Browsing by Author "Bishop, Peter Andrew"

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    Design and development of a modified spouted bed coater for the micro-encapsulation of powders : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Chemical Technology, Massey University
    (Massey University, 2003) Bishop, Peter Andrew
    A modified spouted bed coater was designed and constructed for the micro-encapsulation of solid particles. The coating of small particles with a polymer film can alter physical factors such as taste and release rate. These properties are particularly important in the field of pharmacology as the nature of the coating can be changed to prolong or target drug release based on physiological conditions such as pH and time. The spouted bed coater was modified to induce gas and particle recirculation through a draft tube containing a venturi to increase droplet and particle mixing, while a high velocity gas jet and large diameter draft tube promotes the recirculation of gas and solid within the apparatus. The effectiveness of the design was tested in terms of gas and solid mass flows through the draft tube using a venturi within the draft tube and an induction detector to measure the mass flow. To determine the effectiveness of the coater design in terms of coalescence and the influence of operational variables, a factorial experiment was conducted. The result of this experiment showed that the coalescence of particles was dominated by the relative humidity in the apparatus which was unable to be directly related to the operational variables. The capacity to micro-encapsulate particles was demonstrated by coating fine table salt with an acrylic polymer Eudragit NE 40D in combination with bentonite clay as a free flow agent or glident. The results of this trial showed the distribution of polymer/clay and the reduction in dissolution rate as a function of particle size.
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    Polymer coated controlled release agrichemicals as mitigation tools in pastoral farming : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2010) Bishop, Peter Andrew
    Controlled release coating technology and nitrification inhibitors offer potential mitigation options, for the reduction of pastoral nitrate leaching. Previous published research on this topic was reviewed indicating two potential areas of new research and development around two main hypotheses: • That polymer coated urea can allow high urea N applications in winter reducing application costs, nitrate leaching, herbage N content and urine N return to pasture. • That polymer coated nitrification inhibitor dicyandiamide (DCD) can increase the longevity of DCD in soil and effectively inhibit nitrification of dairy urine affected soils. To facilitate this research a range of coated urea and nitrification inhibitor dicyandiamide (DCD) products were produced using low cost, reactive layer, polyurethane (RLP) and were assessed in laboratory and field studies. The mechanism of urea release from modified RLP coated urea was investigated, leading to the development of a comprehensive model of release, based on the porous water repellent nature of the RLP coating. The “hydraulic convection” model was validated using water extraction and under field conditions for modified RLP coated urea. In, field trials (June-Nov 2007) using Italian ryegrass, a single application of 150 kgN ha-1 of palmitic acid modified RLP coated urea (5UCU) reduced winter nitrate leaching by 7 kgN ha-1 compared to uncoated urea and reduced peak herbage N levels over this period (150 days). Using an empirical N partitioning model for grazing cows, the reduction in herbage N was predicted to reduce urine N return by 5 to 10 kgN ha-1 over the 150 day trial. The effectiveness of laboratory prepared controlled release nitrification inhibitor dicyandiamide (PDCD) was tested as a surface application in repacked core studies on two soils contrasting in organic matter content and anion sorption capacity, Manawatu fine sandy silt and Dannevirke silt loam. The data from this trial was used to develop a model to explain DCD movement and degradation soils, which predicted that PDCD can potentially increase DCD longevity by 120 days at 20 oC over uncoated DCD.