Study On Hydrophobic Modification Of PET Substrate By Ultraviolet Induced Emulsion Graft Polymerization

Polyethylene terephthalate（PET）is a polymer material with excellent comprehensive properties,which is widely used in textile,package,electronics,biomedical materials,separation and filtration and so on.However,PET is not a kind of material with high surface hydrophobicity,which limits its application in self-cleaning,antifouling and other fields.Constructing micro-/nano-rough structures on the substrate surface is an effective way to prepare superhydrophobic surface.However,the commonly used methods such as etching,electrospinning,template,chemical deposition,coating still have issues of treating complex processes,high costs or lack of covalent bonding between the coating and the substrate.Compared with other methods,UV-induced photograft polymerization has the advantages of simple equipment,fast reaction rate,no damage to the bulk properties of material,ability of continuous processing,temporal/spatial controllability,making it unique in surface modification of polymer materials.Based on this background,this dissertation proposes a strategy of fabrication hydrophobically modified PET surface by constructing micro-/nano-structures by UV-induced emulsion graft polymerization.The main research contents and results are as follows:1.Surface hydrophobic modification of PET film was achieved based on UV-induced 2-（perfluorooctyl）ethyl methacrylate（FOEMA）emulsion graft polymerization.Attenuated total reflection Fourier transform infrared spectroscopy（ATR-FTIR）and X-ray photoelectron spectroscopy（XPS）characterization results showed that the characteristic peak of CF₂ groups appeared on the modified film surface,and the content of fluorine reached45.72%,confirming that grafting reaction proceeded successfully.The effects of grafting reaction conditions such as illumination intensity,illumination time,monomer concentration,emulsifier concentration and type on grafting density were explored.When the monomer concentration was 40 wt%and the emulsifier cetyltrimethylammonium bromide（CTAB）concentration was 8 wt%,the grafting density on the modified film surface was 276.12μg/cm² after reacting for 8 min under UV light with an illumination intensity of 9000μW/cm².Scanning electron microscope（SEM）characterization results showed that micro-/nano-scale grafted particles could be introduced on the PET film surface by the emulsion photograft polymerization.When the monomer concentration was 20 wt%and the emulsifier CTAB concentration was 4 wt%,Atomic force microscope（AFM）characterization results showed that the surface roughness of PET film increased from 1.77 nm to 168 nm after reacting for 2 min under UV light with an illumination intensity of 9000μW/cm².And the water static contact angle（WCA）on the modified PET film surface could reach 120.5°,which was 35.1°higher than that of blank PET film.2.A novel method that can introduce hydrophobic micro-/nano-particle structures on the PET film surface via UV-induced emulsion graft polymerization and silane coupling reaction was developed.Firstly,the surface micro-/nano-rough structures on PET substrate were constructed by the emulsion graft polymerization ofγ-methacryloyloxypropyltrimethoxysilane（KH570）under ultraviolet light irradiation.The effects of reaction conditions on grafting density were explored,and it was found that when the monomer concentration was 50 wt%and the emulsifier concentration was 10 wt%,the grafting density could reach 489.17μg/cm² after reacting for 12 min under UV light with an illumination intensity of 9000μW/cm².SEM characterization showed that a coarse layer formed by loosely packed spherical particles with diameter of about 100 nm was formed on the PET film surface.The hydrophobical modification of PET film was achieved by hydrolysis of the methylsiloxane groups in grafted particles and further hydrolysis-condensation reaction with trimethoxyheptadecafluorodecylsilane.The surface modification process of PET film in different stages were confirmed by ATR-FTIR and XPS.SEM observation showed that hydrolysis and coupling reaction had no influence on the surface micro-/nano-structures.The surface roughness of modified PET film could reach 133 nm and the fluorine content could reach60.28%.In addition,the WCA on the modified PET film surface could reach139.2°,which was 53.8°higher than that of blank PET film.