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Mauri, Massimiliano, Leo Svenningsson, Thomas Hjertberg, Lars Nordstierna, Oscar Prieto i Christian Müller. "Orange is the new white: rapid curing of an ethylene-glycidyl methacrylate copolymer with a Ti-bisphenolate type catalyst". Polymer Chemistry 9, nr 13 (2018): 1710–18. http://dx.doi.org/10.1039/c7py01840a.
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Vidhi, Ankita, Anu i A. S. Rao. "Spectroscopic characterizations of Dy3+ ions doped phosphate glasses for epoxy-free white LED applications". Optical Materials 132 (październik 2022): 112863. http://dx.doi.org/10.1016/j.optmat.2022.112863.
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OKYERE, Mavis Sika, Lucas Nana Wiredu DAMOAH, Emmanuel NYANKSON i David Sasu KONADU. "SYNERGETIC EFFECT OF A DRAG REDUCER AND PIPELINE INTERNAL COATING ON CAPACITY ENHANCEMENT IN OIL AND GAS PIPELINES: A CASE STUDY". European Journal of Materials Science and Engineering 7, nr 3 (20.09.2022): 195–210. http://dx.doi.org/10.36868/ejmse.2022.07.03.195.
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A case study of a 20-inch diameter gas transmission pipeline assesses theoretically how the synergetic use of pipeline internal coating and drag reducing agent increases the flow rate of a pipeline and its impact on the pipe internal friction. The American Gas Association (AGA) equation and Modified Colebrook-White equations were both used to estimate the capacity of the pipeline in its existing state, after internally coating and after injecting a drag reducing agent in the internally coated pipeline. By means of both AGA equations and Modified Colebrook–White equations, it was observed that Internal coating with surface roughness of 0.0045mm can increase the pipeline capacity (flowrate) by up to 22% for gas pipeline systems. Also, the synergetic use of a pipeline internal coating such as polyamide epoxy or solvent free epoxy and a Polyacrylamide drag reducing agent can increase the pipeline capacity (throughput) above 115.53% for GNGC gas pipeline systems. The analysis shows that synergetic use of internal coatings and drag reducers increases the capacity of gas pipelines and is economically justified with a typical payback period of three years.
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Purdy-Ramos, S. I., E. E. Van Niel, M. S. Forbes i R. M. Carey. "Use of conventional embedment procedures for post-embedding immunocytochemistry of secretory proteins". Proceedings, annual meeting, Electron Microscopy Society of America 47 (6.08.1989): 1052–53. http://dx.doi.org/10.1017/s0424820100157243.
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The methodology of post-embedding immunocytochemistry commonly employs regimens that are more technically difficult than conventional processing and staining of specimens for transmission electron microscopy. Among these regimens are the preparation of frozen thin sections and embedment in hydrophilic acrylic resins such as Lowicryl and LR White . Cryotechnology, however, requires special equipment and exacting preparation of specimens. Use of water-soluble resins likewise demands special care; for example, embedment in LR White involves titrating the dehydration solutions and maintaining oxygen-free curing conditions (usually in gelatin capsules, making selected orientation of specimens quite difficult). It is commonly supposed that conventional treatments such as exposure to osmium tetroxide and uranyl acetate en bloc, with subsequent embedment in epoxy resins, are detrimental to antigenicity.Uranyl acetate block-staining can actually enhance immunocytocheinical staining of some epitopes . Though osmicated tissues have also been successfully immunostained , it is standard procedure first to treat the thin sections on grid with an oxidizing agent such sodium metaperiodate . We have found that a polyclonal antibody to renin effectively immunostains globular inclusions (granules) in juxtaglomerular (JG) cells of rat kidney. This can be accomplished both in unosmicated tissue embedded in LR White (Fig. 1) or in specimens (either intact kidney or isolated JG cells) that have been osmicated, uranyl acetate block- stained, dehydrated through 100% ethanol, and embedded in Poly/Bed epoxy resin (cured at 60 °C). Thin sections were collected on nickel grids and immunostained with Protein A-gold, without prior oxidation to remove osmium (Fig. 1). There are several distinct advantages of using the latter immunocytochemical procedure. First, tissues can be processed in a routine manner; in addition, specific orientation of specimens can easily be accomplished. Furthermore, curing of the embedment does not have to be carried out at low temperatures or in oxygen-free containers; this is particularly useful when processing cultured cells (Fig. 1).
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Serrano, Erik, i Bertil Enquist. "Contact-free measurement and non-linear finite element analyses of strain distribution along wood adhesive bonds". Holzforschung 59, nr 6 (1.11.2005): 641–46. http://dx.doi.org/10.1515/hf.2005.103.
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Abstract The strain distribution along wood adhesive bonds was studied using a contact-free measurement system based on a white-light digital image correlation (DIC) technique. Two different specimen geometries and three different adhesives were investigated. The specimen geometries were according to the standards EN302-1 and ASTM D905. The adhesives tested were a phenolic resorcinol (PRF), a one-component polyurethane (PUR) and an epoxy (EPX). In addition to the experimental investigation, a finite element study using a non-linear fracture mechanics model for the adhesive bond line was carried out, aimed at investigating whether deformation measurements could predict differences in the mechanical behaviour of the adhesives. The measurement technique was found to be capable of distinguishing, in terms of their strain distributions at a given load, adhesives that differed markedly from one another. For example, the brittle PRF adhesive showed more localised strains than the more ductile EPX and PUR adhesives did at the same load level. Another conclusion from this study is that the measurement technique used is applicable to situations in which large strains occur. Thus, the technique used here is of great interest for use in the calibration of finite element models and constitutive theories and for the design of test set-ups.
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Baltić, Marija, Miloš Vorkapić, Milica Ivanović, Dragoljub Tanović i Ivana Mladenović. "Modal analysis of composite plates: Digital image correlation method application". Tribology and Materials 2, nr 2 (lipiec 2023): 62–67. http://dx.doi.org/10.46793/tribomat.2023.010.
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Composite materials and structures are widely used and applied in many industries owing to their advantages, such as satisfactory stiffness-to-mass ratio and corrosion resistance. However, during their operating life, responsible parts subject to complex loads may change and their properties might deteriorate. To ensure structural integrity it is necessary to monitor and regularly check the performance of composite structures. This paper investigates the change of frequency characteristics of two rectangular composite (carbon-epoxy) plates after inflicting structural damage. Following the necessary preparation of the structure's upper surfaces by white-and-black stochastic pattern, the responses (free vibratory movement) of structures to momentary excitation were recorded by an optical, contactless 3D digital image correlation (DIC) system that contains a set of ultrafast cameras. In order to determine the natural frequencies of the plates, the recorded time-domain responses were post-processed, i.e. converted to the frequency domain by fast Fourier transform (FFT). The reduction in values of natural frequencies is observed on the damaged structures. The performed experiments demonstrate the applicability of the DIC method in the structural health monitoring of composite parts.
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Elsafi, Mohamed, Nouf Almousa, Fahad I. Almasoud, Mansour Almurayshid, Amjad R. Alyahyawi i M. I. Sayyed. "A Novel Epoxy Resin-Based Composite with Zirconium and Boron Oxides: An Investigation of Photon Attenuation". Crystals 12, nr 10 (27.09.2022): 1370. http://dx.doi.org/10.3390/cryst12101370.
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We have attempted to develop the gamma radiation shielding abilities of newly prepared epoxy composites by introducing ZrO2. The radiation shielding parameters are experimentally reported below. The experimental setup included an HPGe detector and different radioactive point sources which emitted photons with energies of 0.06, 0.662, 1.173, and 1.333 MeV. The gamma radiation shielding abilities of the epoxy composites were examined in the context of the linear attenuation coefficient (LAC), half-value layer (HVL), radiation absorption ratio, and other factors. The experimental and Phy-X results for the LAC were compared, and acceptable consistency was reported. The lowest LAC values were reported for EBZr-0 (free of ZrO2), and we found that the photon attenuation competence of the present epoxy improved as a result of increasing the ZrO2 content. We compared the LAC values for the present epoxy composites with other samples, and we found that the prepared composites with 20% to 40% ZrO2 had higher LAC values than epoxy with 30% Yahyali Stone. The HVL lengths of the epoxy composites reduced with the addition of ZrO2 for the four selected energies, which confirmed that introducing ZrO2 improves the radiation absorption abilities of epoxy composites. At 0.06 MeV, the HVL for the ZrO2-free epoxy was 2.60 cm, which fell to 0.23 cm after adding 40% ZrO2. The mean free path (MFP) for the prepared composites was less than 1 cm at 0.06 MeV (standard for EBZr-0), while it was 1.32 cm for EBZr-10. For the other energies, it was higher than 6 cm, and became higher than 10 cm at 1.333 MeV for all composites. The obtained results suggest that non-toxic, natural, and cheap epoxy composites with high ZrO2 content have the potential to improve the gamma ray shielding competence of epoxy composites for low energy radiation applications.
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Zhang, Li Juan, Chen Bo Wu, Fei Yang, Xiao Yi Geng, Meng Qian Li i Ji Jun Xiao. "Preparation and Characterization of UV Curable Hybrid System Based on Free Radical and Cationic Mechanism". Applied Mechanics and Materials 470 (grudzień 2013): 141–45. http://dx.doi.org/10.4028/www.scientific.net/amm.470.141.
