| Transparent heat-shielding coating is a new type of coating that absorbs and shields near infrared and ultraviolet light.It is coated on building windows,glass curtain walls and other building glass structures.Under the premise of ensuring high visible light transmittance,it increases the heat-shielding effect to achieve the purpose of energy saving and emission reduction.Antimony doped tin oxide(ATO)is one of the mainstream transparent heat-shielding materials at present,but it is easily interfered by free ions and coagulates in polymer latexes,and thus presents poor distribution in polymer matrix and cannot achieve high visible light transmittance as well as heat-shielding effect.In addition,the existing waterborne transparent heat shielding coatings have poor weather resistance and water resistance,which is difficult to ensure long-term performance.In view of the current situation of transparent heat-shielding coatings,the key raw materials including film-forming binders and ATO thermal insulation fillers were developed.A silane-modified polyacrylate latex possesses good compatibility with the transparent thermal insulation filler ATO dispersion,which was prepared by hydrothermal reaction and solvent replacement method.Subsequently the transparent heat-shielding coatings with excellent performance were prepared.(1)In order to avoid the coagulation effect of residual thermal initiator fragments in polymer latexes on functional filler ATO,organic sulfinic acid derivative sodium salt(FF6M)and tert-butyl hydroperoxide(TBHP)were used as redox initiators to prepare the silanemodified polyacrylate latex for transparent heat-shielding coatings.The polyacrylate latex modified by introducing silane coupling agent KH-570 was synthesized by semi-continuous seeded emulsion polymerization.The effects of initiator,synthesis temperature,ratio of soft and hard monomers,and amount of silane coupling agent on the properties of silane-modified polyacrylate latex were investigated.The experimental results show that when FF6M/TBHP is used as the initiator,the theoretical glass transition temperature is of 30°C,and the amount of KH-570 was 6 wt% of the total monomer,the obtained silane-modified polyacrylate latex possesses excellent performance such as the pencil hardness of the coating film reached H,the adhesion is of 0 grade,and passed 168 h water resistance,acid and alkali resistance and 3temperature change cycle tests.The obtained silane-modified polyacrylate latex had good compatibility with ATO dispersion,and met the construction requirements of scraping and spraying.(2)Monodisperse spherical ATO was synthesized by mild hydrothermal method and solvent replacement method.The effects of precursor preparation technology and synthesis temperature on the preparation of ATO were discussed.The experimental results show that the monodisperse spherical ATO synthesized at the reaction temperature of 160°C and the reaction time of 5 h owns an average particle size of 50 nm and good dispersibility in polymer latex to form a stable system.(3)A series of transparent heat-shielding coatings were prepared by mixing the synthesized silane-modified polyacrylate latex and ATO dispersion.The obtained ATO composite coating film possesses excellent transparency,and the transmittance in the whole solar spectrum is60%～80%.When the mass fraction of ATO in the coating was 3 wt%,compared with the blank group,the thermal insulation temperature difference reached 4.9 °C.When the mass fraction of ATO in the coating was 12 wt%,the thermal insulation temperature difference reached 8.1 °C compared with the blank group,the pencil hardness reached 3H from the blank H and the other properties of the transparent heat-shielding coatings were satisfied. |
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