Preparation And Properties Of Antifogging Coating Solution For Greenhouse Film

Polyethylene（PE）greenhouse film has a low free energy surface,and water vapor can easily condense into droplets on the inner surface.Fog droplets can severely reduce the light transmission of the film and affect the photosynthesis of crops,resulting in lower production and quality.The main method of eliminating fog from greenhouse films is to prepare hydrophilic coatings for them,and currently the use of organic-inorganic hybrid materials to prepare antifogging coatings has become a hot topic.There are many researchers who have explored this material,but the studies they have done also have their own shortcomings.For example,the antifogging duration is short,the light transmission is inferior,the abrasion resistance is inferior,the coating does not have self-healing performance,especially almost no one has tested the antifogging ability of the coating under dry and wet cycle conditions.In this study,organic-inorganic hybrid coatings were prepared on the surface of PE greenhouse film.The chemical composition,surface morphology and wettability were analyzed.Its antifogging properties,light transmission,abrasion resistance,self-healing properties,and wet and dry cycle capabilities were explored in depth.The main studies are as follows:（1）Polyvinyl alcohol（PVA）/Al₂O₃ antifogging coating solution was prepared by blending PVA and nano aluminum sol,and coated on the surface of PE film by dipping method.FTIR,XPS,SEM,EDS,AFM,contact Angle test and other methods were used for characterization.The results show that Al₂O₃ dispersing in PVA is very uniform,and C-O-Al bond is formed between them,which enhances the water resistance and service life of the coating.The contact angle of the coating is 21.1°,and the antifogging life exceeds 60 d in a hot fog environment at 60°C.The transmittance of PVA/Al₂O₃ coated film at 500 nm is 3.5%higher than that of blank PE film.Scratches were created on the coated surface using an HB pencil and later placed in a thermal fog environment at 60°C.The scratches were completely repaired after 10 h.（2）The polyvinyl pyrrolidone（PVP）/Al₂O₃ antifogging coating solution was prepared by a co-blending method using PVP and nano aluminum sol,and coated on the surface of PE films using the dip coating method.The coating was characterized by FTIR,SEM,EDS,AFM and contact Angle test.The results show that Al₂O₃ dispersing evenly in PVP.In the region with wavelength less than 380 nm,the transmittance of films containing PVP is poor.When the wavelength exceeds 380 nm and enters the visible wavelength range,the transmittance of films containing PVP exceeds that of blank PE films.The transmittance of the film coated with PVP/Al₂O₃ coating at 500 nm is 1%higher than that of the blank PE film.The contact angle of the coating is 36.1°,and the antifogging life is over 30 d under thermal fog conditions at 60°C.（3）The sodium alginate（SA）/Si O₂ antifogging coating solution was prepared by a co-blending method using SA and nano-silica sol.A small amount of aziridine crosslinker is added to make SA partially crosslinked and finally coated on the surface of PE film by dip coating method.The coating was characterized by FTIR,XPS,SEM,EDS and AFM.The results show that Si O₂ forms uniform spherical protrusions on the surface of the coating,which increases the roughness of the coating.And the higher the Si O₂ concentration,the better the wettability of the coating.The best antifogging effect is achieved when the ratio of SA and nano-Si O₂ is 4:3,and the effective antifogging time can reach more than 144 h under the heat fog at 60°C.The coating was subjected to 20 dry and wet cycles and friction tests respectively,and the coating still had good antifogging capability.The XPS test results show that SA is the main component that makes the coating have wet and dry cycle effect,and Si O₂ is the main component that makes the coating have good wear resistance.