Low birefringence measurement in polymers

Many polymer films are filled with particles to either increase the surface roughness or to increase the strength of the film. Occasionally, however, impurities are present in unfilled films and these can cause problems such as tearing. It is possible to use the birefringence in the polymer to try and identify the onset of voiding and tearing. Methods for the determination of low birefringence were studied and a full field automated technique based on phase stepping used to analyse polymers with inclusions.