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Internal stress, molecular orientation, and distortion in injection moldings: Polypropylene and glass‐fiber filled polypropylene
Author(s) -
Hindle C. S.,
White J. R.,
Dawson D.,
Thomas K.
Publication year - 1992
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.760320302
Subject(s) - materials science , polypropylene , composite material , residual stress , distortion (music) , stress (linguistics) , anisotropy , stress relaxation , glass fiber , perpendicular , optics , creep , optoelectronics , amplifier , linguistics , philosophy , physics , geometry , cmos , mathematics
Residual stress measurements and distortion analyses have been conducted on injection molded plaques made from polypropylene (PP) and a short glass‐fiber filled polypropylene (GFPP). The residual stress analyses include measurements both parallel and perpendicular to the direction of flow during mold filling. Residual stresses are very anisotropic in GFPP, but not in PP. The residual stress levels in PP fall on aging at room temperature, whereas in GFPP the proportion of stress relaxation is smaller, and significant stresses remain even after heating to elevated temperatures. A significant contribution to distortion has been linked to the ejection process, and the long‐ and short‐term distortion of moldings is discussed within the framework of the properties of the materials measured here.