Preparation,Properties And Applications Of Fluorine-free Anti-smudge Coatings

Anti-smudge coatings are a kind of functional coatings with a smooth surface and a low surface energy based on polymer modification.They generally demonstrate self-cleaning and anti-graffiti properties,which allow water-and oil-borne liquids to slide off their surfaces without leaving any traces.Therefore,they can be used for the self-cleaning of windows,the anti-graffiti of public facilities,and the drag reduction of crude oil transportation pipelines,etc.,showing tremendous potential for practical applications.However,the current preparation of anti-smudge coatings mainly has the following disadvantages.First,fluorine-containing compounds are usually used to modify the matrix resin to reduce the surface energy of the coatings.However,they are expensive.And the use of long-chain perfluorinated compounds with biological toxicity and bioaccumulation will exert detrimental effect on human and environment.Second,the existing anti-smudge coatings are basically prepared from non-renewable raw materials,which is not good for the sustainable development of anti-smudge coatings.Third,a long-time thermal curing is usually adopted for the preparation of anti-smudge coatings,which not only limits the application of these coatings on heat-sensitive substrates but also increases the curing energy consumption.Fourth,there are few studies about water-borne anti-smudge coatings,and the anti-smudge properties of the coatings will be deteriorated if the hydrophilic groups in the water-borne components have not been eliminated.In view of above problems,safe and non-toxic polydimethylsiloxane(PDMS)was used to replace fluorine-containing compounds to provide coatings with low surface energy.And a series of novel fluorine-free anti-smudge coatings were prepared.(1)A bio-based fluorine-free anti-smudge coating was prepared based on castor oil modification,which made the renewable raw materials used in anti-smudge coatings.The as-prepared coating was highly transparent,and its surface was fairly smooth with a root-mean-square roughness of 0.314 nm.Water,hexadecane,pump oil,crude oil could slide off the coating surface without leaving any residues.Also,the coating demonstrated excellent chemical stability and self-cleaning performance.And it could be used for anti-fingerprint and anti-graffiti purposes.In addition,dyes could be added into the coating system without compromising its anti-smudge properties,and thus colored anti-smudge coatings could be prepared.(2)A fluorine-free anti-smudge coating that could be cured by ultraviolet(UV)light and sunlight was prepared,and the UV curing time was only 35 s.This coating system could avoid the influence of long-time thermal curing on the substrates,allow the application of fluorine-free anti-smudge coatings on the heat-sensitive substrates,and shorten the curing time,making it more suitable for industrial production.This fluorine-free anti-smudge coating possessed high transparency,and it could be applied onto glasses,tiles,tin plates,phone touchscreens,plastics,and other substrates to endow them with self-cleaning and anti-fingerprint performances.(3)A hyperbranched polyester-based fluorine-free anti-smudge coating was developed by introducing hyperbranched system to the preparation of anti-smudge coating.When the PDMS content was 0.5 wt%,the as-prepared coating was highly transparent.And the coating demonstrated excellent self-cleaning,anti-fingerprint,and anti-graffiti performances.After being immersed in a strong acid solution(p H = 0)and a strong alkali solution(p H = 14)for 15 hours,the coating retained excellent anti-smudge properties,indicative of the excellent chemical stability of the coating.In addition,the coating also exhibited exceptional impact resistance,flexibility,hardness,adhesion,and abrasion resistance.After 5000 abrasion cycles,water and hexadecane droplets could slide off the coating surface without leaving any traces.(4)A water-borne fluorine-free anti-smudge coating was prepared by using a synthesized water-borne PDMS-modified polyacrylate(WPMPA)and a water-borne trifunctional aziridine curing agent(TTMAP)as raw materials.The heavy crosslinking density of the coating was provided via the reaction of the hydrophilic groups in these two water-borne components(the reaction of the carboxyl groups in WMPPA and the aziridine rings in TTMAP)during the curing process,which also avoided the residue of the hydrophilic groups in the water-borne components.The as-prepared water-borne fluorine-free anti-smudge coating was highly transparent.It was found that,on this coating surface,the liquids miscible with PDMS exhibited a lower sliding angle than the ones immiscible with PDMS,which was because the miscible ones could swell the PDMS chains on the coating surface and thus reduced the sliding friction between the liquids and the coating surface.In addition,the coating could be used for anti-fingerprint and anti-graffiti purposes,and it also demonstrated excellent chemical stability,adhesion,impact resistance,and UV aging resistance.