(A) study on polymer blend/carbon nanotube composites fabricated by melt compounding

Abstract

In this research, polymer blend/carbon nanotube composites fabricated by melt compounding has been studied. The main objective of the thesis is to prepare conductive polyamide 6,6/poly(p-phenylene ether/multi-walled carbon nanotube (PA66/PPE/MWCNT) composites with the minimal amount of MWCNT loading, aiming for $10^{-6}$ S/cm of electrical conductivity. In chapter 2, morphological characteristics and electrical conductivities of PA66/PPE/MWCNT ternary nanocomposites were investigated. The MWCNTs was modified by a $^{60}Co$ gamma ray (γ-ray) irradiation under a dry condition and $O_2$ atmosphere, which introduces oxygen-containing functional groups on surfaces of the MWCNTs in order to provide better compatibility with hydrophilic PA66 phase. It was observed that the MWCNTs are selectively located in continuous PA66 matrix, whereas PPE domains are almost free from the MWCNTs. Since the PA66 consists a continuous phase and the MWCNTs are selectively located in the PA66 phase, electrical conductivities of PA66/PPE/MWCNT ternary composites are higher than those of PA66/MWCNT binary composites at same MWCNT content. Raising processing temperature and mixing time were observed to be effective to improve electrical conductivities by enhancement of MWCNT dispersion. The enhancement by changing processing condition is comparable to that by γ-ray irradiation, as far as PA66/PPE/MWCNT ternary composites containing 1 wt. % of MWCNT are concerned. However, a few reports have insisted that high temperature and long process time may cause thermal degradation, leading to decreases in mechanical properties. Thus, it is concluded that γ-ray irradiation on MWCNTs is a better way to enhance the dispersion of MWCNTs, since there is no risk of thermal degradation and deterioration of mechanical properties of the polymeric components.