bluuebunny/crossref_metadata_2025_split huggingface dataset:
‘Elasticisation’ and plasticisation of PVC with ethylene‐vinyl acetate copolymers
Authors: Hardt D. 
Published: March 2007

AbstractCopolymers of ethylene and vinyl acetate (E‐VA) of a certain composition can be used for the improvement of impact properties (elasticisation) of PVC as well as under certain conditions (grafting) for the preparation of flexible PVC (plasticisation). Products of interesting properties are prepared by blending E‐VA (up to ∼ 12%) with PVC or more advantageously by grafting vinyl chloride on special E‐VA types. Graft copolymerisation by the suspension method allows the synthesis of E‐VA/PVC systems in all ratios (up to 80% E‐VA); these polymers are compatible over the whole range in contrast to the blends.Studies on the grafting efficiency of some monomers show that vinyl chloride can be grafted readily on E‐VA.The grafting process is performed on a technical scale to give PVC types with E‐VA contents up to 50%. Products with 6–8% E‐VA should be classified as impact‐modified suspension PVC. Flexible types (40–60% E‐VA) have properties of flexible PVC with the plasticiser chemically incorporated, but may also be blended with unmodified PVC to give impact‐improved formulations.The properties of the elasticised PVC (8% E‐VA) mainly depend on the vinyl acetate (V‐OAc) content of the E‐VA and its molecular weight. Levapren® 450 P (45% V‐OAc; mol. wt. ∼ 100,000), a solution process copolymer, has good elasticising efficiency in blends and graft copolymers with PVC.PVC/E‐VA products may be processed with or without addition of uncombined PVC into rigid or flexible PVC by the usual methods of PVC technology, e.g. extrusion, injection moulding, blow‐moulding and calendering.Competitive modifiers, such as acrylonitrile‐butadiene‐styrene copolymers, methacrylate‐butadiene‐styrene copolymers, acrylates or chlorinated polyethylene, are compared with E‐VA. Levapren® 450 P shows high efficiency as an impact modifier even in low concentration, giving good processability and ageing behaviour. Glass‐clear high‐impact PVC cannot be obtained by E‐VA modification.Some electron microscopy studies to characterise the distribution of E‐VA in the resin phase (PVC) are described; these showed the presence of a two‐phase system.
Vinyl acetate‐ethylene copolymer dispersions
Authors: Reynolds G. E. J. 
Published: March 2007

AbstractThe function of ethylene as a plasticising comonomer for vinyl acetate is reviewed from the historical standpoint and in relation to alternative methods of plasticisation. Both chemical and physical effects are considered. Emulsion polymerisation and the use of aqueous dispersions are covered in some detail, and methods of polymer characterisation are summarised, with particular reference to i.r. and n.m.r. spectroscopy.
Dynamic wetting of glass fibre and polymer fibre
Authors: Inverarity G. 
Published: March 2007

AbstractTo achieve high strength and chemical resistance in glass‐reinforced plastics, it has been found essential to have a good bond between matrix and reinforcement. To obtain this bond it is necessary that good wetting of reinforcement by matrix must occur at some stage in the production cycle.Modern process developments have reduced the time during which wetting can occur to a few seconds in continuous sheeting manufacture. The wetting stage of this process has been investigated by the observation of dynamic contact angles. The rate of wetting has been found to be controlled by liquid flow and not surface tension at high processing speeds. Breakdown of this flow and intermittent wetting have been observed directly.When low energy surfaces are wetted by water, a different limiting factor is found. It is observed that a maximum dynamic contact angle is reached at relatively low wetting rates. It is suggested that these maximum angles offer a new means of assessing Zisman's ‘critical surface tension’ (γc) and by an extension of the technique may enable values of spreading pressure (π) to be measured.
Molecular characterisation by electric field light‐scattering
Authors: Jennings B. R. 
Published: March 2007