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A UV curable hybrid system with a dual mechanism of radical and cationic photo-polymerization, was investigated. A kind of free radical oligomer with low viscosity named hexahydrophthalic acid diglycidyl acrylate was first synthesized. The structure of the oligomer was characterization by FTIR. The UV curing processing of hybrid system was traced by real-time FTIR, and compared with free radical, cationic system. Thermal decomposition temperature and glass transition temperature of UV curing film for various system were determined by thermogravimetric analysis (TGA) and differental scanning calorimetry (DSC), respectively. And physical and mechanical properties of those curing films were analyzed and compared. The results show that the radical polymerization of double bond and cationic polymerization of epoxy group could occur simultaneously in hybrid system. The conversion rate of epoxy group for hybrid system was higher than that of epoxy group for cationic system, which demonstrated that the cationic photo-initiator (DPI·PF6) can be sensitized by the free radical photo-initiator (Irgacure 184). Compared with free radical and cationic system, the hardness and mechanical properties of hybrid system curing film were better than those of the cationic system curing film, while closed to those of free radical system.
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Zheng, Xiao Ling, Min You, Yong Zheng, Hai Zhou Yu i Chun Mei Yang. "Testing and Analysis of the Inner Stress in Adhesive Coating Layer Using Strain Gauges and Finite Element Method". Materials Science Forum 490-491 (lipiec 2005): 667–71. http://dx.doi.org/10.4028/www.scientific.net/msf.490-491.667.
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The residual stress in epoxy adhesive layer deposited on metal and other substrate at room temperature is studied. With embedded strain gauges in arranged depth of epoxy layer, the strain changes in the adhesive layer induced by the curing procedure and the changes of ambient temperature were measured to evaluate the changes of residual stress in place during a period after the curing procedure finished. The actual strain in epoxy adhesive layer from curing is used to estimate the residual stresses in it. While taking the strain obtained from the surface of the adhesive layer as free strain, the residual stress can be calculated and presented a strongly cyclic variation with a period of 24 h. The inner stress is also analyzed using the finite element method.
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Netkueakul, Woranan, Beatrice Fischer, Christian Walder, Frank Nüesch, Marcel Rees, Milijana Jovic, Sabyasachi Gaan, Peter Jacob i Jing Wang. "Effects of Combining Graphene Nanoplatelet and Phosphorous Flame Retardant as Additives on Mechanical Properties and Flame Retardancy of Epoxy Nanocomposite". Polymers 12, nr 10 (14.10.2020): 2349. http://dx.doi.org/10.3390/polym12102349.
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The effects of combining 0.1–5 wt % graphene nanoplatelet (GNP) and 3–30 wt % phosphorous flame retardant, 9,10- dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as fillers in epoxy polymer on the mechanical, flame retardancy, and electrical properties of the epoxy nanocomposites was investigated. GNP was homogeneously dispersed into the epoxy matrix using a solvent-free three-roll milling process, while DOPO was incorporated into the epoxy resin by mechanical stirring at elevated temperature. The incorporation of DOPO reduced the crosslinking density of the epoxy resin. When using polyetheramine as a hardener, the structural rigidity effect of DOPO overshadowed the crosslinking effect and governed the flexural moduli of epoxy/DOPO resins. The flexural moduli of the nanocomposites were improved by adding GNP up to 5 wt % and DOPO up to 30 wt %, whereas the flexural strengths deteriorated when the GNP and DOPO loading were higher than 1 wt % and 10 wt %, respectively. Limited by the adverse effects on mechanical property, the loading combinations of GNP and DOPO within the range of 0–1 wt % and 0–10 wt %, respectively, in epoxy resin were further studied. Flame retardancy index (FRI), which depended on three parameters obtained from cone calorimetry, was considered to evaluate the flame retardancy of the epoxy composites. DOPO showed better performance than GNP as the flame retardant additive, while combining DOPO and GNP could further improve FRI to some extent. With the combination of 0.5 wt % GNP and 10 wt % DOPO, improvement in both mechanical properties and flame retardant efficiency of the nanocomposite was observed. Such a combination did not affect the electrical conductivity of the nanocomposites since the percolation threshold was at 1.6 wt % GNP. Our results enhance the understanding of the structure–property relationship of additive-filled epoxy resin composites and serve as a property constraining guidance for the composite manufacturing.
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Wang, Jun Jun, Bo Wang, Wei Zhou, Jing Gong, Zhen Li Gong i Shao Jie Yue. "Investigation of Free Volume in Epoxy Resins Studied by PALS". Materials Science Forum 607 (listopad 2008): 82–84. http://dx.doi.org/10.4028/www.scientific.net/msf.607.82.
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The influences of curing agents and the water absorption on the microstructure have been studied by positron annihilation lifetime spectroscopy (PALS) and gravimetric measurement for epoxy resins DER331 (E51). We found that the o-Ps lifetime 3τ dramatically decreases with the immersion time from 0h to 6h, and then reaches a saturate level in higher water absorption, while the o-Ps intensity almost remains a constant for all samples. This fact indicated that the water was first filled into free volume holes at low water content. The observation of the constant of I3 suggested that the free volume concentration was not affected by the water sorption. Experimental results indicated that both chemical reaction between the positronium and chlorines and electronegative chlorines attracting positrons can reduce the positronium formation.
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Zhao, Ruikang, Zhanping Zhang i Yuhong Qi. "Influence of Epoxy Content on the Properties and Marine Bacterial Adhesion of Epoxy Modified Silicone Coatings". Coatings 10, nr 2 (2.02.2020): 126. http://dx.doi.org/10.3390/coatings10020126.
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This study addresses the issue of enhancing the mechanical properties and adhesion of silicone antifouling coatings. In this paper, γ-aminopropyltriethoxysilane was used to pretreat bisphenol A epoxy resin to obtain epoxy-silicone prepolymer, which was then mixed with hydroxyl-terminated polydimethylsiloxane to obtain epoxy-modified silicone. It was cured with polyamide curing agent and dibutyltin dilaurate catalyst to form film, and a three-component epoxy-modified silicone coating was prepared. Fourier transform infrared (FTIR) spectroscopy was used to characterize its chemical structure. The effects of epoxy content on the surface properties, mechanical properties and antibacterial properties of the coatings were characterized by confocal laser scanning microscope (CLSM), contact angle measurements, tensile test and bacterial adhesion test. The results show that adding epoxy makes the adhesion of the coating at level 1 and the surface free energy of the coating was between 15–21 mJ/m2. When its content is less than 22.1 wt %, the coating is in a ductile material state. Once it is higher than 22.1 wt %, the coating was in a brittle material state. As the content increases, material’s hardness and fracture strength increases; elastic modulus decreases first and then increases, but bacteria removal rate decreases. The modification of the epoxy to silicone can effectively improve the adhesion and mechanical properties of the coating, while maintaining the characteristics of the low surface of the coating. It plays a positive role in improving the performance of silicone antifouling coatings.
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Wang, Bin, Dihui Li, Guijun Xian i Chenggao Li. "Effect of Immersion in Water or Alkali Solution on the Structures and Properties of Epoxy Resin". Polymers 13, nr 12 (8.06.2021): 1902. http://dx.doi.org/10.3390/polym13121902.
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The durability of fiber-reinforced polymer (FRP) composites is significantly dependent on the structures and properties of the resin matrix. In the present paper, the effects of physical or chemical interactions between the molecular chain of the epoxy resin matrix and water molecules or alkaline groups on the water absorption, mechanical structures, and microstructures of epoxy resin samples were studied experimentally. The results showed that the water uptake curves of the epoxy resin immersed in water and an alkali solution over time presented a three-stage variation. At different immersion stages, the water uptake behavior of the resin showed unique characteristics owing to the coupling effects of the solution concentration gradient diffusion, molecular hydrolysis reaction, and molecular segment movement. In comparison with the water immersion, the alkali solution environment promoted the hydrolysis reaction of the epoxy resin molecular chain. After the immersion in water or the alkali solution for one month, the water uptake of the resin was close to saturate, and the viscoelasticity was observed to decrease significantly. The micropore and free volume space on the surface and in the interior of the resin gradually increased, while the original large-scale free volume space decreased. The tensile strength decreased to the lowest point after the immersion in water and the alkali solution for one month, and the decrease percentages at 20 °C and 60 °C water or 60 °C alkali solution were 24%, 28%, and 22%, respectively. Afterward, the tensile strength recovered with the further extension of immersion time. In addition, it can be found that the effect of the alkali solution and water on the tensile strength of the epoxy resin was basically the same.
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Szołyga, Mariusz, Michał Dutkiewicz, Marek Nowicki, Kamila Sałasińska, Maciej Celiński i Bogdan Marciniec. "Phosphorus-Containing Silsesquioxane Derivatives as Additive or Reactive Components of Epoxy Resins". Materials 13, nr 23 (26.11.2020): 5373. http://dx.doi.org/10.3390/ma13235373.
