Carbon nanotube/MF composites

Licentiate thesis, 2005

A new generation of composites, frequently referred to as nanocomposites, are making research and engineering impact worldwide. Particularly, the incorporation of carbon nanotubes (CNT) into polymers is attractive, due to the generally good processability of polymers and the unprecedented properties of nanotubes. Stiffness and strength enhancement, favourable processing characteristics as well as increased functionality are being imparted to a growing range of polymers, by filling them with carbon nanotubes. Some of the so-far studies have focused on coating polymers filled with CNT. However, melamine-formaldehyde (MF), an important coating polymer, has not been studied as a matrix for CNT composites. In this work, MF filled with single-wall (SWNT) and filled with multi-wall nanotubes (MWNT), is studied. Low amounts of nanotubes are used. Alpha-cellulose is added to MF in order to improve the processing conditions, and to enhance the performance in the solid state. Thus a ternary CNT/cellulose/MF composite is prepared and analysed MWNT are carboxilized, and X-ray photoelectron spectroscopy (XPS) is used to characterise the carboxilation. Next, the functionalised nanotubes are dispersed in MF aqueous solution. An anionic sodium dodecyl sulphate (SDS) surfactant is used to assist the dispersion. Viscosity of the dispersion is measured. A manufacturing technique developed by us earlier for carbonaceous micro fillers in MF is adapted. A dispersion is deposited on alpha-cellulose papers, impregnated papers are stacked and hot-pressed to form a solid nanocomposite. Electron and light microscopy is used to observe the composite solid state morphology and dispersion in the liquid-phase. Solid state mechanical properties are measured and analysed.