AbstractExamination of the intensity of the light scattered from a solution of randomly distributed and oriented molecules, whose major dimensions are of the order of the wavelength of visible light, leads to information about the molecular size. When subjected to electric fields, the molecules become orientated and aligned, thereby changing the polar intensity scattering diagram. Measurements of the intensity changes lead to a host of additional molecular parameters. An outline of the method is given, with particular emphasis being laid on the basic physical principles. Details of the apparatus, the handling of the experimental data and the type of molecular information that can be obtained using direct, alternating and pulsed electric fields are given. Measurements of the equivalent changes in scattered intensity due to d.c. using a.c. fields are probably the most useful as they lead to information on the dipole moments, relaxation time, flexibility and polydispersity of the sample and yet involve little modification to commercial scattering photometers.
Dispersibility of carbon black by polyvinyl alcohol solutions
Authors: Johnson G. A. , Lewis K. E. 
Published: March 2007

AbstractThe dispersibility of carbon black by eight types of polyvinyl alcohol solution has been studied which differed in their degree of hydrolysis (i.e. amount of free acetate groups) and molecular weight. The degree of hydrolysis varied from 80 to 100% and the molecular weight (viscosity average) from 6000 to 40,000. Adsorption isotherms of the polyvinyl alcohol on to the carbon black and contact angles of water on carbon black on to which polyvinyl alcohol had been previously adsorbed were measured. These results are related to the concentration at which dispersion occurs. It is shown that dispersion occurs when the contact angle falls below 90° but that this does not correspond to monolayer coverage of the polyvinyl alcohol on the carbon black. In fact, dispersion occurs at very low levels of adsorption, suggesting that only a low surface coverage is necessary to produce a hydrophilic surface.
Initiator complexes derived from dichlorobiscyclopentadienyl titanium and alkyl aluminium compounds: I. The reduction reaction
Authors: Amass A. J. , Hay J. N. , Robb J. C. 
Published: March 2007

AbstractA general mechanism of the reduction of dichloro‐biscyclopentadienyl titanium with triethyl aluminium has been derived from a study of the reaction at −70° in toluene and n‐heptane solutions. The reaction products were found to depend on the Al:Ti molar ratio. Each product was examined as active initiators for the homopolymerisation of styrene at 60°.
Initiator complexes derived from dichlorobiscyclopentadienyl titanium and alkyl aluminium compounds: III. copolymerisation
Authors: Amass A. J. , Hay J. N. , Robb J. C. 
Published: March 2007

AbstractCopolymerisation studies have been made with styrene and 4‐methylpentene‐1 using the soluble initiator system dichloro‐biscyclopentadienyl titanium‐triethyl aluminium. Results confirm that a free radical mechanism rather than a co‐ordinated anionic mechanism is operative.
Initiator complexes derived from dichlorobiscyclopentadienyl titanium and alkyl aluminium compounds: IV. Di‐isobutyl aluminium hydride
Authors: Alexander I. J. , Hay J. N. , Robb J. C. 
Published: March 2007

AbstractComplexes produced in the reaction of dichloro‐biscyclopentadienyl titanium and di‐isobutyl aluminium hydride (DBAH) have been studied as initiators for the polymerisation of styrene and characterised spectroscopically. In general the complexes do not initiate and the observed dilatometric contractions can be attributed to a reaction between styrene and DBAH. The limited amount of polymerisation observed can be associated with a radical process involved in the reduction of Ti(IV) to Ti(III).
Studies on cation‐exchange resins: I. Chelating properties of cation exchangers prepared from cold extracted commercial cashewnutshell liquid
Authors: Dasare B. D. , Krishnaswamy N. 
Published: March 2007

AbstractFour weakly acidic cation exchangers have been prepared, one by the polycondensation of cold extracted commercial cashewnutshell liquid (C‐CNSL) with formaldehyde and the other three by the co‐condensation of C‐CNSL with formaldehyde and each of the compounds gallic acid, anthranilic acid and 2‐mercapto‐benzothiazole. The resins have been investigated for the selective uptake of cations from external solutions of different pH. The resin prepared by polycondensation of C‐CNSL and the one prepared by its co‐condensation with gallic acid showed comparatively specific absorption of Fe2+ ions.
Emulsion Polymerisation of Styrene and Vinyl Acetate
Authors: Breitenbach J. W. , Kuchner K. , Fritze H. , Tarnowiecki H. 
Published: March 2007

