Master of Engineering Science
Chemical and Biochemical Engineering
Dr. Paul Charpentier
Ontario greenhouse operations offer the ability to provide safe, local produce year-round. However, energy consumption associated with this service, as well as limited light intensity during winter months, is a significant problem. For this reason quantum dot (QD) nanoparticles and silica aerogel (SA) granules were investigated as potential filler materials for the enhancement of the optical and thermal properties of poly (ethylene-vinyl acetate) (EVA), a common greenhouse plastic, for the concurrent goals of increasing biomass production and reducing energy consumption in greenhouses.
The QDs, synthesized by colloidal chemistry using a single-molecular precursor method, along with commercial SA particles were integrated into EVA films by melt mixing the particles with the plastic in a mini-compounder. The resulting blends were extruded and pressed into thin films using a Universal Film Maker and a Carver hydraulic press. The experimental films were aged in an accelerated artificial weathering chamber to examine the effects of prolonged exposure to sunlight, heat and moisture. The new and aged films were characterized in terms of their optical, thermal, and material properties and the results were compared to commercial greenhouse films.
The films produced using QD nanoparticles displayed improved optical performance with decreased light transmission in the UV range, and increased transmission in the visible region. The SA films showed improved infrared retention above the performance of the commercial thermic plastics without compromising visible light transmission. However, increasing the SA concentration did not improve thermal conductivity, attributed to the EVA polymer infiltrating the pores of the aerogel. The experimental films were found to experience more severe chemical and physical aging in comparison to commercial films, however, the QDs incorporated in the experimental films provided some protection from oxidation, and the SAs slowed the progression of degradation effects.
Allan, Jenna M., "Light and Heat Selective Polymer Nanocomposite Films for Sustainable Greenhouses" (2012). University of Western Ontario - Electronic Thesis and Dissertation Repository. Paper 945.