic chain polymerization, the exact stoichiometric ratio of the reaction components required by other healing chemistries is no longer necessary. Only a small amount of (C2H5)2O,·,BF3 is sufficient to initiate very fast healing (e.g., a 76% recovery of impact strength is observed within 30,min at 20,°C). [source] High-Dielectric-Constant Silver,Epoxy Composites as Embedded Dielectrics,ADVANCED MATERIALS, Issue 14 2005L. Qi The incorporation of organic-coated silver nanoparticles into an epoxy matrix (see Figure, a,f represent increasing Ag content) results in a flexible 0-3 type nanocomposite with a strikingly high dielectric constant (greater than 300). The composite retains the flexibility and other mechanical properties of the polymer matrix, and may be useful in applications where capacitors are embedded into printed circuit boards. [source] Thermal degradation kinetics of epoxy/organically modified montmorillonite nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Ivan Brnardi Abstract Nanocomposites based on a commercial epoxy resin and organically modified montmorillonites (OMMTs), containing 5 and 10 phr OMMT, were prepared and characterized. Poly(oxypropylene) diamine (Jeffamine D400) and octadecylamine were used as organic modifiers. Another poly(oxypropylene) diamine (Jeffamine D230) was used as a curing agent. The thermal degradation kinetics of the neat resin system and nanocomposites were investigated by thermogravimetric analysis. The dispersion of silicate layers within the crosslinked epoxy matrix was verified by transmission electron microscopy. The activation energy of degradation for the investigated systems was determined by the isoconversional Kissinger,Akahira,Sunose method. The thermal behavior of the neat resin systems and nanocomposites was modeled with an empirical kinetic model. The influence of organic modifiers and the OMMT loading on the thermal stability of the nanocomposites was discussed. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci, 2008 [source] Morphology and mechanical and viscoelastic properties of rubbery epoxy/organoclay montmorillonite nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Amar Boukerrou Abstract The morphology and mechanical and viscoelastic properties of rubbery epoxy/organoclay montmorillonite (MMT) nanocomposites were investigated with wide-angle X-ray scattering (WAXS), transmission electron microscopy (TEM), tensile testing, and dynamic mechanical thermal analysis. An ultrasonicator was used to apply external shearing forces to disperse the silicate clay layers in the epoxy matrix. The first step of the nanocomposite preparation consisted of swelling MMT in a curing agent, that is, an aliphatic diamine based on a polyoxypropylene backbone with a low viscosity for better diffusion into the intragalleries. Then, the epoxy prepolymer was added to the mixture. Better dispersion and intercalation of the nanoclay in the matrix were expected. The organic modification of MMT with octadecylammonium ions led to an increase in the initial d -spacing (the [d001] peak) from 14.4 to 28.5 Å, as determined by WAXS; this indicated the occurrence of an intercalation. The addition of 5 phr MMTC18 (MMT after the modification) to the epoxy matrix resulted in a finer dispersion, as evidenced by the disappearance of the diffraction peak in the WAXS pattern and TEM images. The mechanical and viscoelastic properties were improved for both MMT and MMTC18 nanocomposites, but they were more pronounced for the modified ones. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 103: 3547,3552, 2007 [source] Nonaqueous synthesis of nanosilica in epoxy resin matrix and thermal properties of their cured nanocompositesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2006Tzong-Ming Lee Abstract Nonaqueous synthesis of nanosilica in diglycidyl ether of bisphenol-A epoxy (DGEBA) resin has been successfully achieved in this study by reacting tetraethoxysilane (TEOS) directly with DGEBA epoxy matrix, at 80 °C for 4 h under the catalysis of boron trifluoride monoethylamine (BF3MEA). BF3MEA was proved to be an effective catalyst for the formation of nanosilica in DGEBA epoxy under thermal heating process. FTIR and 29Si NMR spectra have been used to characterize the structures of nanosilica obtained from this direct thermal synthetic process. The morphology of the nanosilica synthesized in epoxy matrix has also been analyzed by TEM and SEM studies. The effects of both the concentration of BF3MEA catalyst and amount of TEOS on the diameters of nanosilica in the DGEBA epoxy resin have been discussed in this study. From the DSC analysis, it was found that the nanosilica containing epoxy exhibited the same curing profile as pure epoxy resin, during the curing reaction with 4,4,-diaminodiphenysulfone (DDS). The thermal-cured epoxy,nanosilica composites from 40% of TEOS exhibited high glass transition temperature of 221 °C, which was almost 50 °C higher than that of pure DGEBA,DDS,BF3MEA-cured resin network. Almost 60 °C increase in thermal degradation temperature has been observed during the TGA of the DDS-cured epoxy,nanosilica composites containing 40% of TEOS. