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Application of the rheology of monodisperse and polydisperse polystyrenes to the analysis of injection molding behavior
Author(s) -
Hagan R. S.,
Thomas D. P.,
Schlich W. R.
Publication year - 1966
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.760060416
Subject(s) - materials science , rheology , rheometer , shear rate , composite material , dispersity , molding (decorative) , mold , capillary action , viscosity , rheometry , melt flow index , polymer chemistry , polymer , copolymer
Monodisperse and polydisperse polystyrenes of equal weight average molecular weight ( M w ) are evaluated for melt flow behavior in an Instron capillary rheometer and for injection molding behavior in a 12 ounce in‐line reciprocationg screw injection molding machine. The influence of molecular weight distribution on the shape of the flow curves is deconstrated over a wide range of shear rate and temperature. The influence is also reflected in injection molding behavior as defined by pressure to fill or flash the mold at a given melt temperature. Studies of capillary rheometer data for correlation with injection moling beghavior indicate poor agreement when low shear rate viscosity data are used. Good agrement is foun using high shear rate viscosity data in the range 10 3 to 10 4 sec −1 Striking crossover points on melt rheology and injection colding area diagram curvs are found with the monodisperse and polydisperse polystyrenes of the same M These crossovers shift with melt temperature and make possible the determination of a “controlling shear rate” for the injection molding process. This is found to be 3500 sec −1 for short shot and 6200 sec −1 for flash with the ASTM test specimen mold used in this study.