EFFECT OF ASPECT RATIO OF MULTI-WALLED CARBON NANOTUBES ON ELECTRICAL, THERMAL AND MECHANICAL PROPERTIES OF COMPOSITES WITH POLYCARBONATE

摘要

The purpose of this work is to explore the question of how the aspect ratio of carbon nanotubes (CNTs) affects various properties in polycarbonate/CNT composites. Aspect ratios (prior to mixing) of multi-walled carbon nanotubes varied between 50-500. Tubes were mixed with polycarbonate in a conical twin-screw compounder and then compression molded into flat sheets. Differential scanning calorimetry, dynamic mechanical analysis and tensile properties were measured on the as-molded sheets. At low aspect ratios, the aspect ratio correlated to both the percolation threshold and the rubbery modulus in a simple linear fashion; however with a significant level of scatter. At high aspect ratios, the percolation threshold did not change with aspect ratio which was attributed to a higher relative amount of length reduction during processing above a certain length value leading to similar length after processing. Reducing the time of mixing or the rotation speed of the screws led to a lower percolation threshold attributed to less nanotube breakage.