| Water-bearing capsule refers to an object having a core-shell structure formed by encapsulating water or aqueous solution with a natural or synthetic film-forming material,which has important application value in some specific fields such as foods,tobacco,cosmetics,and pharmaceuticals.Liquid marble is compound droplet formed by adsorption of hydrophobic inorganic or polymeric particles on the surface of water droplets to stabilize the gas-liquid interface.Their uniform and controllable particle size and simple process provides a new idea for the preparation of water-bearing capsule.However,due to the porous nature of the shell made of hydrophobic particles,the liquid inside the liquid marble quickly evaporates,which seriously affects the preservation and stability of the water-bearing capsule.How to suppress the volatilization of liquid inside the marbles and increase its pot life and storage period is a key issue that needs to be solved urgently.The UV-curing technology has the advantages of high production efficiency,low energy consumption,fast curing,no solvent,no pollution to the environment,low process cost,curing at room temperature,and space saving.Under UV light,the photoinitiator can rapidly generated free radicals or ions,initiating polymerization and cross-linking of the prepolymer and reactive monomer into a network structure,and achieving instantaneous conversion from the resin(liquid)to the polymer(solid).The UV-cured coating has good moisture barrier properties.The presence of impenetrable graphene oxide and montmorillonite nanosheets in the polymer matrix,increases the diffusion path and consequently decreases of the gas permeability of the composite.Based on above analysis,in this study,liquid marble was first prepared by encapsulation of water droplet using hydrophobic silicon dioxide particles as a stabilizer of liquid-gas interface.Then the as-prepared liquid marble was packaged using a polymer coating by moisture curing of ethyl ?-cyanoacrylate on its surface to prepare water-bearing capsule.The water-bearing capsule was further encapsulated by a UV-cured coating or montmorillonite,and graphene oxide composite.The main research work is as follows:1.Preparation of water-bearing capsule by encapsulating liquid marble with UV-cured coating and its performance.Liquid marble was prepared by encapsulation of water droplet using hydrophobic silicon dioxide particles as a stabilizer of liquid-gas interface.The morphology of liquid marble wascharacterized by SEM,digital camera and so on.Then the as-prepared liquid marble was packaged using a polymer coating by moisture curing of ethyl ?-cyanoacrylate on its surface.After curing,poly(ethyl ?-cyanoacrylate)-encapsulated water-bearing capsule was obtained.The morphology of poly(ethyl ?-cyanoacrylate)-encapsulated water-bearing capsule was characterized by SEM and digital camera.Epoxy acrylate,acrylated epoxidized soybean oil,and urethane acrylate,were respectively coated on the surface of poly(ethyl ?-cyanoacrylate)-encapsulated water-bearing capsule to obtain UV-cured coating-encapsulated water-bearing capsule.The double-bond conversion of the UV-cured coating was investigated by the real-time FT-IR.The basic properties such as hardness,water resistance were studied,and the mechanical performance and water retention capacity of the water-bearing capsule were also studied.The results indicated that the water-bearing capsule was basically spherical,and the porous shell of the liquid marble was composed of silicon dioxide particles.The shell of the water-bearing capsule became a dense polymer membrane,and the water volatilization rate was significantly reduced.The UV-cured coating-encapsulated water-bearing capsule had a glossy surface and a uniform coating thickness.Compared to the poly(ethyl ?-cyanoacrylate)-encapsulated waterbearing capsule,the mechanical performance of the UV-cured coating-encapsulated waterbearing capsule was significantly improved.With the increase of the layer of UV-cured coatings,the mechanical properties of the water-bearing capsule rapidly increased,and the water evaporation rate of the water-bearing capsule was significantly reduced,the time needed for water evaporation was extended from 1 day to 7 days at 30 ? and 30 RH%,and gradually decreased with the increase of the layer of UV-cured coatings.When four layers of UV-cured coatings were applied,the water content in the resulting water-bearing capsules remained 47.1% after 8 days at 35 ? and 30 RH%.The poly(ethyl ?-cyanoacrylate)coating and UV-cured coating endowed the water-bearing capsule with both excellent water vapor barrier property and mechanical performance,making it a great potential to be applied in cosmetics,pharmacy,and cigarette.2.Preparation of water-bearing capsule by encapsulating liquid marble with montmorillonite-based composite UV-cured coating and its performance.MMT-CTAB was first prepared by ion exchange of cationic surfactant hexadecyl trimethyl ammonium bromide(CTAB)with montmorillonite.MMT-CTAB-MPS was prepared by reaction of silane coupling agent 3-(methacryloyloxy)propyltrimethoxysilane(MPS)with MMT-CTAB.Then the organic montmorillonite and acrylated epoxidized soybean oil(AESO)resin were uniformly mixed to prepare montmorillonite-based composite UV-cured resin.The double-bond conversion of the UV-cured composite coating was investigated by the real-time FT-IR.The basic properties such as hardness,solvent resistance were studied.The crosssectional morphology and thermal stability of the composite were characterized by SEM and TGA.The water-bearing capsule was further prepared from montmorillonite composite coating.The morphology of the montmorillonite composite coating-encapsulated water-bearing capsule and its water retention capacity were also studied.The results indicated that the montmorillonite was flaky,and the interlayer spacing of the montmorillonite was increased after modified by CTAB;As the content of organic montmorillonite increased,the pendulum hardness and thermal stability of the composite coating gradually increased,and the final double bond conversion and transmission rate gradually decreased;With different addition amounts,the organic montmorillonite was well dispersed in AESO,and its interlayer spacing further increased;Compared to pure AESO encapsulated water-bearing capsule,the montmorillonite composite coating-encapsulated water-bearing capsule had a darker color and the water evaporation rate was further reduced;When four layers of a composite coating containing 5 wt% of MMT-CTAB and 5 wt% of MMT-CTAB-MPS were applied,the water content in the resulting water-bearing capsules remained 53.3% and 53% after 8 days at 35 ? and 30 RH%,respectively.It is probably due to the montmorillonite filler extends the diffusion path of water vapor in the polymer,thereby reducing the water vapor transmission rate of the composite coating.3.Preparation of water-bearing capsule by encapsulating liquid marble with graphene oxide-based composite UV-cured coating and its performance.The graphene oxide(GO)was prepared by a modified Hummers method and organically modified.The organic GO and AESO resin were uniformly mixed to prepare graphene oxide UV-cured composite resin.The morphology of graphene oxide was investigated by digital camera,SEM and AFM.The double-bond conversion of the UV-cured composite coating was investigated by the real-time FT-IR.The basic properties such as hardness,solvent resistance were studied.The cross-sectional morphology and thermal stability of the composites were characterized by SEM and TGA.The water-bearing capsule was further prepared from graphene oxide composite coating.The morphology and water retention capacity of the waterbearing capsule encapsulated by the graphene oxide composite coating was also investigated.The results indicated that graphene oxide was flaky.The layer spacing of GO was increased after modified by ODA,MDI and HEMA.It was found that as the content of GO increased,the pendulum hardness and the final double bond conversion of the composite coating gradually decreased,and the thermal stability and transmittance also gradually decreased;Compared to pure AESO-encapsulated water-bearing capsule,the graphene oxide composite coatingencapsulated water-bearing capsule was black and the water evaporation rate was further reduced;When four layers of composite coating containing 3 wt% of GO-ODA and 3 wt% of GO-MDI-HEMA were applied,the water content of the resulting water-bearing capsules remained 53.1% and 52.6% after 8 days at 35 ? and 30 RH%,respectively. |
PDF Full Text Request