1,720,984 research outputs found
Toughening of Epoxy Resin via Silane Terminated Urethane Including Pre-Hydrolyzed Tetraethoxysilane
No full textIn this Study, firstly; Silane terminated urethane was synthesized from poly(hexamethylene carbonate) diol and 3-isocyanatopropyl trimethoXysilane. Prepared solutions of inorganic part (silane terminated urethane + pre-hYdrolyzed tetraethoxysildne) were Mixed with epoxy-hardenet mixture to obtain hybrid solutions. Various hybrid Solutions were prepareclnsing different epoxy/inorganic part solution:compositions. Furthermore, ther'effect of silane terminated urethane on the mechanical and morphological properties of epoxy was investigated. The structure and pioperties of the composites are characterized using a scanning:electron Microscopy. Epoxy/silane, terminated I urethane hybrid materials were Subjected to examinations to obtain their tensile strength, three point bending properties, hardness, izod impact strength. Incorporation of silane terminated urethane into the epoxy resin greatly Modified the impact behavior of hybrids
Effect of hornbeam sawdust size on the mechanical properties of polyethylene composites
No full textComposite materials obtained with natural and sustainable fibers can be used successfully in many areas on their own. In recent years, high-strength fibers such as hemp, sisal, linen, jute, wood sawdust and bamboo are more preferred in composite materials. In this study, the effect of the hornbeam sawdust size on the mechanical properties of polyethylene was investigated. For this purpose, different sizes of hornbeam sawdust were added to polyethylene. Hornbeam sawdust was added to the polyethylene matrix in four different weight ratios (5, 10, 15 and 20%) by way of the extrusion method. Test samples were prepared out of those mixtures by injection-molding. Tensile, Izod impact and hardness tests were performed on the samples. The elastic modulus increased with increasing hornbeam sawdust content. However, elongation at break and Izod impact strength values decreased. Modulus of elasticity, tensile strength, elongation at break and Izod impact strength values decreased with increasing hornbeam sawdust size. The morphology of composite samples was examined by scanning electron microscopy. The results show that the hornbeam sawdust can be used as a filler in polymer-based composites
Investigation of Properties of Fluorine Containing Hybrid Coatings Intended for Use in Printing
No full textThe effect of chestnut wood flour size on the mechanical properties of vinyl ester composites
No full textGreen composites are a special class of composites in which at least one of the components is obtained from natural resources. They are an alternative to traditional composites because of their useful properties such as biodegradability, low cost, easy processability, sound insulation and recycling. Green composites, which emerge as environmentally friendly polymeric composite materials, offer techno-economic advantages in commercial and engineering applications and are among the widely dealt subjects due to the very high demand from the global market. The aim of this study is to investigate the effect of chestnut wood flour size on the mechanical properties of chestnut-wood-flour-filled vinyl ester composites. With this aim, composite specimens were produced by using vinyl ester polymer as the matrix material and chestnut wood flour in three different sizes (0-150, 150-315 and 315-400 mm) as the natural filler. In each size combination, four different matrix/filler ratios (5, 10, 15 and 20% by weight) were adopted. These mixtures were then poured into Teflon moulds to produce the test specimens. Izod impact, three-point bending, hardness and tensile strength tests were performed on the composite specimens. In addition, morphological investigations were performed on the fractured surfaces of the specimens by using scanning electron microscopy. It is concluded that composites with a small-sized chestnut wood flour as the filler have superior properties for composite applications
Monte Carlo simulations study on gamma ray-neutron shielding characteristics for vinyl ester composites
No full textThe current study aims to report the gamma ray-neutron attenuation parameters of eight types of vinyl ester pumice (V-P) composites for wide energy ranges of 511-2140 keV via MCNPX and FLUKA codes. The radiation shielding properties of these composites were presented graphically and are discussed in detail in this study. From the obtained results, it can be concluded that the MCNPX and FLUKA outcomes are in agreement with each other, and also the FLUKA code can be used as an alternative technique to determine the attenuation features of vinyl ester composites. Besides, the linear attenuation coefficient and total macroscopic cross sections' ( n-ary sumation (t)) dependencies on the density and also mass attenuation coefficient were found for all selected samples. To sum up, findings show that composite coded as V-P50 can be a good competitive candidate in terms of gamma rays and neutron shielding
The preparation of UV-cured superhydrophobic cotton fabric surfaces by electrospinning method
No full textElectrospinning was used for the coating of the polyurethane/silica hybrid solutions on the cotton fabric surface. An ultraviolet curing process was performed on the collector by an ultraviolet lamp positioned inside the electrospinning cabin. In order to investigate the effect of fluorinated, silane-functionalized urethane (inorganic part) content on the water-repellency; five different fluorinated concentrations (10%, 20%, 30%, 40%, and 50% by weight) were used. The disappearance of isocyanate peaks during the silane-functionalized urethane synthesis was observed by Fourier transform infrared spectroscopy. Surface morphology and elemental analysis of the coated cotton fabric surfaces was investigated by scanning electron microscopy and energy dispersive spectroscopy analysis respectively. Water-repellency was evaluated by contact angle measurements. A sample that contained 50% inorganic part showed a contact angle of 154.5 degrees. Samples were thermally characterized by differential scanning calorimetry. Glass transition temperature of the synthesized hybrid polymer increased with increasing inorganic part ratio. Additionally, abrasion resistance and crease recovery angle tests were performed to evaluate the effect of fluorinated part percentage on the mechanical and comfort properties of fabrics
Preparation of fluorine containing hybrid coatings: investigation of coating performance onto ABS and PMMA substrates
No full textUV-curable fluorinated organic-inorganic hybrid coatings were prepared by the sol-gel technique. Perfluorinated urethane modified alkoxysilane was synthesized by the reaction between perfluoro alcohol and 3-isocyanatopropyltrimethoxysilane. The prepared formulations were applied onto poly(methyl methacrylate) (PMMA) and acrylonitrile butadiene styrene (ABS) panels and polymerized by UV-curing. The properties of the hybrid coatings such as hardness, chemical resistance, thermal stability, surface morphology, double bond conversion, and also contact angle measurements were investigated. Contact angle measurements have shown that the addition of fluorinated silane precursor to the hybrid system improved the water repellency and increased the contact angle from 65 degrees to 106 degrees. Copyright (C) 2009 John Wiley & Sons, Ltd
3D printing of chitosan/ poly(vinyl alcohol) hydrogel containing synthesized hydroxyapatite scaffolds for hard-tissue engineering
No full textIn recent years, 3D printed scaffolds becoming a widespread tool, which supports the repair mechanism of natural tissues. In order to support this knowledge, we used 3D printing methods to fabricated Chitosan (CH)/poly(vinyl alcohol)(PVA)-based scaffolds contains with a various ratio of hydroxyapatite (HA) (2.5, 5, 10, and 15 wt%). These composited scaffolds were further characterized for their chemical, morphological, mechanical, and biocompatibility properties. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), swelling test, and compressive strength test were performed to reveal structural, mechanical and chemical characteristics of scaffolds. Among others, 15 wt% HA contained group demonstrated significantly superior and beneficial features in printing quality. Also, the results reveal that scaffolds have similar elastic modulus to natural bone. Bone morphogenetic protein-2 (BMP-2) protein was added to the most successful mechanically produced sample. As a result, it was shown that Chitosan/PVA/HA (15 wt%) with BMP-2 tissue scaffold could form a three-dimensional natural extracellular scaffold suitable for human mesenchymal stem cells. Altogether, these results show that hydroxyapatite added scaffolds produced may be a promising approach for bone tissue engineering applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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