Papers by Author: Jian Hong Zhao

Abstract: Multi-walled carbon nanotubes (MWCNTs) were functionalized with a carboxyl group (-COOH) to improve their dispersion in a nylon6 (PA6) matrix, a liquid crystal polymer (LCP) and their blend. This functionalized MWCNTs also achieved better interfacial adhesions with both polymer matrices and with both phases in the blend. The dispersion of MWCNT-COOH in the polymer matrices and their interfacial interactions with polymer molecules were found to be the most important factors affecting the properties of composites. Moreover, studies on morphological, rheological, and mechanical properties confirmed that a better miscibility between PA6 and LCP had been constituted in the presence of MWCNT-COOH. Therefore, it is observed that the functionalized MWCNTs not only played the traditional role as reinforcing fillers in the polymer matrices, but also performed a novel role as compatibilizers for their blend.

Abstract: Composites of polypropylene (PP) and multi-walled carbon nanotubes (MWCNTs) were prepared by a micro melt mixing process. The molecular weight of PP was varied from 190,000 to 340,000 to examine its effects on the electrical conductivity. It has been discovered that a significant enhancement of electrical conductivity could be achieved by a thermal post annealing process above the melting temperature of PP. Factors such as annealing time, temperature, viscosity of PP, and content of MWCNTs all affected the enhancement of electrical conductivity. Re-aggregation of MWCNTs and the subsequent formation of MWCNT networks during annealing are considered to be the main reasons for the quick enhancement of electrical conductivity. The observed effect of molecular weight of PP on the enhancement of electrical conductivity suggested that the enhancement process could be controlled by diffusion of MWCNTs.

Abstract: There are increasing demands for polymer based microfluidic devices as polymer devices can be mass produced using the injection molding process for disposable analytical applications. However, fabrication of precision injection molds with micro features down to tens of micro meters is a challenging task. The most efficient manufacturing method for this type of high precision micro mold is the tool-based micro machining. In this paper, studies have been conducted to develop metal injection mould manufacturing technologies for polymer microfluidic device fabrication. An injection mould with a micro feature of 29m wall thickness, 20m height and 9.8mm length has been successfully achieved on brass with very precise dimensional accuracy and surface quality for molding process of polymer microfluidic devices. Polymer microfluidic chips with micro channels of 30m width have been successfully produced using the machined metal injection mould.