Anomalous high-infrared reflectance of extruded polyoxymethylene

Abstract

Polarized infrared (IR) reflectance measurements were performed on polyoxymethylene (POM) prepared by the extrusion method, and an abnormally high reflectance of ∼90% was observed along the extruded direction in the 1000 cm−1–900 cm−1 region. High reflectivity was found in samples made by the conventional injection molding. However, the response of the extrusion sample was higher than that of the injection sample, which can be attributed to the Reststrahlen band. The relative permittivity calculated from the polarized reflection spectrum of the extruded direction shows a notably deep negative region in this high reflectance frequency. Using x rays, by differential scanning calorimetry, and by field emission scanning electron microscopy characterization, the difference in crystallinity and morphology from the extrusion and the injection molding plate was investigated, and the difference in IR optical response was discussed. The conventional IR band assignment of POM was also discussed.

Structural Analysis of Injection-Molded Polyoxymethylene Treated Below a Melting Point Using Field-Emission Scanning Electron Microscopy and Infrared Spectroscopy

“…This dip should appear due to the interface effect between the crossed component and the matrix since the dip frequency position is close to the LO mode if we regard the E 1 (8) mode as a surface polariton. 22,36 Furthermore, the mode has a negative region in the real component of the RP, which supports the dip structure originating from the surface polaritons. The spectral shape can be produced to some extent (Fig.…”

“…This peak position is used to judge the POM mesostructure: namely, ECC or FCC. 36 Because all ε r,2 peaks are positioned above 900 cm À1 , the primary mesostructure in our sample is FCC, even after the heat treatment. Moreover, we show the half-width of ε r,2 parallel to the injection direction.…”

“…In addition, the lowest absorption peak occurs at ∼902 cm −1 , which suggests that an FCC mesostructure in the POM. 36…”

“…22 On the other hand, a streak-like morphology is observed in addition to the nest structures when the POM is produced by extrusion molding. 36 A high reflectance of approximately 90% was observed in some places in the extrusion sample, and the real component of the RP showed an extremely deep negative value. Examining these structures revealed that the injection molding had an FCC structure, whereas the extrusion molding mainly had an ECC structure.…”

“…In addition, the lowest absorption peak occurs at ∼902 cm À1 , which suggests that an FCC mesostructure in the POM. 36 The submicron structure that appears in FE-SEM is much smaller than the IR wavelength of ∼10 µm, but the EM model cannot explain the polariton mode. This suggests, for materials with large frequency dispersions, the polariton is very sensitive to submicron phase interfaces.…”