Study of atmospheric pressure weakly ionized plasma as surface compatibilization technique for improved plastic composites loaded with cellulose based fillers
Lekobou, William Pimakouon
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Atmospheric pressure plasmas have gained considerable interest from researchers recently for their unique prospective of engineering surfaces with plasma without the need of vacuum systems. They offer the advantage of low energy consumption, minimal capital cost and their simplicity as compared to conventional low pressure plasmas make them easy to upscale from laboratory to industry size. The present dissertation summarizes results of our attempt at applying atmospheric pressure weakly ionized plasma (APWIP) to the engineering of plastic composites filled with cellulose based substrates. An APWIP reactor was designed and built based on a multipoint-to-grounded ring and screen configurations. The carrier gas was argon and acetylene serves as the precursor molecule. The APWIP reactors showed capability of depositing plasma polymerized coating rich in carbon on substrates positioned within the electrode gap as well as downstream of the plasma discharge into the afterglow region. Our findings show that films grow by forming islands which for prolonged deposition time grow into thin films showing nodules, aggregates of nodules and microspheres. They also show chemical structure similar to films deposited from hydrocarbons with other conventional plasma techniques. The plasma polymerized deposits were used on substrates to modify their surface properties. Results show the surface of wood veneer and wood flour can be finely tuned from hydrophilic to hydrophobic. It was achieved by altering the topography of the surfaces along with their chemical composition. The wettability of wood veneer was investigated with contact angle measurements on capacitive drops and the capillary effect was utilized to assess surface properties of wood flour exposed to the discharges.