| Fogging is a common natural phenomenon.Fogging on the surface of transparent substrates such as glass or plastic will affect its light transmission ability and bring a series of negative effects to people’s daily life.In addition,fogging may lead to serious health and safety problems in the fields of medical treatment,automobile,food,agriculture and aviation.Constructing antifogging coating on the surface of substrate is a simple and effective antifogging method.Hydrophilic coatings with antifogging properties were prepared according to the specific morphology and specific chemical composition of the solid surface.At present,many preparation methods of anti-fogging coating have been reported,but there are many shortcomings in practical application,such as poor antifogging performance,poor durability and non-environmental protection.Therefore,in this paper,acetone-prepolymer method was used to prepare water-based polyurethane emulsion with little or no solvent and good applicability.Based on this,an antifogging coating with good antifogging performance,lasting antifogging and high transparency was prepared.The main contents of this paper are as follows:(1)In this paper,hydroxy terminated waterborne polyurethane(WPU-OH)emulsion was synthesized with main raw materials: polypropylene glycol,polyethylene glycol,isophorone diisocyanate and pentaerythritol,etc.WPU-OH anti-fogging coating was prepared by adding silica sol,surfactant and curing agent.Then a firmly bonded antifogging coating was formed on PC substrate by thermal curing.In this paper,the properties of coating,such as heat resistance,water resistance,transparency and anti-fog,are discussed in detail.The results showed that the WPU-OH anti-fogging coating combined with reactive surfactant or nonreactive surfactant was colorless,transparent and stable,and the antifogging coating was transparent,smooth and flat.The water contact angle WCA of the coating was less than 10 °,which is close to super hydrophilicity.And the water droplets could spread completely in a very short time.The antifogging test results of mild and high temperature showed that the coating has good antifogging performance.The test result of repeatability showed that WPU-OH antifogging coating had good anti-fogging durability.The results of anti-fogging test after soaking treatment and coating surface morphology test showed that the coating with cross-network structure improved the problems of easy water washing and leaching of surfactant.At the same time,it improved the surface hydrophilicity of the coating and ensures the water resistance.In addition,other characterization test results showed that the coating had good transparency,heat resistance,water resistance and other properties.(2)In this paper,3-isocyanate propyl triethoxysilane coupling agent(IPTES)was introduced into WPU-OH to synthesize siloxane modified hydroxyl terminated waterborne polyurethane(WPU-OH-I)emulsion.WPU-OH-I anti-fogging coating with transparent appearance and good stability was prepared by adding silica sol,curing agent and other raw materials.The results showed that the antifogging coating formed by curing WPU-OH-I was transparent and the surface was flat and smooth.On the surface of the coating,water droplets spread instantly.And it’s attributed to the flexibility of the silane coupling agent at the end of the graft polymer,which carries the-OH that’s not involved in the condensation reaction to the coating surface.Different curing agents have significant effects on the structure and properties of the coating.The coating,with WCA=10.58°,prepared by adding closed isocyanate curing agent XP 2706 was flat,dense and continuous.While the coating,with WCA=6.99°,added amino resin curing agent CY 303 is composed of continuous and dense papillary particles.The antifogging test results showed that the coatings prepared in the experiment had good antifogging performance and antifogging durability.And the hydrophilicity and antifogging of the coatings were related to the chemical properties and structure of the coatings.The research showed that the coating also had good transparency,adhesion and heat resistance. |
