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Annealing of ultra‐oriented high density polyethylene extrudates
Author(s) -
Tsuruta Akeharu,
Kanamoto Tetsuo,
Tanaka Koji,
Porter Roger S.
Publication year - 1983
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760230908
Subject(s) - materials science , extrusion , differential scanning calorimetry , annealing (glass) , composite material , small angle x ray scattering , high density polyethylene , thermal stability , polyethylene , ultimate tensile strength , microstructure , polymer , chemical engineering , scattering , physics , optics , thermodynamics , engineering
The annealing characteristics of highly‐oriented, high density polyethylene (HDPE) fibers extruded at 90°C to constant extrusion draw ratios (EDR) of 5.8 to 30 have been studied using small‐(SAXS) and wide‐angle (WAXD) x‐ray diffraction, differential scanning calorimetry (DSC), thermal shrinkage and tensile tests. The thermal stability in macroscopic properties, such as transparency, sample dimension, and tensile modulus, remarkably increases with the sample EDR. However, the folded chain crystals within microfibrils sensitively reorganize on annealing at ≥ 110°C, even when the macroscopic properties exhibit no significant changes at high EDR's. Although the EDR has a minor effect on the reorganizability of the fold chain crystals, it has a major influence on the SAXS intensity and the extended chain crystalline component detected by WAXD for both unannealed and annealed extrudates. This specific crystalline component has an improved thermal stability and enhances the thermal stability of macroscopic properties at higher EDR. The fibers extruded at 90°C in this study and those prepared at 134°C in a prior study, exhibit significantly different melting behavior after annealing and for long period vs . EDR relationships. These facts combined with the independent observations of the effect of annealing and extrusion temperatures on the consequent long period strongly suggest that annealing during extrusion plays an important role in determining the microstructure of extrudates, especially for extrusion near the ambient melting point of the polymer.