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Two phosphorus-containing cage-like silsesquioxane derivatives were synthesized as reactive or additive flame retardants for epoxy resin. The silsesquioxanes were obtained via an epoxide ring-opening reaction using a 10-hydroxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPA). In one derivative containing in its structure 4 glycidoxypropyl and 4 phosphate groups, denoted as 4P4GS, only half of the epoxy rings was reacted with phosphate to obtain a reactive additive, while in the second derivative containing 8 phosphate groups, denoted as 8PS, all epoxy groups were converted, thus an additive modifier was obtained. The silsesquioxanes containing phosphorus atoms and the reactive phosphorus-free silsesquioxane derivative (octakis[(3-glycidoxypropyl)dimethylsiloxy]octasilsesquioxane (8GS)) were used to prepare hybrid materials based on epoxy resin. To compare the impact of the structure of silsesquioxane derivatives on the properties of hybrid materials, a number of samples containing 1, 5, and 10% of the modifiers making a series of epoxy materials containing additive or reactive modifiers, were obtained. The modified epoxies were studied using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), nanoindentation, water contact angle, and cone calorimetry tests to assess the effects of the modifier structure on the physicochemical properties of the investigated materials.
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Abdelmola, Fatmaelzahraa, i Leif A. Carlsson. "State of water in void-free and void-containing epoxy specimens". Journal of Reinforced Plastics and Composites 38, nr 12 (26.02.2019): 556–66. http://dx.doi.org/10.1177/0731684419833469.
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The effect of voids on the state of water absorbed in epoxy has been examined using differential scanning calorimetric analysis for a range of void contents (0 to 50%). For void-free specimens, water absorbed is classified as bound water (nonfreezing). Analysis of the medium and high void content specimens revealed water absorbed in three states: free water, freezable bound water, and nonfreezable bound water. The differential scanning calorimetric results show that the proportions of free water and freezable bound water increase with increasing void content, while the content of nonfreezable bound water decreased. Moisture-induced swelling decreased with increasing void content. The swelling is attributed to the content of nonfreezable bound water as determined by differential scanning calorimetric analysis.
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Li, Bowen, Jianzhong Chen, Yong Lv, Li Huang i Xiaoyu Zhang. "Influence of Humidity on Fatigue Performance of CFRP: A Molecular Simulation". Polymers 13, nr 1 (31.12.2020): 140. http://dx.doi.org/10.3390/polym13010140.
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The study on durability of carbon fiber reinforced plastics (CFRP) in complex environments is critical because of its wide applications. Herein, mechanical behavior of carbon fiber reinforced epoxy composites in the fatigue process were investigated under different humidity via molecular dynamics (MD) simulation method. Transversely isotropic atom based models were established to simulate the structure of CFRP at the atomistic level. Owing to the weak performance in vertical fiber direction, mechanical behavior in a 90° orientation was investigated. Mean stress and energy were both employed to describe the evolution of mechanical performance while mean squared displacement (MSD), radius of gyration (Rg), and free volume were performed to describe the evolution of structural change during the fatigue process. The results show that the humidity led to a weakened interfacial adhesive performance. Free volume became larger under cyclic load, which caused the water molecules to diffuse into the inside of epoxy resin. The distance between the matrix and fiber became larger in the dry system while it reduced because of the diffusion of water molecules in wet system. The rate of performance degradation decreased with the increase in humidity because of poor initial performance at high humidity.
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Monetta, T., A. Acquesta, A. Carangelo i F. Bellucci. "The Effect of Graphene on the Protective Properties of Water-Based Epoxy Coatings on Al2024-T3". International Journal of Corrosion 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/1541267.
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0.5 and 1% wt. of graphene nanoflakes were added to an anticorrosive additives-free water-based epoxy resin applied to Al2024-T3 samples. Calorimetric (DSC) and adhesion (cross-cut test) tests indicated that the presence of graphene did not affect the polymerization process of the resin or its adhesion to the substrate while it had some effect on its wettability. Electrochemical Impedance Spectroscopy (EIS) results obtained suggested that the addition of a small amount of graphene greatly enhanced the protective properties of the epoxy coating, retarding electrolytes absorption and reducing the total amount of adsorbed water. The latter occurrence suggests that the graphene effect on coating performances is related to both extended diffusion pathway length and graphene/matrix interaction due to the unique properties of graphene.
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Yahya, Khaled W., i Edrees E. Khadeer. "Study the Effect of Weight Fractions of Different Powders on the Attenuation Performances of the Epoxy Composite". NeuroQuantology 19, nr 9 (12.10.2021): 142–51. http://dx.doi.org/10.14704/nq.2021.19.9.nq21147.
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Among all types of radiation, X-ray has always garnered the most interest, owing to the growing availability of X-ray tubes in industry, research institutions, and medical facilities. In this research, the linear (μl) and mass (μm) attenuation coefficient, half value layer (HVL) and mean free path (λ) of the epoxy polymer-based composites which includes both lead oxide (Pb3O4), mixture of (Fe2O3 + Pb3O4) and barium sulfate (BaSO4) with different weight percentages were determined experimentally for the incident photon energies of (29-35 kV) emitted from (X-rays) source. The dispersion of the filler was also investigated using a scanning electron microscope to examine the composites morphology. The obtained results showed that adding these powders to epoxy has an effect on the X-ray shielding abilities of the prepared composites, meaning that there is a direct relationship between the weight ratios of the composite material with the linear (μl) and mass (μm) attenuation coefficient, and an inverse relationship with the half value layer (HVL) and free path rate (λ). While changing the X-ray shield with applied voltages showed a behavior opposite to what was mentioned above. The result also shows that the lead oxide (Pb3O4) composites yield better attenuation performance than the pure epoxy and the other two composites, especially at high weight fraction (50 Wt.%) of this filler, which due to the high density of these fillers and fine dispensability in the polymer matrix.
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Shan, Junyang, Zijun Yang, Guoguang Chen, Yang Hu, Ying Luo, Xianming Dong, Wenxu Zheng i Wuyi Zhou. "Design and Synthesis of Free-Radical/Cationic Photosensitive Resin Applied for 3D Printer with Liquid Crystal Display (LCD) Irradiation". Polymers 12, nr 6 (15.06.2020): 1346. http://dx.doi.org/10.3390/polym12061346.
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In this work, aiming at a UV-curing 3D printing process with liquid crystal display (LCD) irradiation, a novel free-radical/cationic hybrid photosensitive resin was designed and prepared. After testing, the results showed that the acrylate monomers could be polymerized through a free-radical mechanism, while the epoxides were polymerized by a cationic curing mechanism. During the process of UV-curing, the acrylate and epoxide polymers were crosslinked and further locked together by non-covalent bonds. Therefore, an interpenetrating polymer network (IPN) structure could be formed through light-curing 3D-printing processes. Fourier transform infrared spectroscopy (FT-IR) revealed that the 3,4-epoxy cyclohexyl methyl-3,4-epoxy cyclohexyl formate and acrylic resin were both successfully involved in the UV-curing process. Furthermore, in order to make the 3D-printed objects cured completely, post-processing was of great importance. The results from the systematic study of the dynamic mechanical properties of the printed objects showed that the heating treatment process after UV irradiation was very necessary and favorable for the complete cationic polymerization of UV-6110 induced by Irgacure 261. The optimum heating treatment conditions were achieved at a temperature of 70 °C for 3 h.
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Elfarhani, Makram, Fethi Guesmi, Ali Mkaddem, Sami Ghazali, Saeed Rubaiee i Abdessalem Jarraya. "Thermal Aspects in Edge Trimming of Bio-Filled GFRP: Influence of Fiber Orientation and Silica Sand Filler in Heat Generation". Materials 15, nr 14 (8.07.2022): 4792. http://dx.doi.org/10.3390/ma15144792.
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The present work aims to determine the influence of Glass Fiber-Reinforced Polymer (GFRP) laminating configuration in heat generation during the dry edge trimming process. Temperature measurement experiments were conducted on pure epoxy matrix, 15% unidirectional glass fiber reinforced epoxy, and 28% silica sand-filled GFRP specimens through eight type-K thermocouples evenly distributed along the trim plans and connected to a data acquisition system. Infrared thermographic measurements were also conducted to investigate the tool temperature evolution while processing. It was found that perpendicular fiber edge milling induces a sharp increase with peak temperature measurements reaching 119 °C, while machining parallel to fiber leads to a maximum temperature history of 41 °C, which is very close to that obtained from the pure epoxy test. It was also found that the addition of silica sand grains in the GFRP matrix reduces both tool and specimen temperature magnitudes up to 67% for 90° plies and 14% for 0° plies compared to silica sand-free composite initial values. The heat partition was calculated from the measured (electric) and estimated energies for the tool, the workpiece, and chips, respectively. It appears from predictions that the addition of silica sand grains increases the heat conductivity of the GFRP materials (with rates of 20% for 0° fiber orientation and 10% for 90° fiber direction), while it reduces that conducted to the milling tool. Scanning Electron Microscopy (SEM) inspections helped detect the dominating machining defects relative to each GFRP configuration and explained the heat generation and dissipation effects in light of peak temperature measurements.
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Pan, Shengqi, Jigang Feng, Babak Safaei, Zhaoye Qin, Fulei Chu i David Hui. "A comparative experimental study on damping properties of epoxy nanocomposite beams reinforced with carbon nanotubes and graphene nanoplatelets". Nanotechnology Reviews 11, nr 1 (1.01.2022): 1658–69. http://dx.doi.org/10.1515/ntrev-2022-0107.