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 757,768, 2006 [source] Use of Single-Walled Carbon Nanotubes as Reinforcing Fillers in UV-Curable Epoxy SystemsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2008Marco Sangermano Abstract CNT were dispersed in an epoxy matrix and cured by means of UV light. An increase on elastic modulus and Tg values was measured by DMTA analysis and attributed to the constraint effect of CNT on polymer chain mobility. Excellent scratch resistant coatings characterized by high critical load, small cracks and high recovery were obtained in the presence of a very low CNT content (0.025 wt.-%). TEM analysis showed some isolated CNT and some cluster agglomerations of size of about 250 nm. It was shown that it was possible to decrease the surface resistivity of the cured samples by three orders of magnitude in the presence of 0.1 wt.-% of SWCNT content. [source] Preparation and Properties of Natural Sand Particles Reinforced Epoxy CompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2007Gang Sui Abstract An epoxy composite using Cancun natural hydrophobic sand particle as filler material was fabricated in this study. Three point bending tests demonstrated an enhancement of 7.5 and 8.7% in flexural strength and flexural modulus, respectively, of epoxy composite containing 1 wt.-% sand particles without any chemical treatment involved, compared to the pristine epoxy. Scanning electron microscopy (SEM) studies revealed that the fracture toughness of the epoxy matrix was enhanced owing to the presence of sand particles in an epoxy/sand composite. Through dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) methods, it was found that the storage modulus (E,), glass transition temperature (Tg) and dimensional stability of the sand particles/epoxy composites were increased compared to the pristine epoxy. The friction behavior of epoxy/sand system reflected that the microstructure of epoxy composites was steady. These experimental results suggest that Cancun sand, as a freshly found natural micron porous material, may find promising applications in composite materials. [source] Nanoclay-reinforced syntactic foams: Flexure and thermal behaviorPOLYMER COMPOSITES, Issue 8 2010Mrinal C. Saha Syntactic foams containing 60 vol% of hollow glass microballoons in epoxy matrix are modified with untreated nanoclays using combined mechanical and ultrasonication methods. Effects of nanoclays on flexure and thermal behavior of syntactic foams are investigated by adding different amount of nanoclays in the range of 1,3% by weight. Microscopic examinations and physical property characterization are performed to determine the interactions among constituent materials and the void formation during fabrication. It is found that the syntactic foams with 2 wt% nanoclays show the highest improvement in flexural properties (,42% strength and ,18% modulus) and dynamic mechanical properties (,30% storage modulus and ,28% loss modulus) properties. Thermal decomposition temperature is found to be unaffected by the addition of nanoclays, whereas a continuous reduction in the coefficient of thermal expansion (CTE) is observed. An examination of failure surface indicates that the failure is initiated on the tension side of the flexure sample due to fracturing of microballoons. POLYM. COMPOS., 31:1332,1342, 2010. © 2009 Society of Plastics Engineers [source] Composites formed by glass fibers and PS-modified epoxy matrix.POLYMER COMPOSITES, Issue 6 2010Influence of the glass fibers surface on the morphologies, mechanical properties of the interphases generated In this work, the influence of the nature of the reinforcement surface on the interfacial morphologies developed in E-glass fibers/polystyrene (PS)-modified epoxy composites has been studied. Different surface modifications of the fibers were considered. In a complementary way, morphological analysis and nanoindentation measurements were carried out using atomic force microscopy to subsequently correlate the interfacial structure with the morphologies observed. In every composite, reaction-induced phase separation happened with a morphology composed of PS-rich domains immersed in an epoxy-rich phase. However, depending on the surface modification of the glass fibers, different distributions of PS-rich domains at the interfaces were obtained. The results were interpreted in terms of a gradual phase separation process because of stoichiometric gradients from the glass fibers surface to the matrix bulk caused by specific segregation of one of the components of the reactive epoxy mixture to the fibers occurs. It was concluded that specific and controlled reinforcement modification allows obtaining tailored interfaces formed by a polymer blend and a reinforcement in which the morphology can be previously selected. