Effects of glow-discharge nitrogen-plasma on the linear birefringence of polyester sheets

A simple white light interferometric method is used to study the effects of plasma on the steady-state linear birefringence of polyester sheet films. Glow-discharge nitrogen-plasma of power 13 W with nine different exposure times from 0 to 25 min is applied to films of 0.22 mm thickness. The relationship between the linear birefringence and some atomic parameters is derived theoretically and tested experimentally. Effects on the linear birefringence, the linear retardance and Herman's orientation parameter are investigated. The increase of plasma exposure time produces an increase in the linear birefringence and Herman's orientation parameter. Characterization of plasma-treated and plasma-untreated polyester samples have been thoroughly examined using Fourier transform infrared (FTIR) spectroscopy. It is noted that no new bands have appeared after treatment for all the tested samples at different time intervals. There is an increase in intensity and band definition, and a shift of some bands that were already present in the spectrum of the untreated sample, assigned to the trans conformer.