A comparison of the determination of macromolecular orientation in polypropylene by attenuated total‐reflection fourier‐transform infrared spectroscopy and X‐ray diffraction

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Abstract
Attenuated total reflection‐infrared (ATR‐IR) spectroscopy and wide‐angle x‐ray diffraction (WAXD) were used to determine the macromolecular orientation of a series of six uniaxially oriented polypropylene sheets with elongations of 0% to 500%. The orientation functions were expressed as fractions of chains oriented along the machine, trasverse, and normal directions in the sheets. Good agreement was found between the orientation functions for the two techniques. Sources of potential difference between the two techniques were discussed. The ATR‐IR technique is surface sensitive to a depth of about 5 or 10 μm into the surface while the WAXD technique is bulk sensitive. The ATR‐IR technique is sensitive to both the crystalline and noncrystalline material while the XRD technique is sensitive only to the crystalline material.