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Abstract Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) are extremely ideal nanofillers for applications in damping polymer. This work explores the damping behavior of polymer nanocomposite beams made of epoxy resin reinforced with CNTs and GNPs experimentally. Beam specimens for the vibration tests together with dynamic mechanical analysis (DMA) are fabricated with different weight ratios of CNTs and GNPs, upon which DMA and free vibration tests are conducted. Scanning electron microscope images are also obtained to check the dispersion of nanofillers in microscale. It is found that the first-order loss factor of composite beam specimens shows a rise of 41.1% at 0.4 wt% CNT content compared with that of pure epoxy, while the first-order loss factor of composite beam specimens with 0.025 wt% GNP content increases up by 128.9%. The maximum value of the first-order loss factor of nanocomposite beams with GNP reinforcement is 62.2% higher than that with CNTs.
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Mirmanto, M., S. Sugiman, F. Fathurrahman i M. D. Ramadhani. "Konduktivitas termal komposit resin epoksi dan serbuk arang tempurung kelapa". Dinamika Teknik Mesin 12, nr 1 (1.04.2022): 29. http://dx.doi.org/10.29303/dtm.v12i1.502.
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Composite materials are materials that are widely developed and their use has been widespread in various industrial and household sectors. Epoxy composites filled with coconut shell charcoal powder have been tested for their thermal conductivity properties using the one-dimensional conduction method. The tested specimens had dimensions of 50 mm x 50 mm x 5 mm made of epoxy and coconut shell powder with a percentage of charcoal weight of 0%, 10%, 20% and 30%. The specimen is inserted into a thermal conductivity measuring instrument made of solid aluminum which is insulated around it. The heater is mounted on the aluminum as a heat source, while the other end is left open to the free air in the room. The results showed that the highest average thermal conductivity was a 30% variation of 0.5003 W/m°C, then a 20% variation of 0.3738 W/m°C, a 10% variation of 0.3487 W/m°C. and the lowest at 0% variation without using coconut shell charcoal powder at 0.1364 W/m°C.
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Riahipour, Ramin, Abolfazl Alizadeh Sahraei, Nekoda van de Werken, Mehran Tehrani, Karen Abrinia i Majid Baniassadi. "Improving flame-retardant, thermal, and mechanical properties of an epoxy using halogen-free fillers". Science and Engineering of Composite Materials 25, nr 5 (25.09.2018): 939–46. http://dx.doi.org/10.1515/secm-2017-0131.
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AbstractVarious nano- and micro-sized fillers can be integrated into polymers to enhance their flame-retardant performance. In this work, a diglycidyl-ether bisphenol A epoxy was used as the matrix and nanostructured silica aerogel (AG) and ammonium polyphosphate (APP) microparticles were investigated as fillers to improve the flame-retardant and thermal properties of the epoxy. The anti-flame, thermal, and mechanical properties of the composites were investigated for different volume fractions of filler particles. It was found that APP decreased the burning rate while significantly improving the thermal stability. To investigate the flame resistant properties of combined AG and APP, an optimized ratio of AG and APP was added to the epoxy, leading to a stable flame-retardant epoxy with a low thermal conductivity and improved glass transition temperature (Tg). The synergy between the AG and APP in composite samples resulted in an interesting burning behavior where sample core was relatively less deteriorated compared with the samples containing only APP or AG. This was attributed to the decrease of thermal conductivity due to the addition of AG. Lastly, samples containing APP showed the highest limiting oxygen index percentage and it was found that only small amounts of APP are required to make the epoxy flame-retardant.
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Zhu, Zhiqiang, Erbing Zhang, Yijing Tu, Manyu Ye i Nairong Chen. "An Eco-Friendly Wood Adhesive Consisting of Soybean Protein and Cardanol-Based Epoxy for Wood Based Composites". Polymers 14, nr 14 (12.07.2022): 2831. http://dx.doi.org/10.3390/polym14142831.
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Formaldehyde-derived wood adhesives have dominated in woody composites production up to now, while facing a significant challenge in non-renewable raw materials and the formaldehyde emission. To solve these problems, an eco-friendly soybean protein-based wood adhesive was explored via the addition of renewable cardanol based epoxy (CBE) as cross-linking agent. The curing mechanism and viscosity of the adhesives were investigated and the bonding performance was evaluated with three-ply plywood. Fourier transformed infrared spectroscopy (FTIR) analysis confirmed the formation of new ether linkages and the consumption of epoxy groups in the cured adhesives, thereby improving the thermal stabilities and cohesion. Plywood bonded with the CBE-modified soybean protein-based adhesive reached the maximum wet shear strength of 1.11 MPa (4 wt.% CBE addition), a 48% increase compared to the control, whereas the viscosity of adhesive decreased by 68.2%. The wet shear strength of the plywood met the requirements of the Chinese National Standard GB/T 9846-2015 for interior plywood application. The formaldehyde-free adhesive with excellent water resistance adhesiveness performance shows great potential in woody composites as an alternative to formaldehyde derived wood adhesives.
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Shi, Jiangjing, Yanping Zou, Wenfu Zhang i Hong Chen. "Effects of the molding process on properties of bamboo fiber/epoxy resin composites". BioResources 16, nr 4 (20.09.2021): 7416–27. http://dx.doi.org/10.15376/biores.16.4.7416-7427.
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Filament winding is an advanced technology for fabrication of high-performance composites. Pressure-free fabrication can be achieved for non-planar composites with complicated shapes using resin-immersed twisting fibers. In this study, twisted bamboo fiber (TBF) composites were prepared by a filament winding processing (FWP). Short bamboo fiber (SBF), long bamboo fiber (LBF), and TBF composites were prepared by hot pressing (HP) and resin transfer molding (RTM). The results showed that the bamboo fiber/epoxy resin composites were positively related to the fiber size. The bamboo fiber/epoxy resin composites fabricated by FWP exhibited optimal shear performance, while those generated by RTM exhibited optimized bending performance. Dynamic thermomechanical analysis revealed that composites made by FWP had optimized interfaces. The FWP mechanism of bamboo fiber composites was resin immersion and alignment of TBF; upon resin immersion the TBF were coated by resin and could not enter the internal tubes or parenchyma tissues of the TBF. The TBF was aligned by winding equipment. After heated solidification of the resin, several bubble pores were distributed on both sides of the TBF, whose positions remained static over time. The filament winding processing for bamboo fiber composites enhanced their performance and could lead to the applications in bamboo fibers composites.
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Khalili, Pooria, Kim Yeow Tshai, Ing Kong i Chin Hooi Yeoh. "The Effects of Graphene and Flame Retardants on Flammability and Mechanical Properties of Natural Fibre Reinforced Polymer Composites". Key Engineering Materials 701 (lipiec 2016): 286–90. http://dx.doi.org/10.4028/www.scientific.net/kem.701.286.
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The effects of incorporating three different types of flame retardant (FR) and two variants of graphene into 10 %wt palm EFB natural fibre (NF) filled epoxy composites were investigated in term of the flammability, thermal and mechanical properties through standard Bunsen burner experiment, bomb calorimetry, TGA and tensile tests. The types of FR employed include zinc borate (ZB), ammonium polyphosphate (APP) and alumina trihydrate (ATH) while a lab synthesised and a commercial form of graphene were used in the current work. Compared to the neat NF filled epoxy composite, specimens loaded with 15 %wt of either ZB or APP demonstrated a drip-free condition as observed from the Bunsen burner tests, which could be attributed to the strong char forming characteristic of the compositions. In specimens containing 15 %wt of either ZB or ATH, results from Bomb calorimetry revealed that these specific formulations produced the lowest mean gross heat release amongst others, suggesting better resistant to flame. Relative to the graphene incorporated composites, the post TGA measured mass residue was observed to be greater in FR rich formulations, suggesting that FR additives capable of yielding a much superior flame retardancy compared to graphene. While a slight increases in Young’s modulus was recorded in composites loaded with FR, such formulations produced several main drawbacks whereby reduction in ultimate tensile strength and elongation to break were being measured in large proportion of the specimens.
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Yin, Allice Tan Mun, Shayfull Zamree Abd Rahim, Mohd Mustafa Al Bakri Abdullah, Marcin Nabialek, Abdellah El-hadj Abdellah, Allan Rennie, Muhammad Faheem Mohd Tahir i Aurel Mihail Titu. "Potential of New Sustainable Green Geopolymer Metal Composite (GGMC) Material as Mould Insert for Rapid Tooling (RT) in Injection Moulding Process". Materials 16, nr 4 (19.02.2023): 1724. http://dx.doi.org/10.3390/ma16041724.
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The investigation of mould inserts in the injection moulding process using metal epoxy composite (MEC) with pure metal filler particles is gaining popularity among researchers. Therefore, to attain zero emissions, the idea of recycling metal waste from industries and workshops must be investigated (waste free) because metal recycling conserves natural resources while requiring less energy to manufacture new products than virgin raw materials would. The utilisation of metal scrap for rapid tooling (RT) in the injection moulding industry is a fascinating and potentially viable approach. On the other hand, epoxy that can endure high temperatures (>220 °C) is challenging to find and expensive. Meanwhile, industrial scrap from coal-fired power plants can be a precursor to creating geopolymer materials with desired physical and mechanical qualities for RT applications. One intriguing attribute of geopolymer is its ability to endure temperatures up to 1000 °C. Nonetheless, geopolymer has a higher compressive strength of 60–80 MPa (8700–11,600 psi) than epoxy (68.95 MPa) (10,000 psi). Aside from its low cost, geopolymer offers superior resilience to harsh environments and high compressive and flexural strength. This research aims to investigate the possibility of generating a new sustainable material by integrating several types of metals in green geopolymer metal composite (GGMC) mould inserts for RT in the injection moulding process. It is necessary to examine and investigate the optimal formulation of GGMC as mould inserts for RT in the injection moulding process. With less expensive and more ecologically friendly components, the GGMC is expected to be a superior choice as a mould insert for RT. This research substantially impacts environmental preservation, cost reduction, and maintaining and sustaining the metal waste management system. As a result of the lower cost of recycled metals, sectors such as mould-making and machining will profit the most.
