Preparation And Performance Characterization Of Melamine Formaldehyde Perfume Microcapsules

Perfume-filled microcapsules have a wide application in personal-care and household products.Melamine formaldehyde(MF)resin,as a kind of shell materials,has been caught attention by many researchers since its low price,the excellent performances and the convenience on the preparation process.However,the study on the preparation of MF prepolymer has been seldom mentioned,especially the influence of MF prepolymer with different properties on the preparation of microcapsules.Meanwhile,the mechanismto form a MF resin shell on the surface of the core material is not clear enough.Therefore,in this work,perfume-filled microcapsules were prepared by using in-situ polymerization with hexyl salicylate as the core material,MF resin as the wall material,and poly(acrylamide-co-acrylic acid)-partial sodium salt(P(AM-co-AA)-p S)as the protective colloid.The influence of the experimental conditions on the molecule weight of the prepared MF prepolymer,the preparation mechanism to prepare perfume-filled microcapsules and the experimental conditionson the preparion of perfume-filled microcapsules were studied.The main conclusions are as follows:1)Methanol etherification increased the stability of the MF prepolymer and it has been stabe for more than 2 months.Moreover,the molecule weight of the MF prepolymer can be well controlled by adjusting the acidification time,the acidification p H,and the neutralization p H during distillation.2)Melamine formaldehyde-hexyl salicylate microcapsules were prepared successfully by in-situ polymerization.The microcapsules were well in spherical shape with smooth surface without defects;and they were in typical core-shell structures.Fourier transform infrared spectrometry(FTIR)and ultraviolet spectrum(UV)analysis indicated that the core material has been successfully encapsulated by the MF resin;thermogravimetry(TG)analysis showed that the prepared MF perfume-filled microspheres had good thermal stability up to 150?,and the loading rate was about 55 wt%.3)The study showed that the molecular weight of MF prepolymer in the preparation of microcapsules was crucial for the formation of MF microcapsule shell.With the promotion of the electrostatic attraction of protective colloid,the MF prepolymer molecules grown to appropriate molecular weights in the acidification polycondensation stage,and then they were migrated to the surface of the oil droplets and further cross-linked to form MF microcapsules shell.4)By adjusting the amount of protective colloid P(AM-co-AA)-p S and the stirring speed,the particle size and particle size distribution of the microcapsules can be effectively controlled.By increasing the agitation rate and the amount of P(AM-coAA)-p S,the average particle size of microcapsules and the width of the particle size distribution reduced.However,the molecular weight of P(AM-co-AA)-p S had no obvious effect on the preparation of microcapsules.The ratio of shell-core and the ratio of oil-water phases in the preparation of microcapsules could effectively adjust the shell thickness and the spherical integrity of the microcapsules.When the weight ratio of shell-core and the oil-water phases were within the range of 1.5~1.75 and 0.1~0.15 respectively,microcapsules maintained good core-shell structures in dry condition.When the concentration of the shell materials was low,the amount of MF needed for shell forming was not enough to encapsulate the core oil droplets,and the structural defects were observed.When the concentration was high,the extra MF prepolymer may react in water phase and then it may increase the number of MF fragments to from MF residue,which will affect the product performance.5)By investigating the effects of the feeding modes on the preparation of microcapsules,advancing the time point for adding MF prepolymers,reducing the number of coating times,and using MF prepolymers with the low molecular weight increased the thickness of the microcapsules and less microcapsules ruptures were observed.Due to the residue of the MF particles and the complexity of the preparion process,it is not preferable to use this process to adjust the wall thickness of the microcapsules in industrial production.However,it may be useful for suface modification on microcapsules in the future work.