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] Modification of carbon nanotubes and its effect on properties of carbon nanotube/epoxy nanocompositesPOLYMER COMPOSITES, Issue 10 2009Zdenko, pitalský We have studied an effect of three types of modifications of carbon nanotubes (CNTs) on dispersion and mechanical properties of final epoxy-amine based nanocomposites. First approach includes end-walled covalent chemical modification at the ends of nanotubes. The second one is side-walled covalent chemical modification along the whole length of nanotubes. The third procedure is noncovalent, physical modification done by the CNT surface coating with polyaniline. The modification of nanotubes was determined by X-ray photoelectron spectroscopy. The prepared epoxy-amine nanocomposites were characterized by dynamic-mechanical analysis, tensile testing, light microscopy, transmission electron microscopy, and thermogravimetry. We observed an improvement of the mechanical properties and the thermal stability by addition of the carbon nanotubes to the epoxy matrix. The strong interactions between the nanotube and the polymer matrix were discovered in the nanocomposites with physically modified nanotubes. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Use of different alkylammonium salts in clay surface modification for epoxy-based nanocompositesPOLYMER COMPOSITES, Issue 3 2009G. Ipek Nakas Layered silicates become widely used reinforcement material in the polymer nanocomposite production in recent years due to their high aspect ratio, ease of processing, and low cost. In this present study, the aim was to evaluate the usability of a raw clay source (Resadiye, Turkey) in the production of epoxy/clay nanocomposites and to investigate the effects of different surface modifiers. For this purpose, raw Na,montmorillonite clay was first purified and then surface modified by using different types of alkylammonium salts: tetramethyl ammonium bromide, benzyl triethyl ammonium bromide, dodecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, and octadecyl trimethyl ammonium bromide. Purification and surface modification of this clay were evaluated by using the following analyses; X-ray diffraction (XRD), cation exchange capacity (CEC), particle size distribution, and dissolved organic content. These analyses simply indicated that surface modification increased both interlayer spacing between the silicate layers and CEC of the clay. These improvements were directly proportional with the chain length of the surface modifier. Nanocomposite specimens were produced by adding 0.5 wt% surface modified clay into the epoxy matrix. These specimens were characterized by XRD, Si-mapping facility of SEM, and mechanical tests. XRD results indicated an exfoliated structure whereas Si-mapping showed the uniform distribution of clay particles in epoxy, leading to improved mechanical properties, for instance more than 100% increase in fracture toughness of the neat epoxy specimen. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Comparison of mechanical properties of epoxy composites reinforced with stitched glass and carbon fabrics: Characterization of mechanical anisotropy in composites and investigation on the interaction between fiber and epoxy matrixPOLYMER COMPOSITES, Issue 8 2008Volkan Çeçen The primary purpose of the study is to evaluate and compare the mechanical properties of epoxy-based composites having different fiber reinforcements. Glass and carbon fiber composite laminates were manufactured by vacuum infusion of epoxy resin into two commonly used noncrimp stitched fabric (NCF) types: unidirectional and biaxial fabrics. The effects of geometric variables on composite structural integrity and strength were illustrated. Hence, tensile and three-point bending flexural tests were conducted up to failure on specimens strengthened with different layouts of fibrous plies in NCF. In this article, an important practical problem in fibrous composites, interlaminar shear strength as measured in short beam shear test, is discussed. The fabric composites were tested in three directions: at 0°, 45°, and 90°. In addition to the extensive efforts in elucidating the variation in the mechanical properties of noncrimp glass and carbon fabric reinforced laminates, the work presented here focuses, also, on the type of interactions that are established between fiber and epoxy matrix. The experiments, in conjunction with scanning electron photomicrographs of fractured surfaces of composites, were interpreted in an attempt to explain the failure mechanisms in the composite laminates broken in tension. