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Far infrared (FIR) birefringence is a new tool for measuring orientation in semicrystalline polymers. In this work FIR birefringence of high‐pressure injection‐molded high‐density polyethylene (HDPE) was compared with wide‐angle X‐ray scattering (WAXS) and shrinkage for the first time. An indirect measure of orientation was obtained by differential thermal analysis (DTA). The content of high‐temperature melting crystals was found to increase with increasing orientation. A high correlation was found between FIR birefringence and the other orientational measurements. Contrary to the other orientational methods used, FIR birefringence does not saturate with highly oriented samples. It is furthermore faster, nondestructive, and can be used for probing fairly thick samples.
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Boldizar et al. (1988) studied this question.
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