Polyethylene reactor powders with molecular weight ranging from 0.16 x 10(6) to 14.9 x 10(6) synthesized under various conditions have been subjected to drawing. The powders were compacted at controlled pressures and temperatures below their melting points. Compaction into plates was followed by two-stage solid-state drawing. The first stage was solid-state extrusion, the second was tensile drawing, both at controlled rates and temperatures below the melting point. It is found that the drawability of reactor powders depends sensitively on the polymerization temperature and conditions. Samples synthesized at 85-degrees-C in a slurry are highly drawable. In contrast, powders obtained at 30-degrees-C in the gas phase are not readily drawn. Molecular weight is found not to be the dominant factor in determining the drawing of reactor powder. Rather, it is the synthesis conditions, as they influence the interphase regions between crystals, that appear to control the limits of drawing. For the most favourable case among these samples, namely higher molecular weights and higher polymerization temperature, total draw ratios of nearly 100 and tensile moduli of 75 GPa were attained.
2-STAGE DRAWING OF HIGH-MOLECULAR-WEIGHT POLYETHYLENE REACTOR POWDER
OTTANI S;
1991
Abstract
Polyethylene reactor powders with molecular weight ranging from 0.16 x 10(6) to 14.9 x 10(6) synthesized under various conditions have been subjected to drawing. The powders were compacted at controlled pressures and temperatures below their melting points. Compaction into plates was followed by two-stage solid-state drawing. The first stage was solid-state extrusion, the second was tensile drawing, both at controlled rates and temperatures below the melting point. It is found that the drawability of reactor powders depends sensitively on the polymerization temperature and conditions. Samples synthesized at 85-degrees-C in a slurry are highly drawable. In contrast, powders obtained at 30-degrees-C in the gas phase are not readily drawn. Molecular weight is found not to be the dominant factor in determining the drawing of reactor powder. Rather, it is the synthesis conditions, as they influence the interphase regions between crystals, that appear to control the limits of drawing. For the most favourable case among these samples, namely higher molecular weights and higher polymerization temperature, total draw ratios of nearly 100 and tensile moduli of 75 GPa were attained.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
