1,721,001 research outputs found
Mechanical Properties of Glass Bead- and Wollastonite-Filled Isotactic-Polypropylene Composites Modified With Thermoplastic Elastomers
No full textMechanical properties of the isotactic-polypropylene/glass bead (iPP/GB) and iPP/wollastonite (iPP/W) composites modified with thermoplastic elastomers, the poly(styrene-b-ethylene-co-butylene-b-styrene) copolymer (SEBS) and corresponding block copolymer grafted with maleic anhydride (SEBS-g-MA), were investigated. An increase in toughness of iPP with the elastomers was associated with a decrease in rigidity and strength. Mechanical performance of iPP increased more with acicular W than with spherical GB due to reinforcing effect of W. Comparing the (iPP/GB)/SEBS and (iPP/W)/SEBS composites having the separate microstructure, strength and toughness values of the iPP/GB and iPP/W composites increased more with SEBS-g-MA at the expense of rigidity due to the core-shell microstructure with strong interfacial adhesion. Moreover, the iPP/W composite exhibited superior mechanical performance with 2.5 and 5 vol% of SEBS-g-MA because of a positive synergy between the core-shell microstructure and reinforcing effect of acicular W. The extended models revealed that the elastomer and filler particles in the (iPP/GB)/SEBS and (iPP/W)/ SEBS composites acted individually due to the separate microstructure. However, the rigid GB and W particles encapsulated with the thick elastomer interlayer (R(0)/R(1) = 0.91) in the (iPP/GB)/SEBS-g-MA and (iPP/W)/ SEBS-g-MA composites acted like neither big elastomer particles nor like individual rigid particles, inferring more complicated failure mechanisms in the core-shell composites. POLYM. COMPOS., 31:1285-1308, 2010. (C) 2010 Society of Plastics Engineer
Examining the Mechanical and Thermomechanical Properties of Polymethylmethacrylate Composites Reinforced with Nettle Fibres
No full textThe aim of this study was to determine the mechanical and thermomechanical properties of nettle fibre-reinforced polymethylmethacrylate composites. The polymethylmethacrylate composites reinforced with nettle fibres were manufactured using nettle fibres obtained using the natural methods. The nettle fibre contents were 0, 2.5, 5, 7.5, and 10 V-f %. The composites so formed were characterized in terms of their mechanical and thermomechanical properties. The mechanical properties of nettle-reinforced composites were characterized in terms of bending stress, bending modulus, impact strength, and fracture toughness tests, whilst their behaviour was determined by heat deviation temperature and Vicat softening temperature. The micro-mechanisms underlying the toughening and fracture processes were observed in the light of studies of the microstructure of fractures. From the mechanical properties of composites reinforced with 10% nettle fibres, an increase of 75% in bending stress, 40% in impact strength, and 106% in fracture toughness was recorded. The findings show that nettle fibres can be used as an important reinforcement material for environmentally friendly composite applications
Microstructural Characteristics of Glass Bead- and Wollastonite-Filled Isotactic-Polypropylene Composites Modified With Thermoplastic Elastomers
No full textMicrostructural characteristics of isotactic-polypropylene/glass bead (iPP/GB) and iPP/wollastonite (iPP/W) composites modified with thermoplastic elastomers, poly(styrene-b-ethylene-co-butylene-b-styrene) copolymer (SEBS) and corresponding block copolymer grafted with maleic anhydride (SEBS-g-MA), were investigated. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and dynamic mechanical analyses (DMA) showed that the iPP/SEBS and iPP/SEBS-g-MA blends were partially compatible two-phase systems. Well-dispersed spherical GB and acicular W particles without evidence of interfacial adhesion were observed in the iPP/GB and iPP/W binary composites respectively. Contrary to the blends, melt flow rates of the iPP/GB and PP/W composites decreased more with SEBS-g-MA than with SEBS because of enhanced interfacial adhesion with SEBS-g-MA elastomer. The SEM analyses showed that the ternary composites containing SEBS exhibited separate dispersion of the rigid filler and elastomer particles (i.e., separate microstructure). However, SEBS-g-MA elastomer not only encapsulated the spherical GB and acicular W particles completely with strong interfacial adhesion (i.e., core-shell microstructure) but also dispersed separately throughout iPP matrix. In accordance with the SEM observations, the DSC and DMA revealed quantitatively that the rigid filler and SEBS particles in iPP matrix acted individually, whereas the rigid filler particles in the ternary composites containing SEBS-g-MA acted like elastomer particles because of the thick elastomer interlayer around the filler particles. The Fourier transform infrared analyses revealed an esterification reaction inducing the strong interfacial adhesion between the SEBS-g-MA phase and the filler particles. POLYM. COMPOS., 31:1265-1284, 2010. (C) 2009 Society of Plastics Engineer
The 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
Effects of welding procedures on mechanical and morphological properties of hot gas butt welded PE, PP, and PVC sheets
No full textMechanical and morphological properties of hot gas butt welds on polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) sheets for four different procedures, which are single and double V-welds with and without a welding shoe, were investigated. Besides, weldabilities of base materials were evaluated by rheological measurements. These revealed that weldabilities of PE and PP sheets were better than that of PVC. Welding energy (E-w), which is transferred onto weld surfaces, was calculated to evaluate weld quality. The results of tensile, impact, and bending tests indicated that the weld strengths of PVC sheets were lower than those of PE and PP sheets. When the welding shoe was used, weld strength increased significantly for each material because of the presence of sufficient welding pressure and the effective heating on surfaces. The best results were attained for the double V-welds with the welding shoe. Morphology of welded regions was evaluated by polarized light, stereo, and scanning electron microscopy. Polarized light microscopy studies indicated that the heat-affected zone (HAZ) consisted of welding rod core, molten zone, and deformed spherulitic zone, and the welding interface was indistinguishable from the base material when the welding pressure was enough
Synthesis and Optical Properties of Novel Red-Emitting PbNb2O6: Eu3+ Phosphors
Full text linkUndoped and PbNb2O6:Eu3+ (1.0 aecurrency sign x aecurrency sign 6.0 mol%) phosphors were synthesized at 1100 A degrees C for 3.5 h by the conventional solid state reaction method. Synthesized PbNb2O6:Eu3+ phosphors were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and Photoluminescence (PL) analyses. The PL spectra showed series of excitation peaks between 350 and 430 nm due to the 4f-4f transitions of Eu3+. For 395.0 nm excitation, emission spectra of Eu3+ doped samples were observed at 591 nm (orange) and 614 nm (red) due to the D-5(0) -> F-7(1) transitions and D-5(0) -> F-7(2) transitions, respectively. PL analysis results also showed that the emission intensity increased by increasing Eu3+ ion content. No concentration quenching effect was observed. The CIE chromaticity color coordinates (x,y) of the PbNb2O6:Eu3+ phosphors were found to be in the red region of the chromaticity diagram
Dimensional analyses and surface quality of the laser cutting process for engineering plastics
No full textIn this study, the effect of the CO2 laser cutting process parameters (gas pressure, cutting speed, and laser power) on the dimensional accuracy and measured surface roughness of engineering plastic (PTFE and POM) materials was investigated. Cutting surface profile of specimens was examined by using an optical microscope. The surface quality of specimens was examined by measuring surface roughness and form error. Analysis of variance (ANOVA) and regression analyses are employed to assess the effect of the process parameters on the dimensional accuracy
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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