Title :
Influence of temperature and pressure on the dynamics of glass formers explored by dielectric spectroscopy
Author :
Casalini, R. ; Capaccioli, S. ; Presto, S. ; Lucchesi, M. ; Rolla, P.A. ; Corezzi, S. ; Paluch, M.
Author_Institution :
Dipartimento di Fisica, Pisa Univ., Italy
fDate :
6/1/2001 12:00:00 AM
Abstract :
The dynamics of the epoxy compound polyphenyl-glycidyl-ether-coformaldehyde was investigated by wideband dielectric spectroscopy (10-2 to 1010 Hz) by varying either pressure or temperature. The measurements were undertaken in two different conditions: under isobaric condition (atmospheric pressure) varying temperature down to the supercooled and glassy phases and under isothermal conditions by changing the pressure from 0.1 to 270 MPa. The analysis of the structural relaxation time behavior either varying the temperature or the pressure was found to agree well with a previously derived expression for τ(T, P) based on a cooperative model. In particular it was found that with a unique set of parameters it is possible to describe the 2-dimensional surface τ(T, P) over a wide range of temperature and pressure. This result agrees well with the observed independence of the fragility in both isothermal and isobaric conditions
Keywords :
dielectric losses; glass transition; polymer blends; polymer structure; 0.1 to 270 MPa; 1E-2 to 1E10 Hz; 2-dimensional surface; cooperative model; epoxy compound; glass formers; isobaric condition; isothermal condition; polyphenyl-glycidyl-ether-coformaldehyde; structural relaxation time; wideband dielectric spectroscopy; Atmospheric measurements; Dielectric measurements; Electrochemical impedance spectroscopy; Glass; Isobaric; Isothermal processes; Phase measurement; Pressure measurement; Temperature; Wideband;
Journal_Title :
Dielectrics and Electrical Insulation, IEEE Transactions on
