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SYNOPSISThe cooling of the spinning stage in a commercial compact-spinning line has been studied. A rectangular fiber bundle is extruded from the spinneret and cooled by air entering from one side. The speed of the cooling air is considerably reduced through the fiber bundle. There are practical lower and upper limits for the cooling air entrance speed, corresponding to filament breakage a t the leeward and windward sides, respectively. These limits are functions of the material and processing parameters. Due to the nonuniform cooling, fibers sampled at the windward side generally have higher molecular orientation, lower amorphous fraction, higher density, and higher tensile modulus and strength. For most combinations of spinning and material parameters, the structure is either bimodally oriented a-crystalline or uniaxially oriented mesomorphic a t all spinneret positions. Fibers with different structure types show opposite windward/leeward side trends with regard to local order and melting behavior. The structure may be mesomorphic a t the leeward side and a-crystalline at the windward side, if the average spin-line stress is close to a critical value for orientationinduced crystallization, and the air speed difference across the spinneret is large. The cooling air speed affects the spin-line stress. Hence, the fiber-to-fiber variations due to nonuniform cooling are discussed in terms of the molecular orientation in the melt and the effective time available for arranging molecules into ordered structures. 0 1995 John Wiley & Sons, Inc.

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It is important to get increased knowledge on how extruded insulation perform under HVDC ageing. In this work low density polyethylene with and without an antioxidant additve was subjected to thermal and electrical ageing. During ageing the crystallinity increased in both materials but no changes in the oxidation level was observed. The antioxidant additive had a major effect on the space charge accumulation during ageing.