Aspects of multi-walled carbon nanotubes in commercially viable, static dissipative aerospace coatings.

摘要

This thesis reports the development of a commercially viable, static dissipative,aerospace matt black polyurethane coating. A sheet resistance of 10 k/sq wasachieved with a loading level of 1.0 wt. % MWNTs, with electrical percolation atapproximately 0.3 wt. %.The characterisation of MWNTs available in commercially quantities above 1 kgis presented with key differences in agglomerate structure identified by scanningelectron microscopy (SEM) related to the synthesis method and the catalyst andcatalyst support used as identified energy dispersive X-ray spectroscopy (EDX). Atightening of the MWNT agglomerates after post processing such as purification,functionalisation and shortening is shown by SEM and confirmed using gas adsorp-tion and pore size distributions (PSDs).A scalable dispersion method based on probe sonication used to create 500 ml batchdispersions of MWNTs in organic solvents currently used in the coatings industryusing commercial high molecular weight dispersants. The required loading level wasdetermined using a stability check and related back to the specific surface area (SSA)obtained using the Brunauer–Emmett–Teller (BET) method. Changes in rheologyof the dispersions during sonication are related to the dispersion process using SEM.The compatibility of the MWNT dispersions when mixed with a commercial coatingresin are presented, and the onset of thixotropic behaviour, used to identify therheological percolation loading level.Standard coating tests confirmed the dry film properties of the coating are not ad-versely affected by the inclusion of the MWNT dispersions. It is shown that MWNTflocculation formed during mixing is broken during spray application but that floccu-lation also occurs during coating curing; un-pigmented systems being more severelyaffected than pigmented systems and higher curing temperatures and shorter timesbetween application and curing limiting the increase in sheet resistance.