Transient currents in poly(vinyl alcohol)–poly(vinyl pyrrolidone) polymer blend films

Abstract

Transient currents (charging and discharging currents) in poly(viny1 alcohol) (PVA)-poly(viny1 pyrrolidone) (PVP) polymer blend films were measured over the temperature range 30-150°C at field strengths of 2.32-23.2 x 106Vm-'. Polymer films were prepared by the isothermal immersion technique. Activation energies were evaluated from quasi-steady-state currents. A single relaxation peak was observed both from isochronal currents and low frequency dielectric relaxation. Activation energies evaluated from these two methods are found to be in fairly good agreement. The polarization is considered to be due to space charge origin along with some contribution from dipolar groups. The maximum loss was observed in Sample I (PVA : PVP = 25 : 79, suggesting maximum heterogeneity in this blend ratio.

Release of salicylic acid through poly(vinyl alcohol)/poly(vinyl pyrrolidone) and poly(vinyl alcohol‐g‐N‐vinyl‐2‐pyrrolidone) membranes

“…An important factor in the development of new materials based on polymeric blends is the miscibility between the polymers in the mixture, because the degree of miscibility is directly related to the final properties of polymeric blends 16. There are many studies related with the miscibility of PVA and PVP 14, 15, 17–23. Lu et al24 and Ping et al15 reported that PVA and PVP are miscible in any proportions in amorphous zones of the blends because of the hydrogen bonds between donor groups in PVA and acceptor groups in PVP.…”

Charging transient in polyvinyl formal

“…The current obtained immediately after the application of a step function voltage is known in most cases to decay with time until a steady state current is achieved (Lakshmi Narayana et al 1994). The discharging current flowing on removal of the voltage is usually the mirror image of the charging current except that a steady state current does not occur.…”