Preparation And Properties Of Waterborne High Infrared Reflective Energy-Saving Coatings

Traditional solvent-based heat-insulating and energy-saving coatings is used as the coatings of exterior wall of buildings.These coatings have high solar reflectance,which can effectively relieve solar heat energy from entering the interior of the building and reduce the energy consumption of refrigeration equipment.The materials are usually synthetic resins and mostly solvent-based resins,which contain more volatile organic compounds?VOC?.With the improved awareness of environmental protection among citizens,an increasing voice of environmental protection is arising.The traditional solvent-based thermal insulation energy-saving coatings are gradually replaced by the water-based thermal insulation energy-saving coatings.The base material of water-based thermal insulation energy-saving coatings is usually water-based emulsion with a very low or even no content of VOC,which can effectively improve the ecological environment and save energy.The natural materials,which had a wide range of sources,were used to prepare the water-based nitrocellulose?WNC?emulsion.At the same time,traditional nitro lacquer has a long history and well-established preparation technology.Therefore,based on the preparation technology,the base material,nitrocellulose?NC?,was used to prepare a water-based thermal insulation energy-saving coating with high infrared reflectivity.This article used NC as the base material,isophorone diisocyanate?IPDI?,epoxy resin E-44,polyethylene glycol 200?PEG200?and polyethylene glycol 2000?PEG2000?as the raw materials.A hydrophilic group,an epoxy group,and a urethane group were introduced in the NC molecule to prepare an emulsified aqueous nitrocellulose?WNC?emulsion.The analyzing results of the particle size,stability and thermal weight loss of the emulsion showed that:1)When the molecular weight of PEG is larger,the more hydrophilic segments are introduced in NC molecule,which resulting in the smaller particle size,the narrower distribution,and the better stability of the emulsion.Moreover,it is found that the particle size of the raw material PEG6000 used for the emulsion is much smaller than the particle size prepared by PEG2000.When the particle size of the emulsion is less than 300nm,the stability of the prepared WNC emulsion is better;2)When m?PEG-2000?:m?IPDI?is greater than 2.7:4,the prepared WNC has a bluish blue color,small particle size,and stable emulsion;3)The stability of the emulsion is better when m?NC?:m?E-44?is below 1:3.24;4)The average particle size of the prepared emulsion with excellent comprehensive performance is140.3nm,the dispersion coefficient PDI value is 0.138,the emulsion is spherical,the thermal stability is good,the main weight loss temperature is in the range of 150?⁴03?.The curing of the WNC coating was conducted using triethylenetetramine,amino resin and modified amine.The water absorption,water resistance,wear resistance,flexibility,hardness,et.al.of the paint film were tested.The best curing process is obtained:According to m?amino resin?:m?WNC?ratio of 1:10,the curing process of130?for 20min is chosen.The hardness of the paint film is 4H and the adhesion is 0.The water absorption rate is 6.5%.The abrasion rate is 3.35%and the flexibility is 2mm.Besides,the surface of the paint film is smooth and flat.Using self-made WNC as the base material,the solar reflectance test of the coating was carried out by studying the influence of the type and amount of pigment and filler,the particle size of hollow glass microbeads,the combination of pigment and filler,and the thickness of the coating on solar reflectance.The experiment tests,such as abrasion resistance,scrub resistance,water resistance,alkali resistance and impact resistance performance,were conducted and analyzed.The results were concluded:1)The pigment and filler TiO₂ and hollow glass microbeads mainly affect the solar reflectance.When the optimal usage of TiO₂ is 30%,the coating has a high solar reflectance,good wear resistance,flexibility,adhesion,hardness and other properties;2)When the particle size of the hollow glass microbeads is 25⁷0?m with the content of 25%,the coating has good solar reflectance and mechanical properties.The good solar reflectance leads to an improved energy saving ability;3)The best experimental formula obtained through orthogonal experiments is 6g TiO₂,3g hollow glass beads,3g ZnO,2g sericite powder,10g aqueous NC emulsion and 10g distilled water;4)Based on this formula,the reflectivity of the energy-saving coating to sunlight can be as high as 92.15%,which is better than 90.5%of the commercially available heat-insulating energy-saving coatings;5)The thickness of the coating has a great influence on the reflection of sunlight.The coating thickness is around 450?m.The water-based nitrocellulose?NC?emulsion is used as the basic film-forming substance to prepare water-based high-infrared reflective energy-saving coatings.The products have a good comprehensive application performance and promotion and application value.