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Optical properties of simultaneous biaxially stretched poly(ethylene terephthalate) films
Author(s) -
Cakmak Mukerrem,
White James L.,
Spruiell Joseph E.
Publication year - 1989
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760292108
Subject(s) - materials science , refractive index , amorphous solid , poly ethylene , anisotropy , composite material , annealing (glass) , optics , principal axis theorem , ethylene , crystallinity , perpendicular , wavelength , optoelectronics , crystallography , geometry , biochemistry , chemistry , physics , mathematics , catalysis
We offer a detailed study on the anisotropic optical properties in uni and simultaneous biaxially stretched Poly(ethylene terephthalate) (PET) films. Cast amorphous sheets of PET were stretched to a series of extension ratios in two mutually perpendicular directions at 80, 90, and 100°C. Additionally, 0selected films were subsequently “heat‐set” by annealing with their width and lengths constrained. The principal refractive indices at sodium D wavelength of these, asstretched and heat‐set films were obtained using a modified Abbe refractometer. The changes in the principal refractive indices with the processing history were correlated with the orientation of PET chains and phenyl plane normals, which were determined independently by wide angle X‐ray (WAXS) pole figure technique.