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  • 1
    Electronic Resource
    Electronic Resource
    Effect of frequency and temperature on dielectric properties of polystyrene at microwave frequencies (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 184 (1991), S. 55-68 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die dielektrischen Eigenschaften von Polystyrol wurden zwischen -120 und +160°C bei drei Frequenzen im Mikrowellenbereich untersucht. Die Meßtechnik basierte auf der von Dakin und Works modifizierten Kurzschlußwellenleiter-Methode nach Roberts und von Hippel für Material mit niedrigen und mittleren Verlustmoduli. Zwei verschiedene Relaxationsmechanismen wurden identifiziert, die von der Hauptkettenbewegung und den Rotationsschwingungen der Phenylringe herrühren. Aktivierungsenergien und Dipolmomente wurden berechnet, interpretiert und mit Literaturwerten verglichen.
    Notes: Ambient dielectric measurements as functions of frequency in X-band microwave region have been made on solid samples of polystyrene. Effects of temperature (-120 to +160°C) at three different frequencies have also been studied. The measurement technique applied based on short-circuited waveguide method of Roberts and von Hippel modified by Dakin and Works for low loss and medium loss samples. Two different types of relaxations are identified originating from main chain motion, wagging, and rotational motions of pendent phenyl group. Intrinsic activation energy for polystyrene molecule, dipole moment per repeat unit, and the average apparent energy of a polystyrene molecule associated with its induced transient dipoles have also been calculated and the data so obtained are explained and compared with standard literature.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051840106
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  • 2
    Electronic Resource
    Electronic Resource
    Studies on miscibility of blends of thermoplastic polyurethane and poly(ethylene-co-methyl acrylate) (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 213 (1993), S. 7-13 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Blends aus einem thermoplastischen Polyurethan auf Polyetherbasis und Poly(ethylen-co-methylacrylat) wurden durch Schmelzemischen und anschließendes Formpressen hergestellt. IR-spektroskopische Untersuchungen und dynamische-mechanische Messungen zeigen, daß die Polymeren im gesamten Mischungsbereich mischbar sind.
    Notes: Blends of polyether-based thermoplastic polyurethane (TPU) and poly(ethylene-co-methyl acrylate) (EMA, 21 wt.-% MA) were prepared by melt mixing and subsequent compression moulding. Infrared spectroscopy studies and dynamic mechanical analysis reveal that the polymers are miscible in the entire composition range.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1993.052130102
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of electron beam radiation on structural changes of trimethylol propane trimethacrylate, ethylene vinyl acetate, and their blends (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 1329-1341 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of electron beam irradiation at different radiation doses (2, 5, 10, 15, and 20 Mrad) on trimethylol propane trimethacrylol propane trimethacrylate (TMPTMA), ethylene vinyl acetate (EVA, 12% vinyl acetate content), and their blends (0.5, 1, 1.5, 2, 2.5, 3, and 5 parts/100 parts EVA) was investigated. An IR study showed some residual unsaturations retained in irradiated pure TMPTMA, while in blends all unsaturations were used up at a very early stage of irradiation. The concentration of the carbonyl group due to air oxidation increased in pure EVA and blends, but it reached a maximum at the 1.5-part TMPTMA level and 5-Mrad dose. some ether linkages were formed during irradiation in pure EVA and the blends, although in pure EVA the concentration of ether linkages reached a maximum at the 2-Mrad dose and then decreased and in the blends it increased with an increase in radiation dose. Gel content showed an increasing trend with an increase in radiation dose, but it increased marginally with TMPTMA level. A blend of EVA with 1 part TMPTMA produced more gel than pure EVA at the same irradiation dose. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Electron-beam-initiated grafting of triallyl cyanurate onto polyethylene: Structure and properties (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 141-150 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Electron-beam (EB)-initiated grafting of triallyl cyanurate (TAC) onto polyethylene (PE) has been carried out over a range of radiation dose (2-20 Mrad) and concentrations of TAC (0.5-3 parts by weight). The grafting level, as determined from IR spectroscopy, is maximum at a 10 Mrad radiation does using 1 part TAC. With increasing TAC level at a 15 Mrad dose, the grafting level is higher only after 1.5 parts TAC. The gel content increases with radiation dose in the initial stages. X-ray studies indicate two peaks at 10.6-10.8° and 11.7-11.9° and the corresponding interplaner distances of 4.15 and 3.80 Å. With increase in radiation dose or TAC level, the crystallinity decreases in the initial stage and then increases. It shows a decreasing trend again at higher radiation dose. The interplanar distance or the interchain distance of the modified polymer does not change. However, the crystallite size increases initially and then decreases. The tensile properties are relatively insensitive to the variation of radiation dose because of the interplay of various factors. The dielectric loss, tan δ, shows a maximum at a 10 Mrad dose and minimum at 5 and 15 Mrad due to changes of polarity and the carrier mobility. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530202
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  • 5
    Electronic Resource
    Electronic Resource
