| Surface coating agent is an indispensable industrial product in modern society manufacturing industry.By designing different chemical structures,changing their physical properties and applying coatings on different substrate surfaces,modern surface coating agent industry has developed rapidly.Hydrophobic coating is a surface coating agent applied on a smooth and neat substrate surface and the static water contact Angle θ of the coating is more than 90°.Hydrophobic coatings are waterproof,chemically stable,anti-aging,heat resistant and have good light transmittance.Because there are only three elements C,F and O in Perfluoropolyether molecules,they have excellent chemical inertia,thermal stability and low surface energy,so they become one of the excellent raw materials for the synthesis and preparation of surface coating agents.With K-type perfluoropolyether carboxylic acid with Mn=6000 and 3,300,allylamine,bis[3-(trimethoxysilyl)propyl]amine,trichlorosilane,dichloromonomethylsilane and monochlorodimethylsilane as raw materials,six kinds of K-type perfluoropolyether silazanes with different molecular weights and different Si-N bond contents were prepared.Among the six kinds of coatings,the best one is made of K6000-PFPE Silazane Si-N(4)with a water contact angle of 118.6±0.5°.The water contact Angle decreases to 97.7±0.5° after 2000 times of reciprocating friction under the action of 1000 g external force,and the friction resistance is the best among the six kinds of perfluoropolyether silazane coatings.The transmittance of the coating was90.99% by UV spectrophotometer.Durability,stability and UV aging resistance test results show that the surface coating agent has excellent thermal stability,acid and salt resistance,excellent durability,and poor alkali resistance.K3300-PFPE mercaptotrimethoxysilane and mercaptotrimethoxysilane were prepared from K-type perfluoropolyether carboxylic acid,diallylamine,3-mercaptopropyl trimethoxysilane and 3-mercaptopropyl trimethoxysilane with Mn=3300 as synthetic raw materials.The structure of K3300-PFPE was characterized by IR and XPS.The water contact angles of the coatings with trimethoxy and triethoxy active groups are 118.2±0.5° and 118.9 0.5° respectively.After 800 times of repeated rubbing of steel wool,the water contact angles of the steel wool and the steel wool decreased to 83.3±0.5° and 81.6±0.5°,and the friction resistance was poor and the hydrophobic effect was lost.The test results of durability,stability and ultraviolet aging resistance show that perfluoropolyether silazane coating agent has excellent thermal stability,acid and salt resistance,excellent durability and ultraviolet aging resistance.The perfluoropolyether trimethoxysilane was prepared from K-type perfluoropolyether carboxylic acid with Mn=6000,allylamine and trichlorosilane,and its structure was characterized by IR.The water contact angle of the coating surface is115.7±0.5°.After repeated rubbing of steel wool for 1000 times,the water contact angle decreased to 91.5±0.5°.After standing at room temperature for 6 months,the contact angle of water decreased by about 1.3°.The test results of light transmittance,stability and ultraviolet aging resistance show that perfluoropolyether trimethoxyalkane coating agent has excellent thermal stability,acid and salt resistance,ultraviolet aging resistance and high light transmittance.The perfluoropolyether-based coating agent with the best effect among the three systems was selected and applied to PET film,stainless steel sheet and non-woven fabric substrate.The results show that the water contact angle of the coatings prepared by perfluoropolyether coating agent on the surfaces of these three substrates is very high,and the excellent hydrophobic properties are still maintained. |
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