Preparation Of Porous And Hollow Microspheres And Their Thermal Insulation Performance In Photocurable Coatings

Thermal insulation coatings can be used to effectively inhibit heat transfer and slow down temperature rise.They have a wide range of applications in industrial production and daily uses such as buildings,indoor and outdoor instruments,thermal insulation equipments,and oil and gas storage tanks.Compared with traditional thermal insulation materials,they have unique advantages.At present,research on thermal insulation functional fillers mainly focuses on porous materials,hollow microspheres and fillers with infrared reflection function.Among the porous materials,aerogels with excellent thermal insulation properties have inherent brittleness,low tensile strength and high production costs.Hollow microspheres are mainly used in hollow glass microspheres and ceramic microspheres,but their particle size is large,the shell is fragile,and the compatibility with the substrate coating is not good.The fillers with infrared reflective properties mainly include Ti O₂,ITO,ATO,etc.,but after being added to the coating,the thermal conductivity of the coating will be affected and increased,which limits their application in thermal insulation coatings.In response to these problems,this subject has designed three thermal insulation functional fillers with excellent thermal insulation properties based on the thermal insulation mechanism,mainly mesoporous porous microspheres,hollow microspheres with small wall thickness and hollow microspheres that reflect infrared rays.They were added to the UV-curing coating system to realize the thermal insulation performance of the coating.The main research contents are as follows:1.The silica particles with amino groups on the surface were prepared through sol-gel and surface modification.The amino silica particles were used as stabilization colloidal particles.The oil phase was a mixture of styrene,divinylbenzene and isooctane.The aqueous solution of polyvinyl alcohol was the water phase,which was emulsified by the Pickering emulsion template method and post-polymerized to obtain mesoporous polystyrene microspheres（MPS）.The effect of the porogen isooctane on the pore size and porosity of porous polystyrene microspheres（MPS）was also explored.With the increase of isooctane,the pore size of MPS increased from 3.83nm to 14.01 nm,porosity increased from 36%to 40%.MPS exhibits thermal insulation performance equivalent to that of commercially available hollow glass beads（HGB）,and the coating also shows a thermal insulation effect equivalent to hollow glass beads（HGB）in the coating,and it can effectively reduce the thermal conductivity of the coated glass plate from 0.8622 W/m.K to 0.7776 W/m.K.With the increase in the amount of addition,the thermal insulation performance of the coating gradually improves,and the coating with MPS did not appear delamination after being placed for 24 h.After the coating was cured,the transparency of the coating can reach 83.8%and the near-infrared light reflectivity can reach 89.4%,both of which were higher than the commercially available hollow glass beads.2.This chapter designs thin-walled,small-sized hollow silica microspheres（HS）,and systematically studies its effect on the thermal insulation performance of light-curing coatings.First,polyvinylpyrrolidone（PVP）as a dispersion stabilizer,potassium persulfate（KPS）as an initiator,then a positively charged polystyrene template was prepared by soap-free emulsion polymerization.The effect of the amount of PVP and KPS on the particle size of the polystyrene template was studied.In order to make the cavity size as small as possible,the hollow silica microspheres（HS）were prepared by using polystyrene particles with a particle size of 200 nm as a template.It was explored that the more the amount of ammonia,the thicker the thickness of the shell,and the optimal conditions for the removal of the polystyrene template were optimized:500°C,2 h.We selected HS with a thinner shell thickness of 30 nm and unbroken to study its thermal insulation performance.The research founded that in the powder state and when added to the coating,it exhibits better thermal insulation performance than commercially available hollow glass beads and it can greatly reduce the thermal conductivity of the coated glass plate from 0.862188W/m.K to 0.614400 W/m.K.However,excessive addition of HS in the coating will lead to agglomeration and is not conducive to further improving the thermal insulation performance.After HS is added to the coating,the transparency of the coating can be as high as 85%,and did not change significantly with the change of the added amount.3.Comparing the thermal insulation performance of MPS and HS,the hollow structure shows more excellent thermal insulation performance.In order to expand the application range of thermal insulation coatings and combine barrier thermal insulation performance with reflective thermal insulation performance,titanium dioxide has high reflectivity to infrared light.In this chapter,hollow titanium dioxide microspheres（HT）with a smaller cavity size were prepared.In order to make the size of the cavity smaller,200 nm polystyrene particles were used as templates,and titanium dioxide particles were coated on the surface by slow hydrolysis,and hollow titanium dioxide microspheres were obtained after ablation.The influence of the amount of tetrabutyl titanate（TBT）on the thickness of the shell layer,the influence of the amount of ammonia on the particle size of the shell titanium dioxide particles,and the near-infrared light reflectivity of different HT in the coating were studied respectively.Studies have shown that the prepared hollow microsphere is of anatase type.When the shell layer of HT is thicker and the size of the titanium dioxide particles in the shell layer is smaller,the near-infrared light reflectivity of the coating can reach up to 63.8%.The coating added with HT also exhibits excellent barrier thermal insulation and reflective thermal insulation performance.