    Dielectric behavior of polystyrene foam at microwave frequency (1980)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 20 (1980), S. 441-446 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polystyrene foams have been generated and fabricated into differently shaped structures', by change of steaming period under constant impregnation time and solvent-nonsolvent composition. Optical photomicrographs of samples both plain and wax-copper-coated reveal uniform appearance, distinct grain-boundaries, and random cell size distribution. Dielectric measurements have been made on test specimens cut according to wave-guide size at 9.375 GHz X-band microwave frequency by short-circuited wave-guide method of Smith and Hippel modified by Dakin and Works. Dielectric constants are linear, on direct and semi-log scales in bulk-density and volume-fraction, obeying Weiner's inequalities. Formulae of Landau-Lifshitz, Beer, Maxwell-Wagner, Odelevsky, etc. have been tried. Data fit best with the logarithmic law of Lichtenecker and Rother. Specific polarization is also a true function of density. Dielectric constant vs bulk-density plots of foams resemble dielectric-constant vs fractional-density plots based on the theoretical derivation by Smith for polystyrene compacts, signifying that compacts containing closely-spaced oblong-spherical particles arc physically similar to foams having spherical gas inclusions in plastic structures. Tan δ lying in the range 0.002-0.0038 results from conformational polarization (β-relaxation at room-temperature for wide-angle torsional oscillations of side-groups with co-operative motion from wriggling chains). It is therefore possible for low-loss foam dielectrics suitable for micro-wave applications to be made by this method.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760200610
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  • 6
    Electronic Resource
    Electronic Resource
    Microwave dielectric and mechanical behavior of foams from polystyrene and poly(methyl methacrylate) blends (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 32 (1986), S. 3551-3564 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Foams have been generated from blends of polystyrene and poly(methyl methacrylate) under identical conditions of solvent-nonsolvent ratio, impregnation time, and heating period. Scanning electron micrographs of copper-coated fractured surfaces of the samples reveal a distinct transition in their structures from a more or less homogeneous cell-size distribution with prominent grain boundaries to complete lack of foaming and cellularity through random dispersions of spherical poly(methyl methacrylate) inclusions in polystyrene-foam matrix. Dielectric measurements have been made on test specimens at 9.375 GHz X-band microwave frequency by the method of Smith and Hippel modified by Dakin and Works. Percent porosity is the least at 20 wt% of polystyrene while foam density linearly decreases with percent porosity. Dielectric constant is linear in foam density on direct and semilog scales (passing through unity and zero, respectively), in blend composition and also in percent porosity. Dielectric constant increases with increase of foam density or weight percent of polymethyl-methacrylate and decreases with increase of percent porosity. The dielectric constant is, however, nonlinear in volume fraction of polystyrene on both direct and semilog scales, obeying Weiner's inequalities. The logarithmic law of Lichtenecker and Rother with an empirical factor 0.8276 in the index fits the data best. Specific polarization is minimal at 60 wt% of polymethyl methacrylate. The calculated Bottcher-Bruggleman plot based on the interacting spherical particle model is found to be of limited applicability. This is explained on the basis of long-range intra- and intermolecular dipole-dipole interactions. The pattern of the change of dielectric loss tangent (tan δ), lying in the range 0.150-0.045 and attaining a minimum at 20 wt% polystyrene, has similarly been explained in terms of α and β relaxations due to conformational rearrangements and steric hindrances of rotations. The compressive strength measured as a function of composition shows that the reinforcement depends on an optimization between the degree of cellularity and packing.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1986.070320215
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  • 7
    Electronic Resource
    Electronic Resource
    Dielectric behaviour of styrene-methyl methacrylate copolymer foams at microwave frequenciesA part of this paper was presented at the 28th IUPAC symposium held at the University of Massachusetts, Amherst, USA, from July 12 to 16, 1982. (1984)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 120 (1984), S. 61-72 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Dielektrische Effekte wurden mit Hilfe der kurzgeschlossenen Wellenleiter-Methode im Mikrowellenbereich bei 9,375 GHz an Schäumen aus Copolymeren, die Styrol und MMA in verschiedener Zusammensetzung enthielten, untersucht. Sie wurden unter gleichen Bedingungen in bezug auf Lösungsmittel/Fällungsmittel, Imprägnierungszeit und Dampfbehandlungsdauer hergestellt. Die Ergebnisse wurden mit der Schaumdichte korreliert; die Porosität und die Zusammensetzung wurde anhand der Dipol-Dipol-Wechselwirkungen und der Anwendbarkeit von Wieners Gesetz sowie anhand des logarithmischen Gesetzes von Lichtenecker und Rother mit einem empirischen Faktor von 0,64 basierend auf dem Gesetz der Additivität von Mischungen und der Beziehung von Böttcher-Bruggeman interpretiert. Rasterelektronenmikroskopische Aufnahmen von mit Kupfer überzogenen Bruchflächen der Proben wurden gemacht, um den Grad der Schäumbarkeit, die Zellenverteilung und den Versagensmechanismus zu prüfen. Die Mikrohärte, die Kompressions- und die Biegefestigkeit wurden ebenfalls bestimmt. Die Verlust-Charakteristika wurden in ähnlicher Weise der Schäumbarkeit und der Orientierbarkeit der Dipole zugeschrieben. Eine richtige Wahl des Reaktivitätsverhältnisses der Monomeren führt zu einer optimalen Verstärkung und zu guten dielektrischen Werten für die Anforderungen in bezug auf Elektronik und Radartechnik.
    Notes: Ambient dielectric effects were studied by the short-circuited waveguide method at 9.375 GHz microwave frequency in foams from copolymers of styrene and methyl methacrylate of varying compositions, generated under identical conditions of solvent-nonsolvent ratio, impregnation time and steaming period. The results were correlated with foam-density, porosity and composition and were interpreted in terms of dipole-dipole interactions and the applicability of Wiener's inequalities, logarithmic law of Lichtenecker and Rother with an empirical factor of 0.64 in the index based on the additive law of mixtures and the Böttcher-Bruggeman's relation. Scanning electron micrography on copper-coated fractured surfaces of the samples was done in order to examine the degree of foamability, cell-size distribution and the mechanism of failure. Microhardness, compressive and flexural strength were also measured. Loss characteristics were similarly ascribed to copolymer foamability and dipoleorientability. A prudent choice in the monomer reactivity ratio might therefore yield an optimum reinforcement and a proper dielectric requirement suitable for electronic and radar device constructions.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1984.051200103
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