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Influence of processing on quality of injection‐compression‐molded disks
Author(s) -
Yang S. Y.,
Ke M. Z.
Publication year - 1995
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.760351503
Subject(s) - materials science , compression (physics) , compression molding , composite material , shrinkage , mold , molding (decorative) , birefringence , expanded polystyrene , residual stress , polystyrene , optics , polymer , physics
Abstract A modified injection molding machine with a compression mechanism, and a mold with a movable wall and shut‐off mechanism, were used to investigate the effects of processing parameters on the quality of injection‐compression‐molded polystyrene disks. The compression start‐up time, compression force, melt temperature, and part thickness were selected processing parameters. The disk moldings were evaluated based on dimensional accuracy and birefringence. It is found that the compression start‐up time affects packing time, and thus greatly affects the residual orientation. If the transition from packing to compression could start before peak cavity pressure, disks with low residual orientation could be obtained. High compression force improves part quality and reduces thickness. Since both compression‐induced reduction and cooling‐induced shrinkage are involved, the effects of temperature and thickness are not as straightforward as the trends in conventional injection molding.