טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentZoldan Janet
SubjectAnisotropy in the Structure and Properties of PP/Ny/CB
Blends Processed below the Melting of Ny
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Emeritus Siegmann Arnon (Deceased)


Abstract

The focus of the present research is the in-situ fibrillation of a dispersed phase during processing of binary and ternary immiscible polymer blends, resulting in oriented fibrils and electrically anisotropic systems. This structured morphology is achieved by compounding and processing just below the melting temperature of the dispersed phase, yet, above the melting temperature of the matrix.


Binary [PP/Ny] and ternary carbon black (CB) containing blends were characterized using scanning electron microscopy (SEM), high resolution scanning electron microscopy (HRSEM), differential scanning calorimeter (DSC), X-ray diffraction (XRD), tensile mechanical behavior and dielectric/electrical properties to study their process-structure-property relationships.


In both binary and ternary blends, the Ny fibrillation process caused the formation of an additional higher crystalline order melting peak and molecular orientation of the Ny (002) planes, enhancing the strength and modulus of the 260°C processed blends (just below the Ny Tm). In CB containing blends, Ny fibrils were attained only upon changing the processing sequence, i.e., adding Ny at the injection stage. These Ny fibrils were oriented in the flow direction, while maintaining phase continuity, and CB particles were located on their surface, leading to dielectric and electrical anisotropy. This was further confirmed by the Cole-Cole plots, which for the first time were found to fit numerical prediction of the “resistor-capacitor” (RC) Model.


The structured anisotropy in binary and ternary blends, attained by processing below the dispersed phase Tm, was directly correlated with the mechanical, electrical, and dielectric properties of the blends. Moreover, the dynamic electrical behavior was found a powerful tool for studying the CB dispersion mode in the polymer blends.