title: Broadband electric spectroscopy at high CO2 pressure: dipole moment of CO2 and relaxation phenomena of the CO2-poly(vinyl chloride) system.
abstract: Broadband electric spectroscopy (BES) is a technique that shows promise in studying the interactions of dense or supercritical gases with polymers, particularly with respect to chain mobility. Polymers that are treated with dense gases show a reduction in the viscosity, glass transition, and melting temperature. A high pressure cell for BES has been constructed that can be used from ambient temperature and pressure to 353 K and 15 MPa and over a frequency range from 20 Hz to 1 MHz. In the past, the dielectric constant of CO(2) was determined by measurements at only one or two frequency values. New instrumentation and technology allow this experiment to be expanded to cover a wider frequency range. BES measurements of CO(2) do not show any relaxation peaks in the permittivity from 20 Hz to 1 MHz and 1 to 6 MPa. By these measurements, the CO(2) dielectric constant was evaluated between 0.1 and 6 MPa. Cell testing with poly(vinyl chloride) (PVC) at 323 K and CO(2) pressures from 0.1 to 13 MPa indicate an increase in the chain segmental motion at high pressures resulting from a reduction in the glass transition temperature of the PVC-CO(2) system due to plasticization by CO(2).
authors.affiliation: Department of Chemical Sciences, University of Padua, Via F. Marzolo 1, I-35131 Padova, Italy. vito.dinoto@unipd.it
authors.forename: Vito
authors.initials: V
authors.lastname: Di Noto
authors.forename: Keti
authors.initials: K
authors.lastname: Vezzù
authors.forename: Fosca
authors.initials: F
authors.lastname: Conti
authors.forename: Guinevere A
authors.initials: GA
authors.lastname: Giffin
authors.forename: Sandra
authors.initials: S
authors.lastname: Lavina
authors.forename: Alberto
authors.initials: A
authors.lastname: Bertucco