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Influence of polyethersulfone modification of a tetrafunctional epoxy matrix on the fracture behavior of composite laminates based on woven carbon fibersPOLYMER COMPOSITES, Issue 5 2004B. Fernández In this study, the influence of poly(ethersulfone) (PES) as a modifying agent of a tetrafunctional epoxy matrix (TGDDM) on the mechanical behavior of composite laminates based on woven carbon fibers has been investigated. Dynamic mechanical experiments were performed on neat matrix resins and on their corresponding laminate composites. Mode-I and Mode-II fracture toughness tests for the bulk matrices and their composites, respectively, and also flexural and short beam shear tests (SBS) were carried out. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the morphologies obtained. A nanoscopic phase separation was obtained after PES addition, which was not able to stabilize the fracture process, leading, as a consequence, to a poor extent of improvement on fracture toughness properties. Polym. Compos. 25:480,488, 2004. © 2004 Society of Plastics Engineers. [source] Hyperbranched polymers in cationic photopolymerization of epoxy systemsPOLYMER ENGINEERING & SCIENCE, Issue 8 2003M. Sangermano Mixtures of epoxy resins in the presence of epoxy hyperbranched polymers (HBP), in the range of 5,15 wt%, were investigated in the cationic photocuring process. No significant differences in rate of polymerization or final epoxy groups conversion were observed. At low concentration, HBP acts as plasticizer and causes a decrease of the glass transition temperature of the epoxy matrix and of the E, value. At higher concentration (about 15 wt%), two Tg values are evident, indicating a biphasic structure of the system. The SEM analysis of the fracture surface of the samples confirms a particulate structure with separate HBP domains interconnected to the epoxy matrix. In all the samples investigated, a clear increase of the impact resistance was observed, resulting either from the plasticization effect or from the particulate structure induced by the presence of the HBP resin. [source] Flexibility improvement of epoxy resin by liquid rubber modificationPOLYMER INTERNATIONAL, Issue 9 2002C Kaynak Abstract The objective of this study was to improve the flexibility of diglycidyl ether of bisphenol-A based epoxy resin by using a liquid rubber. For this purpose, hydroxyl terminated polybutadiene (HTPB) was used at two concentrations of 1,% and 1.5,% by weight. In order to improve compatibility between liquid rubber and epoxy, a silane coupling agent (SCA) was also used. Bending test specimens were moulded by using four different orders of mixing of HTPB with SCA and hardener to investigate the compatibility of HTPB and epoxy matrix. Three-point bending tests indicated that the specimens containing HTPB rubber had higher flexibility than neat epoxy specimens. Moreover, liquid rubber modification resulted in increased plastic strain at failure due to the possible decrease in crosslinking density with the change in reactions path. Fractographic examinations under scanning electron microscope indicated the formation of rubber domains in the epoxy matrix. The deformed rubber domains and increased incidence of deformation lines, especially in the third and fourth group specimens, assessed the improvement in flexibility. © 2002 Society of Chemical Industry [source] Thermally reversible materials based on thermosetting systems modified with polymer dispersed liquid crystals for optoelectronic application,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2006A. Tercjak Abstract The main aim of this research was the generation of new intelligent materials, in this case thermoreversible material, based on an epoxy matrix modified with liquid crystal for optoelectronic application. The samples were prepared by the reaction-induced phase separation (RIPS) of a solution of 4,-(hexyloxy)-4-biphenyl-carbonitrile (HOBC) and polystyrene (PS) in diglicydylether of bisphenol-A epoxy resin (DGEBA). The systems were cured with a stoichiometric amount of an aromatic amine hardener, 4,4,-methylene bis(3-chloro-2,6-diethylaniline) (MCDEA). Taken into account results obtained by differential scanning calorimetry (DSC) and transmission optical microscopy (TOM) equipped with a hot stage it was found that depending on morphology generated by RIPS of HOBC/thermoplastic particles in the epoxy matrix thermally reversible light scattering (TRLS) material can be obtained. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||