Three-phase characterization of uniaxially stretched linear low density polyethylene

摘要

This study comprises a detailed morphological study of cold-drawn polyethylene monofilaments by Raman spectroscopy, differential scanning calorimetry (DSC) and X-ray measurements. The structure of the three-phase morphology of the linear low density polyethylene monofilaments was investigated by combining these measurements. It was found that the most important structure variation was found in the intermediate or rigid amorphous phase, whereby the amounts of crystalline and amorphous phases were nearly constant and almost independent of the cold draw ratio. The intermediate third phase contains gauche and trans molecules and the amount of trans molecules was increased with the cold draw ratio and was directly related to this 2 cold draw ratio. The resulted mechanical properties of the oriented monofilaments are related to the amount of the trans content in the third phase, a result of the transformation of the gauche molecules into trans molecules due to the cold drawing of the monofilaments. It was found that the two peaks in the Raman spectra, respectively at 1303 and 1295 cm-1, can be correlated to the amount of gauche and trans molecules in the polyethylene monofilaments. A good and new insight into the three phase morphology was obtained by combining the DSC and X-ray measurements with the amounts of trans and gauche molecules from the Raman spectra analysis.