| Chemical storage tanks and building exterior wall coatings need to have a good thermal insulation effect,which can block the heat radiation of the sun’s rays and reduce the temperature of the building.At present,the heat insulation effect of coatings is mainly improved by reducing thermal conductivity,increasing reflectivity and emissivity.For petroleum storage tanks,the most frequently used method now is spraying cold water periodically,which will not only cause the waste of water resources,but also accelerate the corrosion and shorten the service life of the storage tank.Thermal insulation and anticorrosive coatings painted on the outer surface of the storage tank can effectively solve this problem.But the oily coatings currently used in large quantities in industry have a high volatile organic compounds(VOC)index,and the large amount of solvent volatilized during use will cause certain pollution to environment.As people pay more and more attention to environmental protection,low-VOC water-based coatings have gradually come into people’s field of vision.Therefore,it is of great significance to develop a water-based coating with both heat insulation and anti-corrosion function.In this paper,based on the principle of radiative and reflective heat insulation,heat insulation and anticorrosion coatings were prepared by selecting titanium dioxide,carbon nanotubes,nano silica,and zirconium dioxide as functional heat insulation pigments and fillers and FEVE emulsion as the resin matrix according to the anti-corrosion requirements of the outer wall coatings.The formulation and preparation process of coatings are discussed,and thermal insulation performance was characterized by measurements of reflectance,hemispheric emissivity,and thermal insulation temperature difference.At the same time,the effect of the type and amount of filler in the composite multilayer structure on the thermal insulation performance was discussed,and the corrosion resistance of the coating(such as salt spray corrosion resistance and artificial accelerated aging resistance)was tested.The experimental conclusions are as follows:The reflectivity and thermal insulation temperature difference of coatings increased gradually and tended to be stable with the increase of the amount of titanium dioxide added in coatings.The optimal amount of titanium dioxide was determined as 25wt% considering the balance between corrosion resistance and cost,at which the thermal insulation temperature difference was 20.8 ℃.In the reflective top layer,an equal amount of synthetic hollow titanium dioxide microspheres is added to replace the solid titanium dioxide particles,so that the thermal insulation temperature difference of the coating can be further increased by 2.7 ℃.Carbon nanotubes and nano silica were used as radiative pigments and fillers in the system,which endowed radiative layer filler with radiation performance to coatings.With the increase of the amount of carbon nanotubes,the reflectivity of the composite coating remained unchanged basically,and the thermal insulation temperature difference increased first,and then became smooth gradually.The reflectance,hemispherical emissivity and thermal insulation temperature difference of coatings reached a high value and the thermal insulation effect was optimal when the amount of carbon nanotubes was 0.6wt%.A further increase of the amount of nano silica did not change the reflectivity of coatings,but the thermal insulation temperature difference increased and then tended to be stable.In the presence of the optimal amount of nano silica of 6wt%,coatings exhibited better reflection and radiation performance,and a thermal insulation temperature difference of 22.1 ℃.As thus,6wt% of nano silica and 0.6wt% of carbon nanotubes were selected as the final radiation layer ratio by considering anti-corrosion and antiaging properties comprehensively.Zirconium dioxide was used instead of carbon nanotubes and nano silica as the fillers for radiative layer to prepare a double-layer reflective and radiative type heat-insulating anticorrosive coating.The thermal insulation temperature difference of coatings showed a trend of first gradually increasing and then decreasing with the increase of zirconium dioxide content.The preferred zirconium dioxide composition was 25wt%,at which the thermal insulation temperature difference was 15.8 ℃.A further incorporation of 25wt% titanium dioxide as a reflective top layer on the radiation layer resulted in an increase of the thermal insulation temperature difference by 9.5 ℃.In summary,when the addition amount of zirconium dioxide is 25wt% and the addition amount of titanium dioxide is 25wt%,the prepared double-layer reflective radiation composite functional coating has good thermal insulation properties,and at the same time has certain corrosion resistance and aging resistance.It meets the national paint film standards and can meet the requirements of actual applications. |
