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Injection and compression molding of polystyrene/high‐density polyethylene blends—phase morphology and tensile behavior
Author(s) -
Bureau M. N.,
El Kadi H.,
Denault J.,
Dickson J. I.
Publication year - 1997
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.11680
Subject(s) - materials science , high density polyethylene , composite material , ultimate tensile strength , compatibilization , polystyrene , rheology , polymer blend , polyethylene , phase (matter) , compression molding , shear rate , coalescence (physics) , polymer , copolymer , mold , chemistry , organic chemistry , physics , astrobiology
Processing and compatibilization effects on the phase morphology and the tensile behavior of blends of polystyrene and high‐density polyethylene (PS/HDPE) were investigated. As predicted by theory, high shear rates encountered during extrusion blending led to efficient minor phase emulsification in immiscible PS/HDPE blends for which the viscosity ratio approaches unity. Consequently, the emulsifying effect of a styrene/ethylene‐butylene/styrene (SEBS) compatibilizer was found to be negligible. In the subsequent molding process, disintegration, shape relaxation and coarsening of the minor phase domains were found to be responsible for the morphological evolution. In the compression molding process, morphological observations showed that the rate of minor phase coarsening followed the predictions of the Ostwald ripening theory, in agreement with the rheological analysis. In the injection molding process, minor phase coarsening was attributed to shear coalescence. Tensile tests performed on compression molded and injection molded blends showed that the mechanical behavior of PS/HDPE blends depend strongly upon the matrix orientation as well as the dispersed phase morphology and orientation. In both postforming operations, compatibilization effects on the morphological stability and the tensile behavior of PS/HDPE blends were found to be dependent upon the composition and the rheological behavior of the blend. Evidence of adhesion between the PS and HDPE phases was observed in the presence of SEBS in HDPE‐rich blends.