AbstractKinetic data on the emulsion polymerisation of styrene are discussed in the light of the Smith‐Ewart theory as modified by Gardon. It is shown that at least in the beginning of the reaction serious discrepances exist between experimental results and the theoretical concept. An electrolytic effect in cationic emulsifier systems was found. Emulsion polymerisation of vinyl acetate was investigated and the mechanism is discussed. The polymerisation of vinyl acetate in aqueous solution without added emulsifier begins as a true solution polymerisation but very soon changes to a suspension polymerisation. The latex particles formed are an order of magnitude larger than those obtained in the emulsion polymerisation and have a very narrow size distribution. There seems to be a very short period of particle formation in this system.
Continuous emulsion polymerisation of styrene and methyl acrylate
Authors: Gerrens H. , Kuchner K. 
Published: March 2007

AbstractAn investigation of continuous emulsion polymerisation kinetics was carried out using a series of three continuous stirred tank reactors (CSTR), and styrene and methyl acrylate as types of monomer with different solubilities in water.Steady‐state conversion fluctuations reported in the literature could be suppressed by holding the feed rates constant.The results obtained are only partly in agreement with the theory proposed by Gershberg & Longfield, who combined the basic assumptions of the Smith‐Ewart theory with steady‐state CSTR kinetics.An explanation for the deviations from this theory is therefore suggested which takes into account the tendency of relatively water‐soluble monomers to form particles from the homogeneous solution and to undergo so‐called interparticle termination as a result of migration of radicals between the latex particles.
Relationship between specific surface area and pore dimension of high porosity nanoporous silicon – Model and experiment
Authors: du Plessis Monuko 
Published: March 2007

AbstractThe structural properties of high porosity nanoporous silicon were researched with the manufacture of integrated nano‐explosive devices in mind. A three‐dimensional nanoporous layer structural model, consisting of cylindrical crystallites, is proposed. Model parameters are derived from gravimetric techniques and the electrochemical etching of high porosity nanoporous silicon layers. A gravimetric experimental technique is described whereby the pore dimensions and specific surface area of nanoporous regions can be determined. An inverse relationship between pore size and specific surface area is found, with a constant specific surface area times pore diameter product. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication and characterization of orientated grown AlN films sputtered at room temperature
Authors: Gao X. D. , Jiang E. Y. , Liu H. H. , Li G. K. , Mi W. B. , Li Z. Q. , Wu P. , Bai H. L. 
Published: March 2007

AbstractAlN films have been fabricated using a dc magnetron sputtering system under different N2 partial pressures, PN, without substrate heating. X‐ray diffraction revealed that the AlN(002) peak intensity increases first with increasing PN (10–40%) and then drops when PN is increased to 50%. Optical transmission studies derived the refractive index of 1.84–1.91 and the optical band gap of 5.83–5.91 eV. Strong absorption caused by the oxygen impurities and nitrogen vacancies was observed in the transmission spectrum of the sample fabricated under PN of 10%. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparation, characterization and luminescence property of YPO4:Eu nanocrystals
Authors: Lai Hua , Yang Hua , Tao Chunyan , Yang Xuwei 
Published: March 2007

AbstractCo‐precipitation reaction soft chemistry method was employed to prepare fine YPO4:Eu3+ phosphor particles calcined at different temperature. Adjusting appropriate pH and introducing lithium may greatly affect the particle size of the sample and further affect the luminescence intensity. The as‐prepared samples were characterized by X‐ray diffraction (XRD), transmission electron micrograph (TEM) and photoluminescence (PL) spectroscopy. The XRD patterns of YPO4:Eu3+ have only peaks of tetragonal xenotime and the sizes of particles range from 8 to 12 nm without Li2CO3 flux. The addition of Li2CO3 flux to precursor leads to a morphological modification for both the shape and size of the final phosphor, further affect the luminescence intensity. From the fluorescence spectra the emission transition 5D0 → 7F1 is more prominent than the normal red emission transition (5D0 → 7F2). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupling mechanisms for split ring resonators: Theory and experiment
Authors: Hesmer Frank , Tatartschuk Eugen , Zhuromskyy Oleksandr , Radkovskaya Anna A. , Shamonin Mikahil , Hao Tong , Stevens Chris J. , Faulkner Grahame , Edwards David J. , Shamonina Ekaterina 
Published: March 2007