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Arif Mat Norman, M., M. Amiruddin Zainuddin i Jamaluddin Mahmud. "The Effect of Various Fiber Orientations and Boundary Conditions on Natural Frequencies of Laminated Composite Beam". International Journal of Engineering & Technology 7, nr 3.11 (21.07.2018): 67. http://dx.doi.org/10.14419/ijet.v7i3.11.15932.
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This paper investigates the free vibration characteristics of laminate composite beam for various lamination schemes and under various boundary conditions. A beam model with the aspect ratio (length to thickness) of 25 to 150 made of carbon/ epoxy laminates under free vibration were constructed using a commercially available finite element software (ANSYS). The varied parameters are the lamination schemes (cross ply, angle ply and unidirectional ply) and boundary conditions (Clamp-Free (C-F), Clamp-Clamp (C-C), Clamp-Hanger (C-H), Free-Free (F-F) and Hanger-Hanger (H-H) ). For each case, finite element simulations were performed and the natural frequencies were determined. Mode shapes were also analyzed to observe the beam’s deformation behavior. Results showed that increasing aspect ratio will decrease natural frequencies for the first seven mode shapes. In terms of lamination scheme, the unidirectional ply produced the highest frequency (34.26 Hz), followed by cross ply (34.05 Hz) and angle ply (13.60 Hz) at the aspect ratio of 25. In terms of boundary conditions, the Hanger-Hanger boundary condition produced the highest natural frequency (2272.52 Hz) at the aspect ratio of 25, while Clamped-Free boundary condition produced the lowest frequency (2.28 Hz) at the aspect ratio of 150. In general, it can be concluded that the current study is useful and has contributed significant knowledge to better understand of effect of various fiber orientations and boundary conditions on the natural frequencies of laminated composite beam.
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Guo, Wenna, Zhiyong Li, Meng Yuan, Geng Chen, Qiao Li, Hui Xu i Xin Yang. "Molecular Insight into Stereoselective ADME Characteristics of C20-24 Epimeric Epoxides of Protopanaxadiol by Docking Analysis". Biomolecules 10, nr 1 (9.01.2020): 112. http://dx.doi.org/10.3390/biom10010112.
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Chirality is a common phenomenon, and it is meaningful to explore interactions between stereoselective bio-macromolecules and chiral small molecules with preclinical and clinical significance. Protopanaxadiol-type ginsenosides are main effective ingredients in ginseng and are prone to biotransformation into a pair of ocotillol C20-24 epoxide epimers, namely, (20S,24S)-epoxy-dammarane-3,12,25-triol (24S-PDQ) and (20S,24R)-epoxy dammarane-3,12,25-triol (24R-PDQ) that display stereoselective fate in vivo. However, possible molecular mechanisms involved are still unclear. The present study aimed to investigate stereoselective ADME (absorption, distribution, metabolism and excretion) characteristics of PDQ epimers based on molecular docking analysis of their interaction with some vital proteins responsible for drug disposal. Homology modeling was performed to obtain 3D-structure of the human isoenzyme UGT1A8, while calculation of docking score and binding free energy and ligand–protein interaction pattern analysis were achieved by using the Schrödinger package. Stereoselective interaction was found for both UGT1A8 and CYP3A4, demonstrating that 24S-PDQ was more susceptible to glucuronidation, whereas 24R-PDQ was more prone to oxidation catalyzed by CYP3A4. However, both epimers displayed similarly strong interaction with P-gp, a protein with energy-dependent drug-pump function, suggesting an effect of the dammarane skeleton but not C-24 stereo-configuration. These findings provide an insight into stereo-selectivity of ginsenosides, as well as a support the rational development of ginseng products.
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Abishera, R., R. Velmurugan i KV Nagendra Gopal. "Free, partial, and fully constrained recovery analysis of cold-programmed shape memory epoxy/carbon nanotube nanocomposites: Experiments and predictions". Journal of Intelligent Material Systems and Structures 29, nr 10 (5.03.2018): 2164–76. http://dx.doi.org/10.1177/1045389x18758187.
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Thermally activated shape memory polymers are typically programmed by initially heating the material above the glass transition temperature ( Tg), deforming to the desired shape, cooling below Tg, and unloading to fix the temporary shape. This process of deforming at high temperatures becomes a time-, labor-, and energy-expensive process while applying to large structures. Alternatively, materials with reversible plasticity shape memory property can be programmed at temperatures well below the glass transition temperature which offers several advantages over conventional programming. Here, the free, partial, and fully constrained recovery analysis of cold-programmed multi-walled carbon nanotube–reinforced epoxy nanocomposites is presented. The free recovery analysis involves heating the temporary shape above Tg without any constraints (zero stress), and for fully constrained recovery analysis, the temporary shape is held constant while heating. The partially constrained recovery behavior is studied by applying a constant stress of 10%, 25%, and 50% of the maximum recovery stress obtained from the completely constrained recovery analysis. The samples are also characterized for their thermal, morphological, and mechanical properties. A non-contact optical strain measurement method is used to measure the strains during cold-programming and shape recovery. The different recovery behaviors are analyzed by using a thermo-viscoelastic–viscoplastic model, and the predictions are compared with the experimental results.
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Panaccione, Paul, Tao Wang, Xu Chen, Susan Luo i Guo-Quan Lu. "Improved Heat Dissipation and Optical Performance of High-Power LED Packaging with Sintered Nanosilver Die-Attach Material". Journal of Microelectronics and Electronic Packaging 7, nr 3 (1.07.2010): 164–68. http://dx.doi.org/10.4071/imaps.264.
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Heat removal in packaged high-power light-emitting diode (LED) chips is critical to device performance and reliability. Thermal performance of LEDs is important in that lowered junction temperatures extend the LED's lifetime at a given pho-tometric flux (brightness). Optionally, lower thermal resistance can enable increased brightness operation without exceeding the maximum allowable Tj for a given lifetime. A significant portion of the junction-to-case thermal resistance comes from the joint between chip and substrate, or the die-attach layer. In this study, we evaluated three different types of leading die-attach materials; silver epoxy, lead-free solder, and an emerging nanosilver paste. Each of the three was processed via their respective physical and chemical mechanisms: epoxy curing by cross-linking of polymer molecules; intermetalic soldering by reflow and solidification; and nanosilver sintering by solid-state atomic diffusion. High-power LED chips with a range of chip areas from 3.9 mm2 to 9.0 mm2 were attached by the three types of materials onto metalized aluminum nitride substrates, wire-bonded, and then tested in an electro-optical setup. The junction-to-heatsink thermal resistance of each LED assembly was determined by the wavelength shift methodology. We found that the average thermal resistance in the chips attached by the nanosilver paste was the lowest, and it was highest from the chips attached by the silver epoxy. For the 3.9 mm2 die, the difference was about 0.6°C/W, while the difference between the sintered and soldered was about 0.3°C/W. The lower thermal resistance in the sintered joints is expected to significantly improve the photometric flux from the device. Simple calculations, excluding high current efficiency droop, predict that the brightness improvement could be as high as 50% for the 3.9 mm2 chip. The samples will be functionally tested at high current, in both steady-state and pulsed operation, to determine brightness improvements, including the impact of droop. Nanosilver die-attach on a range of chip sizes up to 12 mm2 are also considered and discussed.
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Panaccione, Paul, Tao Wang, Guo-Quan Lu, Xu Chen i Susan Luo. "Improved Heat Dissipation and Optical Performance of High-power LED Packaging with Sintered Nanosilver Die-attach Material". Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2010, DPC (1.01.2010): 001585–605. http://dx.doi.org/10.4071/2010dpc-wa44.
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Heat removal in packaged high-power light-emitting diode (LED) chips is critical to device performance and reliability. Thermal performance of LEDs is important in that lowered junction temperatures extend the LED's lifetime at a given photometric flux (brightness). Optionally, lower thermal resistance can enable increased brightness operation without exceeding the maximum allowable Tj for a given lifetime. A significant portion of the junction-to-case thermal resistance comes from the joint between chip and substrate, or the die-attach layer. In this study, we evaluated three different types of leading die-attach materials; silver epoxy, lead-free solder, and an emerging nanosilver paste. Each of the three was processed via their respective physical and chemical mechanisms: epoxy curing by cross-linking of polymer molecules; intermetalic soldering by reflow and solidification; and nanosilver sintering by solid-state atomic diffusion. High-power LED chips with a chip area of 3.9 mm2 were attached by the three types of materials onto metalized aluminum nitride substrates, wire-bonded, and then tested in an electro-optical setup. The junction-to-heatsink thermal resistance of each LED assembly was determined by the wavelength shift methodology, described in detail in this paper. We found that the average thermal resistance in the chips attached by the nanosilver paste was the lowest, and it is the highest from the chips attached by the silver epoxy: the difference between the two was about 0.7°C/W, while the difference between the sintered and soldered was about 0.3°C/W. The lower thermal resistance in the sintered joints is expected to significantly improve the photometric flux from the device. Simple calculations, excluding high current efficiency droop, predict that the brightness improvement could be as high as 50% for the 3.9 mm2 chip. The samples will be functionally tested at high current, in both steady-state and pulsed operation, to determine brightness improvements, including the impact of droop. Nanosilver die-attach on a range of chip sizes up to 12 mm2 are also considered and discussed.
