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Digitale Medien

Effects of phase separation on the mechanical properties of polystyrene/poly(vinyl methyl ether) blends (1991)

Kim, J. H. ; Karasz, Frank E. ; Malone, M. F.

Stamford, Conn. [u.a.] : Wiley-Blackwell

Polymer Engineering and Science 31 (1991), S. 981-987

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ISSN: 0032-3888

Schlagwort(e): Chemistry ; Chemical Engineering

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: The effects of phase separation temperature and time on the tensile, dynamic mechanical, and tear properties of blends of polystyrene and poly(vinyl methyl ether) were investigated after phase separation above their respective cloud points with specified temperature-annealing time protocols. The results are analyzed in terms of the phase connectivity, interfacial adhesion, and changes in the glass transition temperature.

Zusätzliches Material: 12 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pen.760311308

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Digitale Medien

AC and DC dielectric properties of some polypropylene/calcium carbonate composites (1990)

Bánhegyi, György ; Karasz, Frank E. ; Petrović, Zoran

Stamford, Conn. [u.a.] : Wiley-Blackwell

Polymer Engineering and Science 30 (1990), S. 374-383

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ISSN: 0032-3888

Schlagwort(e): Chemistry ; Chemical Engineering

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: AC dielectric properties and thermally stimulated polarization (TSP) and depolarization (TSD) currents were studied in a series of CaCO3-filled polypropylene composites. The filler content (0 to 50 weight percent) and the average particle size (3.0 to 16.1 μm) at constant filler content (30 weight percent) were varied in separate groups of samples. In a third group of samples the filler (20 to 40 weight percent) was surface treated with stearates. The AC dielectric behavior of composites containing untreated fillers is largely determined by a small amount of adsorbed water. Upon heating, the dielectric properties show maxima (increasing with decreasing frequency) which disappear on cooling. In the case of stearate-treated fillers the dielectric loss level is higher, the dispersion and loss curves on heating reflect a combination of dipolar and protonic processes with water desorption. In the dry state the onset of an audio frequency relaxation process is observed in the pre-melting zone. The thermally stimulated currents of the composites containing treated and untreated fillers are also different. In the case of the untreated fillers the TSP curves show maxima indicating water desorption which are increasingly intense and roughly exponential with filler content. The high temperature conductivity and the intensity of the pre-melting depolarization peak pass through a minimum as a function of filler content. Above 20 weight percent filler content the activation energy of high temperature conductivity decreases. In the case of the surface treated samples, the thermally stimulated response is different for “wet” and dried samples. The dry samples exhibit a relaxation between the amorphous and crystalline transitions of the matrix polymer which is probably due to interfacial relaxation caused by the enhanced surface conductivity of the stearate-treated fillers.

Zusätzliches Material: 15 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pen.760300609

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Digitale Medien

Thermal and electrical properties of some epoxy based composites (1990)

Bánhegyi, György ; Szaplonczay, Pál ; Frojimovics, Gábor ; [weitere]

Brookfield, Conn. : Wiley-Blackwell

Polymer Composites 11 (1990), S. 133-143

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ISSN: 0272-8397

Schlagwort(e): Chemistry ; Chemical Engineering

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Maschinenbau

Notizen: Thermally stimulated creep compliance, differential scanning calorimetric behavior, thermal degradation, AC dielectric permittivity and loss (between 120 Hz and 100 kHz) and thermally stimulated polarization and aepolarization currents were studied in a cycloaliphatic epoxy resin (B), in a conventional bisphenol-A-diglycidyl ester type epoxy resin (C) and in composites consisting of: resin B/wollastonite (B/W), resin B/quartz (B/Q) and resin C/wollastonite (C/W). The filler content was 60 wt%. Resin B exhibited higher Tg and lower rubbery deformability than resin C due to its more compact structure. Fillers reduced the rubbery deformation and thermal expansion and shifted the transition temperatures by a few degrees. The shift depended on the method used. Composites B/W and C/W exhibited higher thermal stability than the corresponding pure resins, while sample B/Q was less stable than resin B. Resins B and C exhibited a low temperature β transition (in the case of resin B a doublet) and a high temperature α or glass transition. AC dielectric losses were fairly similar in samples B and B/W, while the high temperature loss of sample B/Q was determined by a space charge process probably due to the matrix/filler interface. In samples C and C/W the α transition is visible but it is superposed on a strong space charge process due to the resin/electrode interface. Thermally stimulated currents show a behavior qualitatively in agreement with the AC results but the very low effective frequency and the nonlinear field strength dependence of the space charge processes cause some minor differences.

Zusätzliches Material: 18 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pc.750110302

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