Preparation Technology Investigation Of In-situ Polymerized PUF Microcapsules

Urea-formaldehyde microcapsules can be applied to many fields such as energy storage,self-repair,self-lubrication and self-cleaning,due to simple synthesis process,low raw materials,and their excellent mechanical properties,which makes Urea-formaldehyde microcapsules become research hotspot.In this paper,urea and formaldehyde were used as reaction monomers,and two kinds of microcapsules coated with epoxy resin(E-51)/SM-80 and epoxy small molecule(SM-80)were prepared by in-situ polymerization.It is intended to be applied to epoxy anti-corrosion coatings to provide self-repairing ability of the cured coating,prolong the service life of the coating and achieve long-lasting corrosion protection.By means of optical microscopy(OM),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),thermogravimetric analyzer(TGA),the effects of process parameters such as emulsifier type and dosage,emulsification speed,initial pH value,prepolymer concentration and heating rate on the morphology,particle size and coverage of microcapsules were studied systematically.It mainly includes the following contents:Microcapsules prepared by using SM-80 as the core material and urea-formaldehyde resin as the wall material.The effects of wall concentration,initial pH value and heating rate on the morphology of microcapsules during the microencapsulation of urea-formaldehyde resin were studied.Tween-80 is used as the emulsifier,the prepared SM-80 microcapsule product has a smooth surface and uniform particle size distribution and high coverage.The stirring speed was from 200 r/min to 500 r/min,and the average particle diameter and the coating ratio of the microcapsules were not affected.When the core-wall ratio is 0.6:1,the surface morphology of the microcapsule product is smooth and the coverage rate is the highest.The main order of influence on the core content of urea-formaldehyde microcapsules was core-wall ratio>heating rate>initial pH value.Considering the comprehensive factors,the preparation conditions are optimized,the initial pH value is from 4 to 5,the wall material concentration is 8.3 wt%,and the heating rate is 1?/min,SM-80 urea-formaldehyde microcapsules with smooth surface,uniform particle size distribution,particle size of about 5 ?m and 68%core content were successfully prepared.The microcapsules with E-51/SM-80 as the core material and urea-formaldehyde resin as the wall material were prepared.The effects of emulsifier,emulsifier dosage and emulsification speed on microcapsules were studied.Microcapsule products can be obtained using the nonionic surfactant OP-10 and tween-80 as emulsifiers.The dosage of Tween-80 is 3wt%,and the microcapsule product can be obtained.When the amount of tween-80 is from 1wt%to 3wt%,the particle size of the microcapsules is significantly reduced;from 3 wt%to 8 wt%,the particle size is slightly reduced.The emulsification speed has little effect on the particle size of the emulsion.The rotation speed is small and the particle size distribution is wide.When the rotation speed is large,the particle size distribution is narrow.At the same time,the effects of initial pH value,heating rate,prepolymer concentration and core wall ratio on microcapsules during microencapsulation were studied.Comprehensive factors,optimized preparation conditions,the core-wall ratio is 0.8:1,the initial pH is 3 to 4,and the heating rate is 0.5?/min,the E-51/SM-80 microcapsule product with a coating ratio of 61%is successfully obtained.