POLARIZED INTERNAL REFLECTANCE SPECTROSCOPIC STUDIES OF ORIENTED POLY(ETHYLENE-TEREPHTHALATE)

Polarized internal reflectance spectroscopy (IRS) has been used to evaluate molecular orientation and crystallinity of poly(ethylene terephthalate) film surfaces. Measurements were taken using samples stretched in both uniaxial and biaxial modes. All bands of interest were normalized with a reference band near 1410 cm(-1), resulting from phenylene ring vibrations. Normalization was performed in order to overcome problems with sample contact and effective thickness. Results obtained using bands representing trans and gauche rotational isomers, present, respectively, at 1340 and 1370 cm(-1), have been related to data acquired using density and birefringence techniques. The polarized IRS technique discussed is well suited for investigations of polymer orientation and crystallinity, since it avoids limitations related to sample thickness and clarity imposed by polarized transmission infrared spectroscopy. Parameters such as orientation functions, attenuation indices, dichroic ratios, and structural factors have been determined from data collected in each of the three spatial directions. Results are correlated with corresponding density, birefringence, and refractive index values and are found to give good agreement with these methods. (C) 1994 John Wiley & Sons, Inc.