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Tahouneh, Vahid. "An Elasticity Solution for Vibration Analysis of Laminated Plates with Functionally Graded Core Reinforced by Multi-walled Carbon Nanotubes". Periodica Polytechnica Mechanical Engineering 61, nr 4 (20.09.2017): 309. http://dx.doi.org/10.3311/ppme.11254.
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In the present work, vibration characteristics of functionally graded (FG) sandwich rectangular plates reinforced by multiwalled carbon nanotubes (MWCNTs) resting on Pasternak foundation are presented. The response of the elastic medium is formulated by the Winkler/Pasternak model. Modified Halpin-Tsai equation is used to evaluate the Young’s modulus of the MWCNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The mass density and Poisson’s ratio of the MWCNT/phenolic composite are considered based on the rule of mixtures. The proposed sandwich rectangular plates have two opposite edges simply supported, while all possible combinations of free, simply supported and clamped boundary conditions are applied to the other two edges. The effects of two-parameter elastic foundation modulus, geometrical and material parameters together with the boundary conditions on the frequency parameters of the sandwich plates are investigated.
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Głodkowska, W., i M. Ruchwa. "Static Analysis of Reinforced Concrete Beams Strengthened with CFRP Composites/ Analiza Statyczna Belek Zelbetowych Wzmocnionych Tasmami Kompozytowymi". Archives of Civil Engineering 56, nr 2 (1.06.2010): 111–22. http://dx.doi.org/10.2478/v.10169-010-0006-9.
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Abstract This paper presents the possibility to apply numerical simulation in static analysis of reinforced concrete structure strengthened with carbon fibre reinforced polymer composite strips (CFRP). Reinforced concrete beams, with strengthening in form values CFRP made of carbon fibres and epoxy resin, featuring various width, as well as non-strengthened bent beams, were analysed. The simply supported beams arranged in a free support scheme were subjected to two concentrated forces within full range of loading (until collapse). The numerical analysis was performed through application of the Finite Elements Method (FEM), and the calculation model applied took into account the geometric and physical nonlinearity. The problem was solved by application of the quasi-static strategy method of calculations using ABAQUS software. While analysing the results, we focused on the run of changes in structure displacement and development of material damage, up to the point of destruction of the beam
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Elmahdy, Ahmed, Aldobenedetto Zotti, Anna Borriello, Mauro Zarrelli i Patricia Verleysen. "In-Depth Analysis of the High Strain Rate Compressive Behavior of RTM6 Epoxy Using Digital Image Correlation". Polymers 14, nr 9 (27.04.2022): 1771. http://dx.doi.org/10.3390/polym14091771.
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The aim of this paper is to study the effect of strain rate on the compressive behavior of the highly cross-linked RTM6 epoxy resin used in advanced aerospace composites. Dynamic compression tests were performed using a split Hopkinson pressure bar, along with reference quasi-static compression tests, to cover a strain rate range from 0.001 to 1035 s−1. Special attention was paid to the optimization of the test methodologies in order to obtain material data free of bias related to the use of different load introduction techniques and sample geometries over the considered strain rate range. In addition, the use of full-field 3D deformation measurements allowed the validation of traditional test and material assumptions. A novel self-alignment tool was developed to enable perfect interfacial contact during compression loading. The 3D digital image correlation technique was used to measure the instantaneous deformation of the sample during compression at different strain rates. Results showed a pronounced strain rate sensitivity of the RTM6 epoxy in compression. The peak yield strength increased with increasing strain rate, while the elastic modulus and Poisson’s ratio in compression were independent of the strain rate. The barreling of the sample in compression, quantified by the barreling ratio, showed an increase during the progression of the compression tests. However, the barreling ratio significantly decreased with the increasing strain rate. Finally, it was shown that neglecting the significant volume change in the yield stages gave rise to a non-negligible underestimation of the strength of the material.
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Kőszegi, Szilvia, i Éva Dénes. "Paintability of Traditional and Chromium(VI)-Free Conversion Layers on Galvanized Steels". Materials Science Forum 589 (czerwiec 2008): 415–20. http://dx.doi.org/10.4028/www.scientific.net/msf.589.415.
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Continuous hot dip galvanized steel samples have been treated with traditional chromium(VI)-containing passivator and environment friendly rare-earth metal containing ceriumsalt and lanthanum-salt based solutions using different immersion times. The treated surfaces have been examined by scanning electron microscope equipped with an energy dispersive X-ray analyser. After the pre-treatment the samples have been spray-painted with epoxy-based organic paint. The adhesion was tested with bending and cross-cut test. Thereafter salt spray test was performed on duplex systems. After 48 hours samples have been taken out from the corrosion chamber in order to perform electrochemical impedance measurements for 24 hours. Based on the results the most promising passivation among the chromium(VI)-free solutions has been found to be the cerium-salt based treatment. The adhesion of the organic coating was better on cerium-chloride treated substrate than on chromated one, while the anti corrosion properties of the two duplex systems were comparable.
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Shahid, Saleem, G. Guido Gentili, Giancarlo Bernasconi, Hamza Nawaz i Ahsan S. Rana. "Multi-Layer Material Characterization at Ka-Band Using Bayesian Inversion Method". Electronics 12, nr 3 (21.01.2023): 563. http://dx.doi.org/10.3390/electronics12030563.
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This paper presents the implementation of the Bayesian inversion method for the characterization and estimation of different dielectric material properties. The scattering parameters of single and multi-layer materials are measured using a free-space experimental setup using a standard gain horn antenna and a Vector Network Analyzer (VNA) at Ka-band (26–40 GHz). The relative permittivity, material thickness, and material positioning error are defined as model parameters and estimated using the observed (measured) data. The FR4 Epoxy, Rogers RT/Duriod 5880, and Rogers AD600 with different relative permittivities and thicknesses are used in the measurement setup. The results displayed good agreement between model parameters and estimated properties of the presented materials, while the corresponding eigenvectors provided a level of confidence in model parameter values. The results were compared with different reported techniques to showcase the possible use of the presented method in microwave imaging, non-destructive testing, and similar applications.
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Horta Muñoz, Sergio, María del Carmen Serna Moreno, José Miguel González-Domínguez, Pablo Antonio Morales-Rodríguez i Ester Vázquez. "Experimental, Numerical, and Analytical Study on The Effect of Graphene Oxide in The Mechanical Properties of a Solvent-Free Reinforced Epoxy Resin". Polymers 11, nr 12 (16.12.2019): 2115. http://dx.doi.org/10.3390/polym11122115.
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This paper presents a methodology for manufacturing nanocomposites from an epoxy resin reinforced with graphene oxide (GO) nanoparticles. A scalable and sustainable fabrication process, based on a solvent-free method, is proposed with the objective of achieving a high level of GO dispersion, while maintaining matrix performance. The results of three-point bending tests are examined by means of an analytical technique which allows determining the mechanical response of the material under tension and compression from flexural data. As result, an increase of 39% in the compressive elastic modulus of the nanocomposite is found with the addition of 0.3 wt % GO. In parallel, we described how the strain distribution and the failure modes vary with the amount of reinforcement based on digital image correlation (DIC) techniques and scanning electron microscopy (SEM). A novel analytical model, capable of predicting the influence of GO content on the elastic properties of the material, is obtained. Numerical simulations considering the experimental conditions are carried out. the full strain field given by the DIC system is successfully reproduced by means of the finite element method (FEM). While, the experimental failure is explained by the crack growth simulations using the eXtended finite element method (XFEM).
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Sanchez, Martha L., Gil Capote i Julián Carrillo. "Experimental and numerical evaluation of the mechanical behavior of diagonally reinforced plates subjected to the effect of residual thermal stresses". Ingeniería e Investigación 37, nr 3 (1.09.2017): 124–32. http://dx.doi.org/10.15446/ing.investig.v37n3.60633.
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This paper presents an experimental and numerical study of the effect of residual thermal stresses on the mechanical behavior of diagonally reinforced plates. The study focuses on the analysis of carbon/epoxy square plates onto which diagonal reinforcements were glued. These reinforcements were glued using two different methodologies: the first method was to glue the reinforcements at operating temperature (22 °C), while in the second methodology reinforcements were cured in an autoclave at 177 °C. Mechanical behavior assessment was based on the stiffness, free vibration, and buckling tests. For the study of the stiffness of the plates, an optical technique to determine the transversal displacement caused by the presence of a static load was employed. For the vibration tests, the natural frequencies associated with the first four modes of free vibration were determined by using a dynamic signal analyzer. For the linear and non-linear buckling, compression tests on a universal testing machine were performed, determining the displacements produced during the test using the digital image processing method. All experimental results were compared with results obtained from numerical approximations made with commercial software. The results show the effect of residual thermal stresses caused during the manufacturing process on the mechanical performance of diagonally reinforced plates.
