Preparation And Performance Characterization Of Essential Oil Microcapsule

Microcapsules containing oil-based fragrances are commonly employed in the field of house-hold products such as cosmetics,detergent and textile.However,various fragrance oils were encapsulated via specific microencapsulation technologies becasue of different frangrance oils with different chemical compositions.In this work,a general and versatile strategy to prepare melamine-formaldehyde(MF)microcapsules encapsulating clove oil with chain-end lively double bond by combining solvent evaporation and in situ polymerization was proposed.Oil-based fragrance droplets were pre-encapsulated by an inner thin polyacrylate shell membrane,as an intermediate bridging layer to prepare fragrance oils microcapsules.The amount and composition of the intermediate polyacrylate bridging layer,the feeding sequence of acid catalyst,the feed batch and amount of MF precondensate,stirring speed and the amount of protective colloid were systematically studied.The main conclusions as follow:1.MF-clove oil microcapsules were prepared successfully by combining solvent evaporation and in situ polymerization.Clove oil droplets were pre-encapsulated by an inner thin polyacrylate shell membrane,followed by in situ polymerization of MF precondensate as an outer shell.In addition,it was demonstrated sunflower oil and hexyl salicylat could be encapsulated via this preparation method.2.The amount and the concentration of AA of the intermediate polyacrylate bridging layer were significant to the formation of MF microcapsule.The incomplete MF fragrance microcapsules were observed when the amount of polyacrylate was low.The number of active reaction sites were not enough on the droplet surface if the content of AA was scarce.However,smooth and sphere-shape MF fragrance microcapsules were prepared when increasing the weight and concentration of AA of polyacrylate which increased the active reaction sites and drived MF procondensate molecules to gather the surface of pre-encapsulated droplets followed by polymerization of MF to form microcapsule shell.3.The surface morphology with various wrinkles of MF microcapsules can be effectively tuned via changing the feeding sequence of acid catalyst and the feed batch of MF precondensate.Fine particles clustered microcapsules were synthesized when glacial acetic acid was added to the MF procondensate,and then added above mixture to the reaction system.Rough microcapsules were synthesized when glacial acetic acid and MF procondensate were added to the reaction system simultaneously.And smooth microcapsules were prepared when MF procondensate was added and then added glacial acetic acid.Moreover,MF fragrance microcapsules with various wrinkle were synthesized via changing the feed batch of MF precondensate to adjust the compatibility between MF resin and precondensate because MF precondensate had various crosslinking degree in different stages.Furthermore,internal stress generating in the polymerization process would be died down by changing the feed batch of MF precondensate.4.Stirring speed and polyvinyl alcohol dosage played a key role in particle size control of the MF fragrance microcapsules.The microcapsule with smaller size and narrow distribution was obtained when increased the stirring rate and polyvinyl alcohol dosage.5.There are micropores in the shell of MF fragrance microcapsules.Fragrance oil was leaked through these micropores.The controlled release behavior of fragrance oil could be controlled by changing the surface texture of microcapsules.