A simple evaluation method of stress-optical coefficient of polymers

Abstract

The stress-optical coefficient characterizes the birefringence of flowing material and an optical measurement of flowing liquid is required for its evaluation. Here we propose a simple method in which the measurement for liquid is not involved. A polymer film is stretched a few percents under a constant stress at approximately its glass transition temperature and slowly cooled down to the room temperature; the remaining birefringence of the solid film is measured. The birefringence divided by the stress (= the load /final cross sectional area) gives the stress-optical coefficient of flow birefringence. The theoretical basis for this proposal, the result of experimental test, and the difficulty in some cases are described.