EMI properties of electroless nickel-coated mica in different polymer matrices

The objective of this research is to develop conductive plastics for the shielding of electromagnetic interference (EMI). In conducting polymer composite materials, conducting particles are incorporated in an insulating matrix. A well characterised grade of mica was used to prepare nickel-coated mica fillers. Work involved optimisation of different factors including the effects of agitation, temperature, pH, catalyst concentration and concentration of nickel solution. Systems with separate activator and sensitiser, and also with a single solution containing both activator and sensitiser were examined. A pH of 5 and reaction temperature of 88–90°C were found to be very effective for electroless nickel coating. After optimising the coating technique, the process was scaled up so that filler/polymer composites could be produced. To optimise the conductivity of filler the nickel coating needed to exceed a certain weight percentage, depending on the particle size of the mica. Pre-treated mica surfaces were analysed by laser induced mass analysis (LIMA). Coated samples were analysed using an Atomscan spectrometer with an inductively coupled plasma emission source for accurate determination of phosphorous content. [Continues.]