| Flavors and Fragrances related to our lives closely, but they have many problems in use and storage, such as short release time, low washing resistance, perishable and so on. Microencapsulation can solve these problems effectively. Fragrance microcapsules, with a methanol-modified melamine-formaldehyde(MMF) resin shell, were fabricated with an in-situ polymerization method in the presence of styrene-maleic anhydride copolymer(SMA). The mechanism, particle size control method and properties of microcapsules were studied.1. The FT-IR results and TG-DTG tests showed that the essence oil was encapsulated by MMF resin. The fabrication process was observed by reflection and transmission optical microscope, and the encapsulation mechanism was studied according to the observation results. It was found that the adsorption of MMF resin to SMA and the poly-condensation reaction kinetics played key roles in the microencapsulation process. Additionally, the process of microencapsulation contains two re-formations, which were caused by the p H effect in the hydrolysis of SMA and the re-dispersion of droplets in curing process.2. According to the proposed encapsulation mechanism, a series of microcapsules with different size and distribution were prepared by the adjustment of reaction parameters. The key factors of microcapsules size control was studied by using microscopic analysis and laser particle sizer. Experiments show that the amount of SMA, stirring speed, p H and p H adjusting stage has a significant effect on the microcapsule size and distribution. During the large-scale preparation, it is found that the impact of fluid flow also will be enlarged. In order to improve the heat transfer and dispersion effects, a new type orifice paddle was used as stirring equipment. The particle size distribution of microcapsules was significantly narrowed, and it is can gained the narrower size distribution while use the paddle with more number of aperture and smaller diameter.3. The thermal stability of fragrance microcapsules was researched by using TG tests and micro melting point apparatus. The results indicated that its thermal stability was improved significantly by the microencapsulation and the larger size microcapsules easily broken up during the heating process, while a smaller diameter microcapsules have better resistance of thermal rupture, which the most of core material in them cannot release until the wall material decomposition.4. Fragrance microcapsules release properties was studied in 2403 hours by using the weigh and calculation method. The core material release data were analyzed by curve fitting with a power function. Further the data after 555 hours was fitted to obtain the prediction curve of fragrance microcapsules sustained release rate. Finally, the particle sizes of microcapsules were introduced in the resulting equation, and the empirical equations of release rate were obtained. Based on them, we can do the approximate prediction of any size of fragrance microcapsules sustained release rate.5. Using the prepared microcapsules with different particle size in cotton fabric finishing to studied the key factors of finishing by microcapsules. With the method of microscopic image analysis and friction sniffing, it is found that microcapsules within a certain range, the larger the particle size, the better breakability. When microcapsules particle size in the range of 15~30μm, it can gain the highest finishing efficiency, the resultant finished fabric having best rub release performance. |
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