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Viscoelastic flow analysis of surface morphology on injection‐molded polypropylene
Author(s) -
Kobayashi Yutaka,
Otsuki Yasuhiko,
Kanai Toshitaka
Publication year - 2010
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.21752
Subject(s) - materials science , composite material , viscoelasticity , birefringence , polypropylene , flow birefringence , deformation (meteorology) , flow (mathematics) , molding (decorative) , natural rubber , layer (electronics) , polymer , optics , mechanics , physics
The molecular orientation of a frozen layer in an injection‐molded specimen of a polypropylene–rubber blend was investigated. A typical V‐shaped pattern of birefringence was observed from the surface to the core in a crosscut section. From the comparison of the V‐patterns near the gate to the flow end, it was assumed that a frozen layer formed from the surface to a depth of 0.06 mm in a plaque (3 mm thickness) during the injection molding filling process. Numerical viscoelastic analysis of the fountain flow was carried out using an original 2D unsteady flow simulation program and ignored crystallization. A large extensional deformation formed just when the molten polymer contacted the cavity wall and the deformation immediately froze. A layer with a small birefringence between the surface and the shear‐oriented layer was divided into two parts. The depth profile of birefringence was compared to the principal stress difference calculated by numerical analysis. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers