Infrared technique for the measurement of structural changes during the orientation process in polymers

Polarized infrared measurements were made on polymer samples to obtain the structural changes occurring during the orientation process. The absorbances of the infrared bands were measured by determining the three components of the absorbance. Two components were obtained directly with plane‐polarized light while the third is obtained by tilting the sample and extrapolating. Corrections were made for machine optics polarization, sample birefringence, polarizer inefficiency, anisotropy of the index of refraction, and scattering from the film surface. Data are reported for polyethylene obtained from cold‐drawn specimens as a function of draw temperature. Polyethylene exhibits no strain‐induced crystallization as a result of the chain‐alignment process. Annealing of the drawn samples reperfects the distorted crystals.