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Morphology and mechanical properties of impact modified polypropylene blends
Author(s) -
Tortorella Nathan,
Beatty Charles L.
Publication year - 2008
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.21089
Subject(s) - materials science , polypropylene , izod impact strength test , melt flow index , composite material , reactive extrusion , miscibility , tacticity , elastomer , polymer , acrylate , polymer blend , copolymer , polymerization , ultimate tensile strength
Isotactic polypropylene (PP) has been reactively blended with various grades of an ethylene–octene copolymer (EOC) in a twin‐screw extruder. Free radical polymerization of styrene and a multifunctional acrylate during melt extrusion has resulted in an enhancement of mechanical properties over the binary blend. The reactive blend exhibits a notched Izod impact strength over 12 times that of pure polypropylene and greater than double the performance of the binary blend. Electron microscopy shows that by grafting onto the polymers, elastomer particle size and interparticle distance decrease, while particle shape becomes less spherical. The acrylate is crucial to achieve superior performance, as infrared spectra correlate an increase in graft yield to improvements in stress–strain behavior and impact strength. In addition, melt flow index (MFI) and melt strength data indicate a reduction in unwanted side reactions of polypropylene and the presence of long‐chain branching. Dynamic‐mechanical analysis reveals that the reaction promotes miscibility between polypropylene and the EOC and reduces molecular mobility at their glass‐transition temperatures. Mechanical properties, graft yield, and MFI are shown to be highly dependent upon the elastomer's concentration, density, and molecular weight, initiator and monomer concentration, as well as processing temperature. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers