| A variety of infectious diseases caused by mosquito bites have done great harm tohuman health and the development of a variety of insect repellents is critical. The mainresearch direction is the development of nontoxic and environment friendly natural insectrepellent. In this study microspheres were prepared using citronella oil as a natural insectrepellent that were coated by natural polymers and synthetic polymers, then preparedmicrospheres were loaded onto the fabric so that citronella oil was steadily sustainablereleased and best repellent effect was obtained. The main research contents and methodsincluded as follow.(1) Gelatin/citronella oil microspheres were prepared by single coacervation. Theoptimum process parameters were determined by using orthogonal experiment when theparticle size of microspheres was used as evaluation index. Yields, encapsulationefficiency, oil load, water ratio, particle size and release rate of microspheres wasdiscussed.(2) Gelatin/gum arabic citronella oil microspheres were prepared by complexcoacervation. Micromorphology of gelatin/gum arabic citronella oil microspheres wascharacterized, experimental parameters such as yields, encapsulation efficiency, oil load,water ratio, particle size and release rate of microspheres were analyzed, and controlledrelease of gelatin/gum arabic citronella oil microspheres in air was studied.(3) Polyurethane citronella oil microspheres were prepared by using isophoronediisocyanate (IPDI) and polyethylene glycol (PEG) and carboxymethyl-cellulose sodium(Na-CMC) dimethylolpropionic acid (DMPA) as main materials and characterized.Release of polyurethane citronella oil microspheres under different pH was studied.(4) Inorganic mineral particles modified polypropylene fibers prepared by meltspinning process were interwoven with colored cotton, then polypropylene fiber coveredcolored cotton textile was prepared. Gelatin/arabic citronella oil microspheres prepared bycomplex coacervation were loaded to fabric by after-fininshing method. The releasing properties of loaded microspheres fabric were studied.The morphology of citronella oil microspheres were observed by the opticalmicroscope. Granularity distributions of microspheres were analyzed by laser particle sizeanalyzer. Polyurethane citronella oil microspheres were characterized by FTIR andDSC-TG. Morphologies of polyurethane microspheres, modified polypropylene and fabricsample were observed by SEM. The crystallization of modified polypropylene fiber wasstudied by XRD. The releasing property of microspheres was determined by Uvspectrometer.The results showed that:(1) Optimal scheme of preparing single coacervation gelatincitronella oil microspheres was when stirring speed was800rpm, the best mass ratio ofcitronella oil to gelatin was1:1, dose of crosslinking agent was10mL, and pH was9,single coacervation gelatin citronella oil microspheres with narrow diameter distribution,good spherical structure and release rate were prepared. When the concentration of gelatinwas2%, yield, encapsulation efficiency, oil load, water ratio, particle size and release ratereached a higher value. The two most important factors for microsphere diameter relatedto stirring rate and S which was core-shell ratio. The release rate existed obvious variationunder different core-shell ratio and stirring rate. Sustainable release time of simplecoacervation gelatin citronella oil microspheres was more than4h and its final release timewas above10h.(2) The particle size of multi-core structural microspheres was big andspherical structure was poor using gelatin and sodium carboxymethyl cellulose as wallmaterial whereas multi-core complex coacervation microspheres had good sphericalstructure using gelatin and gum arabic as wall material. The optimum technologicalconditions for preparing complex coacervation microspheres were obtained whencore-shell ratio was2:1, wall material concentration was20%, pH was4, and stirring ratewas800rpm. The kinetic equation of complex coacervation microspheres release processfitted first order linear relation. Sustainable release time of complex coacervation gelatincitronella oil microspheres was more than8h and its final release time was above20h.(3)The optimum conditions for preparing citronella oil polyurethane microspheres wereobtained when the content of DMPA was5wt%, the molar ratio of isocyanate and hydroxyl was3, the quality ratio of Na-CMC and PEG was10%, the reaction temperaturewas80℃, and the reaction time was3h. Sustainable release time of complex coacervationgelatin citronella oil microspheres was more than4h, its final release time was above20hand ultimately release rate was over80%.(4) Inorganic mineral particles modifiedpolypropylene fibers were successfully prepared by melt spinning process. When theadditive content is5%, the best performance of fiber and yarn was achieved. Complexcoacervation citronella oil microspheres with a longer sustainable release time was loadedinto PP fiber covered color cotton textile and its sustained release time was over8h, andultimately release time was above20h. |
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