The influence of pressure on dielectric relaxation for phthalate derivatives in the supercooled state

The dielectric relaxation of phthalate derivatives in the supercooled state has been studied at pressures up to 300 MPa, covering a frequency range from to . The behaviour of the relaxation time is very well reproduced by the relation . The analysis of the absorption curves shows that pressure increases the amplitude of the -relaxation more than the equivalent temperature change. The scaling form presented by Dixon and co-workers for the -process in supercooled liquids is re-examined in the light of pressure - dielectric relaxation data. It was found that Dixon scaling distinguishes isothermal measurements from isobaric measurements, by means of the greater strength of the second relaxation process for the pressure path.