Investigation of polyaniline and carbon nanotubes as melt processable electrically conducting dopants for polyethylene

The goal of the research described in this thesis was to create composites which have consistent values of electrical conductivity that can be suitably tailored depending on production method to yield a range of low cost flexible 'electronic' materials. Blends of linear low density polyethylene (LLDPE) with 8, 10 and 12 wt.% polyaniline (PANI) and similar formulations with varying concentrations of carbon nanotubes (CNTs) were prepared using melt blending. The morphology of the blends and dispersion of the CNTs were examined by a combination of X-ray diffraction, scanning electron microscopy and transmission electron microscopy which showed that some nanotubes were well dispersed but there was evidence of agglomeration at higher loadings. The. ultimate tensile strength (UTS) of the composites tended to decrease with increased PANI content but modulus remained constant. 3-5 wt.% CNTs improved the UTS of LLDPEIPANI composites but higher CNT :oading decreased strength and elongation at break. Volume resistivity measurements were taken from sheet samples, revealing that LLDPEIPANI composites had attained a percolation threshold, with a drop in resistivity from 1018 to 108 a.cm for 12 wt.% PANI. Resistivity values for LLDPE composites containing CNT and PANI/CNT were influenced by film thickness. Electrochemical impedance spectroscopy examined effects occurring at the boundary between composite surfaces and an electrolyte solution. Using this technique, MWCNTs were seen to reduce the resistance of the composite. Solid state impedance spectroscopy was used to characterise the electrical behaviour of the bulk material and revealed that no LLDPEIMWCNT composites were percolated for 500 Jlm thick specimens. Furthermore, it revealed that MWCNTs eliminated the current carrying capacity ofPANI in LLDPE/PANIIMWCNT composites. Supplied by The British Library - 'The world's knowledge'EThOS - Electronic Theses Online ServiceGBUnited Kingdo