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Morphology and thermal expansion in large HDPE injection moldings
Author(s) -
Leung Mathew,
Gnatowski Marek,
Sun Grace,
Stanese Adrian,
Wong Tonny
Publication year - 2019
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.47507
Subject(s) - materials science , composite material , scanning electron microscope , differential scanning calorimetry , thermomechanical analysis , anisotropy , crystallinity , thermal expansion , core (optical fiber) , molding (decorative) , spherulite (polymer physics) , glass transition , optical microscope , birefringence , polymer , optics , physics , thermodynamics
Morphology and linear coefficients of thermal expansion (LCTE) within the wall of a large (10 kg) injection molded container were evaluated. The study employed polarized light microscopic birefringence techniques, differential scanning calorimetry, scanning electron microscopy (SEM), as well as thermal mechanical analysis to determine the LCTE anisotropy in the skin and core of the wall. A difference in crystallinity between skin and core was found, and a region with distinct lamellas was seen under SEM without sample etching. A large variability in anisotropy of the LCTE was found in the relatively thick (~700 μm) skin of the molding. The LCTE differences between skin and core were attributed to molecular orientation related to resin flow. LCTE anisotropy as an important source of residual stress in the transition zone between skin and core was confirmed by fractographic analysis. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47507.