AbstractWe study experimentally and theoretically coupling mechanisms between metamaterial elements of the split ring resonator (SRR) type. We show that, depending on the orientation of the elements relative to each other, the coupling may be either of magnetic or electric type or a combination of both. Experimental results on SRRs with resonances around 1.7–1.9 GHz agree quantitatively with results of simulations (CST Microwave Studio). Further simulations provide analysis for a variety of SRRs both in the GHz and in the 20 THz frequency regions. The variety of coupling mechanisms can be employed in designing near field manipulating devices based on propagation of slow waves. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic response of split ring resonators at terahertz frequencies
Authors: Soukoulis Costas M. , Koschny Thomas , Zhou Jiangfeng , Kafesaki Maria , Economou Eleftherios N. 
Published: March 2007

AbstractWe investigate numerically the electric and the magnetic response of the split‐ring resonators (SRRs) for different electromagnetic (EM) field polarization and propagation directions. We have studied the current density J of circular and rectangular SRRs at THz frequencies. At low frequencies, J is confined to the edges of the SRRs, while at high frequencies J is all over the width of the wire. The diamagnetic response of the SRRs is also examined. Finally, the role of losses and the magnetic resonance frequency are studied as the size of the SRRs becomes less than 100 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Planar bilayer metamaterial with left‐handed transmission and negative refraction at microwave frequencies
Authors: Özgür Çakmak Atilla , Guven Kaan , Özbay Ekmel 
Published: March 2007

AbstractA planar composite metamaterial consisting of bilayers of metal cutwire pairs and long wire pairs which are separated by a thin dielectric layer is designed and fabricated for microwave frequencies. The simulated and experimentally measured transmission spectra of the metamaterial and its individual components (cutwire‐only and wire‐only) indicates that the metamaterial exhibits a transmission band within the common stop bands of its components, and thus acts as a medium with negative index of refraction. The existence of n < 0 is further supported by a refraction experiment. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radiation properties of a split ring resonator and monopole composite
Authors: Alici Kamil Boratay , Özbay Ekmel 
Published: March 2007

AbstractWe studied the far field radiation properties of a new resonator antenna composed of split ring resonators (SRRs) and a monopole. It is shown that the antenna size at the operation frequency (3.52 GHz) is approximately one tenth of the free space wavelength (λ/10). Moreover, increasing the number of SRRs yields steerability properties. These achievements provide a way to create rather small steerable resonant antennas. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transmission, refraction, and focusing properties of labyrinth based left‐handed metamaterials
Authors: Özbay Ekmel , Bulu Irfan , Caglayan Humeyra 
Published: March 2007

AbstractIn this present article, we studied the transmission, refraction and focusing properties of one, two and three dimensional labyrinth based left‐handed metamaterials. We demonstrated that the proper periodic arrangement of labyrinth structures and wires results in left‐handed transmission. By using a two dimensional labyrinth based left‐handed slab, it is shown that it is possible to image the field emitted from source in sub‐wavelength detail. Moreover, we demonstrated the focusing and negative refraction of electromagnetic waves by a three dimensional labyrinth based left‐handed slab. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Selective lasing in multimode periodic and non‐periodic nanopillar waveguides
Authors: Zhukovsky Sergei V. , Chigrin Dmitry N. , Lavrinenko Andrei V. , Kroha Johann 
Published: March 2007

AbstractThe lasing action in coupled multiple‐row periodic and fractal Cantor‐like nanopillar waveguides has been numerically investigated. It had been shown earlier [D. N. Chigrin et al., Opt. Express 12, 617 (2004)] that such a system exhibits band splitting with distinct, straightforward and controllable supermode formation. In this paper we demonstrate that selective lasing into each of the supermodes is possible. The structure acts as a microlaser with selectable wavelength. Mode selection is achieved by means of coaxial injection seeding with a Gaussian signal with different transverse envelope. The proposed concept of switchable lasing is viewed as an alternative to conventional laser tuning by means of external cavity control. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dual composite right/left‐handed (D‐CRLH) leaky‐wave antenna with low beam squinting and tunable group velocity
Authors: Caloz Christophe , Abielmona Samer , Van Nguyen Hoang , Rennings Andre 
Published: March 2007

