低密度ポリエチレンの静水圧冷間押出し加工

概要

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The hydrostatic cold extrusion was carried out on low-density polyethylene (LDPE) with a die having die-angle of 45°, and characteristics of the extrusion, the effects of the extrusion conditions on the molecular orientation and mechanical properties of extruded LDPE were examined. Main results obtained are summerized as follows. (1) The extrusion proceeds at comparatively high rates at an initial stage, but the rate decreases gradually until the steady-state is reached. (2) An equation derived by Pugh and Low for the hydrostatic extrusion of metals can be apolied to LDPE extruded at low or high processing ratio. (3) The degree of crystallinity and size or crystallites decrease with increasing extrusion ratio, because of break down and disintegration of the fold-chain structure. (4) The crystalline orientation of extrudates is typically uniaxial one in which the <I>c</I>-axis orientation parallel to the extrusion axis becomes higher with increasing extrusion ratio. (5) The molecular orientation in the extrudates is uniaxial with cylindrical symmetry around the extrusion axis. (6) The tensile strength and Young's modulus of the extrudate increase monotonically with increasing extrusion ratio; and the elongation at break shows a prominent maximum at a relatively low extrusion ratio, then it decreases to a level.
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