Elastic Hollow Particles Prepared From Pickering Emulsion And Their Application In Low Shrinkage Coating

It's well-known that photopolymerized materials have many problems with curing shrinkage which is caused by decreasing intermolecular distance from van der Waals force into covalent bonds.Shrinkage occurring in the curing process is a major drawback for current applications such as dental and coating materials,which lead to products warpage,shorten service life and a great number of economic loss.Now elastic hollow particles have been prepared to decrease the photopolymerization shrinkage because hollow particles not only can be used as reactive filler,but also elasticity can counteract shrinkage stress.The main contents of this work can be divided into three parts and they're listed as follow:1?The amino group functionalized silica nanoparticles?SiO₂-NH₂?are used as particle emulsifiers obtained from a classical St?ber process.After that,we use SiO₂-NH₂nanoparticles to stabilize O/W Pickering emulsion.The effects of SiO₂-NH₂ concentration,pH,oil-water volume ratio,stirring rate and emulsification time on emulsifying properities are studied in this part.PU-SPUA hollow particles are prepared from Pickering templates by reactant IPDI in the oil phase interreacting with amino group on the surface of SiO₂-NH₂ nanoparticles and hydroxyl group of H₂O at the oil-water interface.The diameter of PU-SPUA is 5²0?m and shell thickness is 100²00 nm observed though SEM.However,PU-SPUA hollow particles are prone to collapse due to their thin shell and has a poor solvent resistance;2?In order to improve the mechanical properties of hollow particles templated from Pickering emulsion,the oil phase was composed of solvent butyrolactone?GBL?,reactant glycidyl methacrylate?GMA?and polyurethane acrylic resin?RY2203?,and photoinitiator1173.After forming Pickering emulsion droplet,PUA hollow particles are obtained by applying UV light to initiate the interfacial polymerization.In this part of work,we adjust the location where SiO₂-MPS are dispersed and the concentration of component in oil phase to study their effects on the properties of PUA hollow particles.Though SEM,Nanoindentation and nano tensile test,we know that PUA hollow particles are fabricated successfully with swithable morphology and mechanical properties;3?After synthesis and characterization of PUA hollow particles,we add different ratios of PUA hollow particles into UV curing coating foluma to study the effects of PUA hollow particles on the photopolymerization process.The experimental results of photorheology,RT-FTIR,DMA,TGA and basic properties of cured film indicated that PUA hollow particles could reduce the photopolymerization shrinkage without influencing cured film performance and reaction kinetics of photopolymerization.