Application of ATR-IR to the Analysis of Surface Structure and Orientation in Uniaxially Drawn Poly(Ethyleneterephthalate)

A critical examination of the use of ATR-IR for the examination of surface composition and orientation in uniaxially drawn poly(ethyleneterephthalate) (PET) films has been performed. This work has identified the band at 1410 cm⁻¹ as a satisfactory reference band in ATR-IR analyses for surface composition and orientation analyses in oriented PET films. Other commonly used reference bands at 790 and 1510 cm⁻¹ have been shown to be influenced by both incident infrared polarization and orientation within the polymer films. Control of sample clamping pressure in a conventional ATR-IR clamp has been shown to afford optimized sample contact, needed in conjunction with the use of valid reference bands to obtain reproducible in-plane surface dichroism measurements of films with varying degrees of orientation.