AbstractThe propagation and radiation properties of dual composite right/left‐handed (D‐CRLH) transmission line metamaterials are presented, and validated experimentally with a 1D microstrip prototype. In its fast‐wave regime, this structure operates as a leaky‐wave antenna capable of backfire‐to‐endfire radiation scanning with beam squinting smaller than that of conventional CRLH (C‐CRLH) antennas. It is shown that this D‐CRLH beam squinting can be further reduced by increasing the group velocity but that this can occur, close (and possibly beyond) to luminal velocities, only at the expense of losses produced by parasitic effects, a fundamental limitation which is demonstrated via the Bloch impedance concept. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radio frequency (RF) metamaterials
Authors: Wiltshire M. C. K. 
Published: March 2007

AbstractBy studying metamaterials at low frequency, where wavelengths are much larger than the unit cell, the requirements of homogenization and the effective medium approximation can be easily met. The Swiss Roll medium is well‐suited to the RF frequency range, and here we review its behaviour, both as a one‐dimensional system where endoscope behaviour and magnetic “plasmons” are observed, and as a two dimensional structure which has been used to demonstrate sub‐wavelength (λ /64 resolution) imaging. In both cases, the analytical and numerical predictions based on an effective medium model are in good agreement with the measured data. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Negative refraction in a dielectric rod superlattice
Authors: Saado Y. , Neve‐Oz Y. , Golosovsky M. , Davidov D. , Frenkel A. 
Published: March 2007

AbstractWe studied microwave transmission, reflection, and refraction from a planar superlattice consisting of dielectric rods with two different diameters. This structural modulation results in a narrow transmission band inside the first photonic stopband. Band structure simulations indicate that this transmission band exhibits a negative phase velocity. We performed electric field mapping inside our superlattice, which revealed a negative phase velocity. In another setup we built a prism and studied transmission through it. We observed negative refraction, as expected for material with a negative refraction index. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Longitudinal capacitance design for optical left‐handed metamaterials
Authors: Schweizer H. , Fu L. , Gräbeldinger H. , Guo H. , Liu N. , Kaiser S. , Giessen H. 
Published: March 2007

AbstractTransmission line analysis of metamaterials gives clear and simple relations of the immittance Z (longitudinal impedance) and the admittance Y (shunt impedance) with the material parameters of permeability and permittivity, respectively. Beyond numerical analysis methods, TL analysis allows for a characterization of the handedness of lumped elements in the corresponding equivalent circuit. For achieving left‐handed materials, simultaneous negative permittivity and permeability are sufficient. Negative permittivity is normally realized through plasmonic oscillation of electrons in metals. A question remaining in optical left‐handed metamaterials is how to design properly a longitudinal capacitance, which is a left‐handed element indispensable for achieving a negative permeability. We propose a novel approach to design the longitudinal capacitance based on a metallic inductive/capacitive grating structure formed on a ridge patterned dielectric substrate. The fabricated structure shows the expected resonance and confirms the formation of the expected capacitance. Simulations show the possibility to obtain negative indices by adding additional metal strips up to frequencies of 300 THz and beyond, which depends on the structure size. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electromagnetic resonances in single and double split‐ring resonator metamaterials in the near infrared spectral region
Authors: Liu Na , Guo Hongcang , Fu Liwei , Schweizer Heinz , Kaiser Stefan , Giessen Harald 
Published: March 2007

AbstractWe investigate the resonant behavior of single and double split‐ring resonators (SRRs) in the near infrared regime. The resonance differences between single and double SRRs are explored both experimentally and numerically. The analysis based on reflectance spectra and numerical near‐field distributions shows that the resonant properties of a double SRR can be understood as a combination of two individual SRRs with different sizes. Additionally, we demonstrate interactions between the outer and inner rings. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thickness dependence of the optical properties of split‐ring resonator metamaterials
Authors: Guo Hongcang , Liu Na , Fu Liwei , Schweizer Heinz , Kaiser Stefan , Giessen Harald 
Published: March 2007

AbstractWe study the thickness dependence of the resonances of split‐ring resonators (SRRs) in the optical regime using experiments and numerical simulations. It is shown that the so‐called LC resonance frequency of an SRR increases with its thickness. We use inductor–capacitor (LC) circuits and a plasmonic model to analyze the resonant behavior of the SRR. The plasmonic interpretation based on an equivalent cut‐wire is proven to be a good model to describe the thickness dependence of the resonant behavior of the SRR in the optical regime. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)