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Distribution of higher‐order structures in injection‐molded polypropylenes
Author(s) -
Fujiyama Mitsuyoshi,
Wakino Tetsuo
Publication year - 1991
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.1991.070430108
Subject(s) - materials science , composite material , crystallinity , flexural strength , orientation (vector space) , molding (decorative) , melt flow index , cylinder , relaxation (psychology) , polymer , geometry , psychology , social psychology , mathematics , copolymer
Abstract Flexural test specimens were injection‐molded from six homoisotactic polypropylenes with MFI = 0.49‐25.1 dg/min under cylinder temperatures of 200‐320°C. Distributions in the flow direction of higher‐order structures such as crystallinity X c , thickness of skin layer, a* ‐axis‐oriented component fraction [ A* ], and crystalline orientation functions and distributions in the thickness direction of higher‐order structures such as X c , β‐crystal contents, [ A* ], and crystalline orientation functions were studied. These higher‐order structures are inhomogeneous in the flow and thickness directions, which strongly influences the product properties such as mechanical and thermal properties. Molecular orientation process in injection molding was theoretically analyzed from a viewpoint of growth of recoverable shear strain at the gate and its relaxation in the cavity, which could considerably well explain the variations in the flow and thickness directions of the quantities such as thickness of the skin layer and crystalline orientation functions which express the degree of molecular orientation.