Preparation And Properties Of Semi-IPNs Durable Superhydrophobic Coatings

The lotus-leaf mimetic superhydrophobic coating has attracted much more attention due to its unique properties,such as self-cleaning,water-repellency,anti-fouling,anti-fogging,etc.However,most of them often suffer from the poor durability under mechanical force,long-term operation in harch environment,exposure under UV irradiation,and so on,resulting in the loss of superhydrophobicity.Thus,improving the durability of superhydrophobic coatings and expanding their lifespan have become one of important and urgent topics in recent years.It is well-known that the combination of hierarchical roughness and low surface energy is necessary for the creation of superhydrophobicity.Based on this principle,one promising approach for fabrication of durable superhydrophobic coating is to form a bulk material that possesses low-suface-energy roughness throughout its entire volume.By taking advantages of semi-interpenetrating networks（semi-IPNs）,two kind of robust superhydrophobic coatings are fabricated through a one-step spraying method in this disertation,using fluorocarbon-based polyurethane and polyvinylidene fluoride-hexafluoroethylene（PVDF-HFP）（Mw:455,000）as the first and second networks,respectively.The fluorinated attapulgite or commercial silica nanoparticles（Si O₂ NPs）are also incorporated to achieve multiscle surface roughness.The influence of PVDF-HFP contens on the dispersion of nanoparticles and fluorocarbon resin（FC-Resin）in the resultant superhydrophobic coating is studied.The positive effect of PVDF-HFP on the durability of superhydrophobic coatings is also discussed.（1）By virtue of the high specific surface area and strong adsorption feature of attapulgite,a kind of fluorinated attapulgite is prepared by St（?）ber method,using tetraethyl orthosilicate（TEOS）as precursor,ammonia as catalyst and trifluorooctyl triethoxysilane（PFOS）as fluoride agent.The optimization of TEOS content,PFOS content and modification process are performed.The fluorinated attapulgite with good rod structure is eventually achieved through a dropwise addition method with 1.68 m L of TEOS,3.32 g of PFOS and 6 m L of ammonia.（2）Based on the reaction between hydroxyl group and isocyanate,a kind of spray dispersion is firstly formulated by dissolving FC-Resin,fluorinated attapulgite,polyvinylidene fluoride-hexafluoroethylene（PVDF-HFP）and isocyanate curing agent（Tri-NCO）,successively.The superhydrophobic coating is then fabricated by spraying the obtained dispersion in one step.The results show that the addition of 12.0 wt%PVDF-HFP is helpful to form a sem-IPNs with FC-based polyurethane as the first network and PVDF-HFP as the second one.It greatly improves the dispersion and immobilization of fluorinated attapulgite in the coating,achieving accepatable superhydrophobic durability in acid solution for 7 days,300 cycles of rubbing,UV irradiation for 110 h,respectively.（3）Owing to the cost-efficient and easy availabiliy of commercial hydrophobic Si O₂nanoparticles,a sem-IPNs superhydrophobic coating is preapared by a one-step spray method,also using FC-based polyurethane as the first network and PVDF-HFP as the second one.The results show that both the mechnical properties and durability of the superhydrophobic coatings are greatly improved.The coating deomstrates good superhydrophobility even after being immersed in acid,alkali and salt solution after 7 days,respectively,300 cycles of rubbing and 110 h of UV irradiation,which shows potential applications in the industrial fields.