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Thermal and electrical properties of some epoxy based composites
Author(s) -
Bánhegyi György,
Szaplonczay Pál,
Frojimovics Gábor,
Karasz Frank E.
Publication year - 1990
Publication title -
polymer composites
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.577
H-Index - 82
eISSN - 1548-0569
pISSN - 0272-8397
DOI - 10.1002/pc.750110302
Subject(s) - materials science , composite material , epoxy , glass transition , dielectric , thermal stability , space charge , differential scanning calorimetry , polymer , physics , optoelectronics , quantum mechanics , electron , thermodynamics
Abstract 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 T g 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.