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Singh, Mandeep, Sanjeev Kumar, Shervin Zoghi, Yerli Cervantes, Debaki Sarkar, Saquib Ahmed, Shaestagir Chowdhury i Sankha Banerjee. "Fabrication and Characterization of Flexible Three-Phase ZnO-Graphene-Epoxy Electro-Active Thin-Film Nanocomposites: Towards Applications in Wearable Biomedical Devices". Journal of Composites Science 4, nr 3 (4.07.2020): 88. http://dx.doi.org/10.3390/jcs4030088.
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Perovskite oxides have been used as sensors, actuators, transducers, for sound generation and detection, and also in optical instruments and microscopes. Perovskite halides are currently considered as optoelectronic devices such as solar cells, photodetectors, and radiation detection, but there are major issues with stability, interfacial recombination, and electron/hole mobility. The following work looks into the fabrication of non-toxic ZnO-based lead-free alternatives to perovskite oxides for use as secondary sensors or electron transport layers along with perovskite halides for application in stacked biomedical wearable devices. Three-phase, lead-free, Zinc Oxide-Graphene-Epoxy electroactive nanocomposite thin films were fabricated. The volume fraction of the Graphene phase was held constant at 10%, while the volume fraction of the ZnO phase was varied from 10–70%. The dielectric constant, capacitance, impedance, resistance, and conductance of the samples were measured using an impedance analyzer, and the results were compared as a function of volume fraction of ZnO to understand the electron transport performance of these thin films. The impedance and dielectric spectra of the nanocomposites were recorded over a frequency range of 20 Hz to 10 MHz. The microstructural properties and cross-section of the thin films were analyzed using a Scanning Electron Microscope. The high sensitivity and electron transport properties of the composite could be potentially utilized in biomedical devices at low- and high-frequency ranges.
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Pekbey, Yeliz, Goudarz Ghanizadeh Hesar, Hasan Yildiz i Farshid Khosravi Maleki. "Determination of the critical load and energy release rate in mode II delamination using a meshfree method". Science and Engineering of Composite Materials 21, nr 2 (1.03.2014): 223–38. http://dx.doi.org/10.1515/secm-2013-0114.
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AbstractSimulation of fracture by using numerical methods is important to treat geometries that change in time. In this study, both numerical and experimental investigations are presented for the delamination under mode II loading, detailing the derivation of the formulations in numerical simulations of fracture. The simulation of the delamination under mode II loading based on the cohesive segments model was investigated by using a meshfree method. Then, an experimental investigation was used to verify the meshfree method’s results. For tests under mode II loading, three-point end-notched flexure specimens, which are made of carbon/epoxy laminate (AS4/3501-6) which consists of 10 plies in [0]10 and [0/90/0/90/0]s lay-up with delamination inserted in the middle of the laminate, were used for the interlaminar fracture toughness tests. The problem was solved for [0]10, [0/45/-45/90/0]s, [0/90/0/90/0]s, [0/90/0/90/30]s, [0/90/0/90/45]s and [0/90/0/90/60]s laminates with mid-plane delaminations, and the results were verified for different composite materials. The critical fracture force, which can be experimentally measured, was used to calculate the mode II delamination fracture toughness of the carbon/epoxy laminate. In addition, values of the integral for 209 (11×19) and 253 (11×23) background meshes with equivalent interval sizes were compared. For a relatively fine background mesh, the critical load was converged. Results obtained from the meshfree element-free Galerkin method showed very good agreement with experimental data for single-mode delamination under mode II loading. The results presented will help in the implementation of mesh design techniques that protect numerical accuracy while minimizing computational expense.
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Song, Lixin, Qian Zhang, Yongsheng Hao, Yongchao Li, Weihan Chi, Fei Cong, Ying Shi i Li-Zhi Liu. "Effect of Different Comonomers Added to Graft Copolymers on the Properties of PLA/PPC/PLA-g-GMA Blends". Polymers 14, nr 19 (29.09.2022): 4088. http://dx.doi.org/10.3390/polym14194088.
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The melt-free radical grafting of glycidyl methacrylate (GMA) onto poly (lactic acid) (PLA) with styrene (St), α-methylstyrene (AMS), and epoxy resin (EP) as comonomers in a twin-screw extruder was used to prepare PLA-g-GMA graft copolymers. The prepared graft copolymers were then used as compatibilizers to prepare PLA/PPC/PLA-g-GMA blends by melt blending with PLA and polypropylene carbonate (PPC), respectively. The effects of different comonomers in the PLA-g-GMA graft copolymers on the thermal, rheological, optical, and mechanical properties and microstructure of the blends were studied. It was found that the grafting degree of PLA-g-GMA graft copolymers was increased to varying degrees after the introduction of comonomers in the PLA-g-GMA grafting reaction system. When St was used as the comonomer, the grafting degree of the PLA-g-GMA graft copolymer increased most significantly, from 0.8 to 1.6 phr. St as a comonomer also most improved the compatibility between PLA and PPC, and the haze of the blends was reduced while maintaining high transmittance. In addition, the PLA-g-GMA graft copolymer with the introduction of St as a comonomer significantly improved the impact toughness of the blends, while the thermal stability and tensile strength of the blends remained largely unchanged.
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Cespugli, Marco, Simone Lotteria, Luciano Navarini, Valentina Lonzarich, Lorenzo Del Terra, Francesca Vita, Marina Zweyer i in. "Rice Husk as an Inexpensive Renewable Immobilization Carrier for Biocatalysts Employed in the Food, Cosmetic and Polymer Sectors". Catalysts 8, nr 10 (19.10.2018): 471. http://dx.doi.org/10.3390/catal8100471.
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The high cost and environmental impact of fossil-based organic carriers represent a critical bottleneck to their use in large-scale industrial processes. The present study demonstrates the applicability of rice husk as inexpensive renewable carrier for the immobilization of enzymes applicable sectors where the covalent anchorage of the protein is a pre-requisite for preventing protein contamination while assuring the recyclability. Rice husk was oxidized and then functionalized with a di-amino spacer. The morphological characterization shed light on the properties that affect the functionalization processes. Lipase B from Candida antarctica (CaLB) and two commercial asparaginases were immobilized covalently achieving higher immobilization yield than previously reported. All enzymes were immobilized also on commercial epoxy methacrylic resins and the CaLB immobilized on rice husk demonstrated a higher efficiency in the solvent-free polycondensation of dimethylitaconate. CaLB on rice husk appears particularly suitable for applications in highly viscous processes because of the unusual combination of its low density and remarkable mechanical robustness. In the case of the two asparaginases, the biocatalyst immobilized on rice husk performed in aqueous solution at least as efficiently as the enzyme immobilized on methacrylic resins, although the rice husk loaded a lower amount of protein.
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Wu, Xiang-Fa, i Oksana Zholobko. "Experimental Study of the Probabilistic Fatigue Residual Strength of a Carbon Fiber-Reinforced Polymer Matrix Composite". Journal of Composites Science 4, nr 4 (21.11.2020): 173. http://dx.doi.org/10.3390/jcs4040173.
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Degradation of the mechanical properties of fiber-reinforced polymer matrix composites (PMCs) subjected to cyclic loading is crucial to the long-term load-carrying capability of PMC structures in practice. This paper reports the experimental study of fatigue residual tensile strength and its probabilistic distribution in a carbon fiber-reinforced PMC laminate made of unidirectional (UD) carbon-fiber/epoxy prepregs (Hexcel T2G190/F263) with the ply layup [0/±45/90]S after certain cycles of cyclic loading. The residual tensile strengths of the PMC laminates after cyclic loading of 1 (quasistatic), 2000, and 10,000 cycles were determined. Statistical analysis of the experimental data shows that the fatigue residual tensile strength of the PMC laminate follows a two-parameter Weibull distribution model with the credibility ≥ 95%. With increasing fatigue cycles, the mean value of the fatigue residual strength of the PMC specimens decreased while its deviation increased. A free-edge stress model is further adopted to explain the fatigue failure initiation of the composite laminate. The present experimental study is valuable for understanding the fatigue durability of PMC laminates as well as reliable design and performance prediction of composite structures.
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Yang, Marshall Shuai, Jinbao Huang, Hui Zhang, James Joseph Noël, Yolanda Susanne Hedberg, Jian Chen, Ubong Eduok i in. "Study on the Self-Repairing Effect of Nanoclay in Powder Coatings for Corrosion Protection". Coatings 13, nr 7 (7.07.2023): 1220. http://dx.doi.org/10.3390/coatings13071220.
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Powder coatings are a promising, solvent-free alternative to traditional liquid coatings due to the superior corrosion protection they provide. This study investigates the effects of incorporating montmorillonite-based nanoclay additives with different particle sizes into polyester/triglycidyl isocyanurate (polyester/TGIC) powder coatings. The objective is to enhance the corrosion-protective function of the coatings while addressing the limitations of commonly employed epoxy-based coating systems that exhibit inferior UV resistance. The anti-corrosive and surface qualities of the coatings were evaluated via neutral salt spray tests, electrochemical measurements, and surface analytical techniques. Results show that the nanoclay with a larger particle size of 18.38 µm (D50, V) exhibits a better barrier effect at a lower dosage of 4%, while a high dosage leads to severe defects in the coating film. Interestingly, the coating capacitance is found, via electrochemical impedance spectroscopy, to decrease during the immersion test, indicating a self-repairing capability of the nanoclay, arising from its swelling and expansion. Neutral salt spray tests suggest an optimal nanoclay dosage of 2%, with the smaller particle size (8.64 µm, D50, V) nanoclay providing protection for 1.5 times as many salt spray hours as the nanoclay with a larger particle size. Overall, incorporating montmorillonite-based nanoclay additives is suggested to be a cost-effective approach for significantly enhancing the anti-corrosive function of powder coatings, expanding their application to outdoor environments.
