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ABSTRACT:The combination reaction of linear low density polyethylene initiated by Dicumyl peroxide at elevated temperature was investigated under different steady shear rates. Gel-permeation chromatography was used to determine the molecular weight distributions, and time-molecular weight superposition method was used to analyze the viscosity curves. The results showed that lower (or higher) shear rate increased the reaction possibility of shorter (or longer) chains.

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The three stages in the hot-drawing process of ultrahigh-molecular-weight polyethylene gel films can be detected by x-ray diffraction, infrared spectroscopy, birefringence and scanning electron microscopy. In the first stage of the drawing process, the lamellae in the gel films rotate and/or slip with the b-axis preferentially perpendicular to the drawing direction. With increased drawing, the c-axis of the lamellae become parallel to the stretching direction while unfolding of the chain begins, and the chains of the amorphous phase also orient along the drawing direction in the strain-chain domain. When the draw ratio is large enough, the lamellar structure is transformed into a fibrillar structure in a two-dimensional fashion.