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

Smuga, Jonathan R (2012) Conductively filled Poly(methyl methacrylate) composites; manufacture and testing processes for EMI shielding effectiveness. PhD thesis, Edinburgh Napier University.

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    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.

    Item Type: Thesis (PhD)
    Additional Information: I would initially like to thank Silberline for all their contributions throughout this research. Additional thanks to Microsphere Technologies for the sample materials provided
    Uncontrolled Keywords: Electromagnetic interference (EMI); shielding; conductively filled poly(methyl methacrylate) (PMMA) composites;
    University Divisions/Research Centres: Faculty of Engineering, Computing and Creative Industries > School of Engineering and the Built Environment
    Dewey Decimal Subjects: 600 Technology > 620 Engineering > 621 Electronic & mechanical engineering > 621.3 Electrical & electronic engineering > 621.34 Electromagnetic engineering
    Library of Congress Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
    Item ID: 5426
    Depositing User: Users 786 not found.
    Date Deposited: 15 Jun 2012 13:23
    Last Modified: 15 Jun 2012 13:23

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