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Kadioglu, Ferhat, i Omer Z. Alaboyun. "Damping contribution of the glass reinforced aluminum laminates epoxy to the aluminum based-sandwich structures". Journal of Sandwich Structures & Materials 24, nr 3 (marzec 2022): 1611–28. http://dx.doi.org/10.1177/10996362211053636.
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Despite many potential use of aluminum sandwiches in advanced industries, their poor performance in damping and sound transmission demands new challenges for improvement. This study aims to improve dynamic performance of these sandwiches using hybrid face sheets in the form of Glass Laminate Aluminum Reinforced Epoxy (GLARE). While parameters related to the aluminum honeycomb core were kept constant, the effects of different fiber orientations of the GLARE on the fundamental natural frequency, equivalent flexural modulus, and especially damping values were investigated. The dynamic values of the structures have been measured using a specially designed non-contact vibrating beam test with free-free end conditions. A comparison of the sandwiches with the GLARE and with bare aluminum face sheets has also been made to find out their differences in the dynamic performance. The experimental results were compared to those from a numerical modal analysis via the Altair Hyperworks 2019 Software. The results have shown that the maximum equivalent modulus is obtained from the specimen with the unidirectional (0°) fibers, and the minimum value is from that with the 90° ones. But the opposite is the case if their Specific Damping Capacity values are compared. The values of the specimens with 0°/90° and 0°/45° fibers are on moderate levels. Considerable increments between 54% and 172% are found in the damping values of the specimens with GLAREs, compared to those with the bare aluminum face sheets. The results from the experimental and numerical works have been found in a good agreement.
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Czifrák, Katalin, Csilla Lakatos, Gabriella Szabó, Bence Vadkerti, Lajos Daróczi, Miklós Zsuga i Sándor Kéki. "Bisphenol A Diglycidyl Ether-Primary Amine Cooligomer-poly(ε-caprolactone) Networks: Synthesis and Characterization". Polymers 15, nr 13 (3.07.2023): 2937. http://dx.doi.org/10.3390/polym15132937.
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In this work, the preparation and systematic investigation of cross-linked polyurethane-epoxy (PU-EP) polymer systems are reported. The PU-EP polymers were prepared using a reaction of isocyanate (NCO)-terminated PU-prepolymer with diglycidyl ether of bisphenol A (DGEBA)-amine cooligomer. The oligomerization of DGEBA was carried out by adding furfurylamine (FA) or ethanolamine (EA), resulting in DGEBA-amine cooligomers. For the synthesis of NCO-terminated PU-prepolymer, poly(ε-caprolactone)diol (PCD) (Mn = 2 kg/mol) and 1,6-hexamethylene diisocyanate (HDI) were used. The cross-linking was achieved by adding DGEBA-amine cooligomer to PU-prepolymer, in which the obtained urethane bonds, due to the presence of free hydroxil groups in the activated DGEBA, served as netpoints. During cross-linking, ethanolamine provides an additional free hydroxyl group for the formation of a new urethane bond, while furfurylamine can serve as a thermoreversible coupling element (e.g., Diels–Alder adduct). The PU-EP networks were characterized using attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA) and scanning electron microscopy (SEM). The DMA curves of some PU-EPs (depending on the compositions and the synthetic method) revealed a plateau-like region above the melting temperature (Tm) of PCD, confirming the presence of a cross-linked structure. This property resulted in a shape memory (SM) behavior for these samples, which can be fine-tuned in the presence of furfurylamine through the formation of additional thermoreversible bonds (e.g., Diels–Alder adduct).
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Renaud, Alexis, Victor Pommier, Jérémy Garnier, Simon Frappart, Laure Florimond, Marion Koch, Anne-Marie Grolleau, Céline Puente-Lelièvre i Touzain Sebastien. "Aggressiveness of Different Ageing Conditions for Three Thick Marine Epoxy Systems". Corrosion and Materials Degradation 2, nr 4 (3.12.2021): 721–42. http://dx.doi.org/10.3390/cmd2040039.
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Three different coated steel systems were aged in natural or artificial seawater, in neutral salt spray (NSS), and using alternate immersion tests in order to evaluate the aggressiveness of the different ageing conditions. Commercial epoxy coatings were applied onto steel (S355NL), hot-galvanized steel (HDG), and Zn-Al15 thermal spraying coated steel. The defect-free systems were immersed in artificial seawater at 35 °C for 1085 days and in natural seawater for 1200 days and were characterized by electrochemical impedance spectroscopy (EIS). Panels with artificial defects were immersed for 180 days in artificial seawater and, regarding adhesion, were evaluated according to ISO 16276-2. In parallel, the three coated systems were submitted to cyclic neutral salt spray (NSS) for 1440 h: defect-free panels were regularly evaluated by EIS, while the degree or corrosion was measured onto panels with artificial defect. After NSS, defect-free panels were immersed in artificial seawater at 35 °C for further EIS investigations. Finally, alternate immersion tests were performed for 860 days for the three defect-free coated systems and for 84 days for panels with a defect. The results showed that, for defect-free panels, immersions in natural or artificial seawater and NSS did not allowed us to distinguish the three different systems that show excellent anticorrosion properties. However, during the alternate immersion test, the organic coating system applied onto HDG presented blisters, showing a greater sensitivity to this test than the two other systems. For panels with a defect, NSS allowed to age the coatings more rapidly than monotone conditions, and the coating system applied onto steel presented the highest degree of corrosion. Meanwhile, the coating systems applied onto HDG and the thermal spray metallic coating showed similar behavior. During the alternate immersion test, the three coated systems with a defect showed clearly different behaviors, therefore it was possible to rank the three systems. Finally, it appeared that the alternate immersion test was the most aggressive condition. It was then proposed that a realistic thermal cycling and an artificial defect are needed when performing ageing tests of thick marine organic coating systems in order to properly rank/evaluate the different systems.
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Moise, Călin, Lidar Rachmani, Geanina Mihai, Oana Lazar, Marius Enăchescu i Naum Naveh. "Pulsed Laser Deposition of SWCNTs on Carbon Fibres: Effect of Deposition Temperature". Polymers 13, nr 7 (2.04.2021): 1138. http://dx.doi.org/10.3390/polym13071138.
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Single wall carbon nanotubes (SWCNTs) were grown on either sized or desized carbon fabric in a self-designed reactor by Pulsed Laser Deposition (PLD). The uniqueness of the PLD system lies, among other things, in the ability to keep the substrate at a low temperature, compared to the 1100 °C needed for the SWCNTs synthesis, thus, rendering it undamaged. Samples were placed at different positions on a cold finger (CF), where a temperature gradient develops, in the range 25–565 °C. The chemical composition and morphology of desized and surface treatments, as well as SWCNTs grown on carbon fibres, were verified by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-Ray Spectroscopy (EDX), while the quality of SWCNTs was proven by confocal micro-Raman Spectroscopy and High-Resolution Scanning Transmission Electron Microscopy (HR-STEM). Fibres covered with SWCNTs by PLD were characterized using contact angle and the surface free energy was calculated. A micro-droplet pull-out test was used to evaluate the effect of SWCNTs over interfacial properties of a carbon-epoxy composite. A 20% increase in interfacial shear strength (IFSS) was observed by deposition at 290 °C, compared to the commercial carbon fibre sizing. The carbon fibres kept their tensile properties due to the low deposition temperatures.
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Li, Xinxin, i Jinku Xu. "A Simple Synthesis of Higher Refractive Index Polymeric Nanocomposite Containing the Pendant ZnS Nanocrystals Capping Different Amount of Mercaptoethanol". Journal of Nanomaterials 2020 (11.08.2020): 1–13. http://dx.doi.org/10.1155/2020/7350367.
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In this paper, three kinds of ZnS NPs capping different amount of mercaptoethanol (ME) were synthesized, and the effect of capping amount on ZnS NPs was studied, indicating that the capping amount of ME on ZnS surface decreases, while ZnS size increases as the decrease of added capping agent in synthesis process, and ZnS NP capping middle amount of ME (~27.7 wt%) shows a highest apparent refractive index (RI) value. ZnS NPs were composited into polymeric matrices by a simple “one-step” thermocuring method characterized by adding a small amount of functional monomer of glycidyl methacrylate (GMA) and solvent of N,N-dimethylformamide (DMF) The reaction mechanism, studied by 1H NMR spectra, indicates that the epoxy of GMA monomer can be easily opened and chemically grafted on ME-capped ZnS surface under the catalysis of DMF, and then copolymerized with other monomer. By the route, ZnS NPs can be composited into pure poly(N,N-dimethylacrylamide)-type (DMA-type), DMA-type copolymer, and DMA-free matrices to fabricate transparent films, and its RI value can be improved by either optimizing capping amount on ZnS surface or increasing ZnS content in the nanocomposites. The RI value of resulting dried nanocomposites can be improved to 1.764 by compositing 80 wt% ZnS capping middle amount of ME.