Journal of Applied Polymer Science · 1987 · 49 citations · 11 references
Natural SciencesMaterials EngineeringMaterials SciencePolymer ChemistryPolymer EngineeringPolymer MaterialsCrystallization ProcessesPolymer CharacterizationPolymer Physical ChemistryPolymer PhysicsPolymer ProcessingPolymer ThermodynamicsCrystallinityCrystallinity AnalysisCrystallinity ChangesMeltingMelting EndothermMelting Of Polymer MaterialsPolyethyleneUltra-high-molecular-weight Polyethylene
Abstract On heating in DSC, samples of UHMWPE show a single, fairly sharp, melting endotherm which may be increased to a peak temperature of 147°C and 77% crystallinity by annealing at elevated temperatures. An irreversible conversion of nascent to folded crystals, between 134 and 142°C, was observed by heating nascent UHMWPE powder in the calorimeter. In the presence of n ‐hexatriacontane, the melting endotherm of UHMWPE was depressed and broadened and the conversion of nascent to melt‐crystallized polyethylene facilitated on heating. A melt‐crystallized mixture of ordinary linear polyethylene (HDPE) and UHMWPE was not resolved on remelting. After annealing this mixture for 12 h at 130°C, HDPE was fractionated and the melting of UHMWPE was sharpened. Crystals of UHMWPE, prepared from dilute solution in xylene, show a single sharp melting endotherm and high crystallinity, but the melting peak is reduced in temperature compared to nascent crystallized powder.
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