Research Output

Conductively filled Poly(methyl methacrylate) composites; manufacture and testing processes for EMI shielding effectiveness.

  Electromagnetic interference (EMI) is an escalating concern in the modern electronic
climate. As such it has become a critical area to consider when designing and packaging
electronics. With the growing volume of electronic devices available and with processor
frequencies increasing, the electromagnetic environment is becoming ever more
congested. The need for adequate EMI shielding has become an essential consideration.
The desire for high performance combined with reductions in size, weight and
manufacturing cost suggests that polymers should be ideal materials for parts such as
electronic housings. Unfortunately polymers generally do not provide shielding from
electromagnetic waves.
The research detailed in this thesis investigates the manufacture and testing of
conductively filled poly(methyl methacrylate) (PMMA) composites. Samples of PMMA resin and various electrically conductive filler materials were manufactured. The processing methods, electrical properties and electromagnetic behaviour were all investigated. Composite polymer coatings were printed with a K-Control Coater and evaluated for surface resistivity and EMI shielding effectiveness. Samples were produced with a range of filler materials including nickel, carbon, copper/aluminium
and silver coated glass spheres. Shielding effectiveness values of approximately 70 dB
were obtained for coatings of PMMA filled with silver coated hollow glass microspheres.
Attempts were made to produce an alternaalternative filler material by electroless nickel
plating of expanded graphite powder. Successful plating was achieved using
conventional methods of surface sensitisation of the graphite. This however resulted in agglomerations of the powder and a loss of the desired physical properties. Alternative
thermal surface treatments proved to be unsuccessful in activating the graphite surface
with no nickel deposition occurring.
Furthermore, electroless nickel plating techniques were successfully utilised in the
development of an alternative manufacturing process for producing electrically
conductive PMMA composites which contained a reduced metallic content, in relation
to a more traditional production technique. Plaques were manufactured by compression
moulding of nickel plated PMMA granules. These were compared against samples
manufactured with nickel powder mixed in a Brabender Plasti-Corder. The electroless
plating method produced samples that outperformed the comparative method and were
shown to contain a reduced metallic content. Shielding effectiveness of the electroless
plated granule samples achieved approximately 34 dB compared to a maximum of only
2.5 dB for the Brabender compounded samples.
Outwith these areas of empirical testing a computer model was produced to simulate the
electromagnetic shielding behaviour of composite materials using Comsol Multiphysics.
This model appears to successfully simulate the waveguide testing apparatus. However
the theoretical conductivity values as calculated from effective media theory resulted in
disproportionate shielding effectiveness values obtained.
Further research into the electroless plated and compression moulded PMMA composites would be beneficial in order to fully optimise the process. Equally the theoretical model would require further investigating and validating before more accurate simulations could be achieved.

  • Type:

    Thesis

  • Date:

    15 June 2012

  • Publication Status:

    Unpublished

  • Library of Congress:

    TK Electrical engineering. Electronics Nuclear engineering

  • Dewey Decimal Classification:

    621.34 Electromagnetic engineering

Citation

Smuga, J. R. Conductively filled Poly(methyl methacrylate) composites; manufacture and testing processes for EMI shielding effectiveness. (Thesis). Edinburgh Napier University. Retrieved from http://researchrepository.napier.ac.uk/id/eprint/5426

Keywords

Electromagnetic interference (EMI); shielding; conductively filled poly(methyl methacrylate) (PMMA) composites;

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