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Anisotropy in the electrical behavior of immiscible polypropylene/nylon/carbon black blends processed slightly below the melting temperature of the nylon
Author(s) -
Zoldan J.,
Siegmann A.,
Narkis M.
Publication year - 2006
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.20594
Subject(s) - materials science , polypropylene , carbon black , composite material , differential scanning calorimetry , scanning electron microscope , molding (decorative) , polymer blend , phase (matter) , polymer , polymer chemistry , copolymer , natural rubber , chemistry , physics , organic chemistry , thermodynamics
Carbon black (CB) containing polypropylene/nylon (PP/Ny) blends, processed slightly below the melting temperature ( T m ) of the dispersed Ny phase, leads to formation of fibrillar Ny phase and electrically anisotropic systems. CB containing PP/Ny blends were compounded (twin screw extruder) and processed (injection molding) slightly below the T m of dispersed Ny phase at different blending sequences. To establish structure–property relationships scanning electron microscopy, high resolution scanning electron microscopy, differential scanning calorimeter were used and electrical properties were also studied. Addition of CB to binary PP/Ny blends, processed below the Ny T m , altered the Ny fibrillation process forming an irregular continuous phase, containing the CB particles, rather than the fibrils formed in the PP/Ny blends. Yet, upon changing the processing sequence, i.e., compounding PP and CB and then adding Ny in the injection molding stage, Ny fibrils were attained, maintaining phase continuity, oriented in the flow direction and CB particles preferentially located on their surfaces. Blends exhibiting a fibrillar Ny network covered by CB particles exhibited electrical anisotropy. The Ny fibrils exhibited an additional higher crystalline melting peak and molecular orientation. The composites are conductive in the Ny fibril direction, while insulating in the perpendicular direction. Once the CB is located within both, the Ny and the PP matrix the electrical behavior is isotropic. POLYM. ENG. SCI., 46:1250–1262, 2006. © 2006 Society of Plastics Engineers