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A series of reactor powders of ultrahigh molecular weight (UHMW) polyethylenes with different morphology was melted at 160°C for 5 min and cooled in ice water. Low‐frequency Raman spectroscopy was used to characterize the straight‐chain‐segment (SCS) length distribution of both initial and melt‐crystallized materials. A bimodal SCS length distribution was found in the melt‐crystallized sample originated from the reactor powder with a very tenuous amorphous phase. In other samples recrystallized from powders with more ordered structure, the SCS length distribution was unimodal and approximately identical. The result is explained in terms of perfection of lamellar crystals formed under limited time and thermal conditions from differently organized initial structure. [ABSTRACT FROM AUTHOR]

Evolution of the straighten-chain-segment length distributions in three polyethylene reactor powders manufactured using different catalysts has been traced through the melting-drawing procedures carried out under the same temperature-deformation conditions. The powders exhibiting the presence of either folded or chain-extended crystalline entities yielded the oriented samples with quantitatively different interfibrillar structure, and, respectively, with different mechanical behavior concluded from their stress–strain curves and variation of the tangential modulus. The correlation between original and final properties of samples derived from reactor powders evidences a persistence of a kind of memory. The longitudinal disorder in nascent chain-extended crystals transforms virtually to the lateral disorder in the axially oriented interfibrillar material. [Copyright &y& Elsevier]