Browsing by Author "Jayaweera, N."

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    Preparation and Characterization of a Mosquito Repellent Paint
    (Uva Wellassa University of Sri Lanka, 2016) Arunraj, A.; Jayaweera, N.; Jayasuriya, C.K.
    Paints are used to decorate, protect and extend the life of natural and synthetic materials. The current research focuses on a different aspect on which paint can be utilized. The objective of this study was to develop a mosquito-repelling paint while maintaining the desired paint properties. In this regard, neem oil, one of the known mosquito repellents was used as an additive in emulsion paint formulation. A series ofpaint samples were made according to the interior paint formulation by varying the amount of neem oil. The reference sample was prepared without adding neem oil. In addition, properties were also compared with a commercial paint sample. For each 500 g of emulsion paint, neem oil was added in amounts to prepare samples with neem oil percentages 4 wt%, 8 wt% and 12 wt%. Various paint properties of thus prepared paint samples were investigated. The mosquito repellency of the paint samples were monitored by counting the mosquitoes flying on to the surfaces coated with the paint at 30-minute intervals for 4 hours. Neem oil added paint samples show improved mosquito repellency, however, it could be retained only for few days. This drawback could possibly be remedied by using a proper bonding agent to prevent volatility of the active ingredient. According to the results, opacity and glossiness of the paints with neem oil are lower compared to those of the industrial paint sample. Some improvements in these properties could possibly be achieved by maintaining pH in the neem oil added samples close to that of the industrial sample. According to the results, water resistance is significantly reduced upon adding neem oil compared to the industrial paint sample. Further research must be carried out with a proper bonding agent to retain the desired paint properties as well as the mosquito repellency. Keywords: Mosquito-repelling paint, neem oil
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    Reducing Photocatalytic Degradation of Exterior Paint Prepared with TiO2
    (Uva Wellassa University of Sri Lanka, 2016) Dissanayake, S.D.M.A.S.S.; Jayaweera, N.; Jayasuriya, C.K.
    Titanium dioxide (Ti02) is the most widely used white pigment in the paint industry. TiO, is a photocatalyst under ultraviolet (UV) light. When it absorbs UV radiation, a UV photon which overcomes the energy gap between the valence and conduction bands of TiO, creates an electron-hole pair. The hole then reacts with water to produce hydroxyl radicals followed by a series of other reactions that produce more and more hydroxyl radicals which react with the organic matter to form water and carbon dioxide leading to the destruction of the polymeric binder of the paint film. This effect could be reduced by mixing the pigment with an inert oxide such as silica. The current research focuses on reducing photocatalytic effect of TiO2 and thereby increasing the durability of the paint. A series of emulsion paint samples were prepared according to an exterior paint formulation by varying the ratio Ti02:Si02. Formation of photocatalytic oxides were determined by measuring the absorbance using Orange II solution. Samples were exposed to UV radiation by applying them on small watch glasses as thin layers. The solution absorbance values on the samples were measured before and after exposure to UV radiation and recording absorbance at 60 min, 120 min and 240 min. The best sample with the lowest photocatalytic effect was used to determine paint properties. The lowest photocatalytic effect was observed for the sample containing 20% SiO2 and 80% of TiO2 and the paint properties were determined for that sample. Most of the properties are comparable with those of the industrial paint. However, viscosity and opacity are significantly reduced. It could be due to the undesired particle size of silica incorporated. Further investigations must be carried out to determine the optimum particle sizes which give the lowest photocatalytic effect with enhanced paint properties. Keywords: Photocatalytic Effect, Paint, Titania, Pigment