Abstract:

Objective Polyester (PET) fabrics attracted much research attention in textile fields for its high yield and excellent performance. At present, a variety of methods have been developed to modify polyester fibers with antibacterial, flame retardant, electrostatic, and hydrophobic properties. In addition, hydrophobic modification of polyester fiber plays an important part in applications of medical treatment, filtration, separation, and sanitation. However, PET fabrics with many ester linkages are easily hydrophilic, and can be easily polluted, which seriously limits its applications in ocean envrionment. In order to solve the problem of poor hydrophobicity caused by polar ester groups in the main chain structure of polyester fiber, a fluorine modification strategy is proposed.

Method The simple and efficient hydrophobic modification of the surface of polyester fabrics was carried out by using alkaline solution as etching reagent and trichlorosilane (1H,1H,2H,2H-perfluorooctyl trichlorosilane) as fluoridation modification reagent. The chemical structure, melting point, thermal stability, contact angle, microstructure morphology, and element distribution on surface were characterized by infrared spectroscopy, differential scanning calorimeter, thermogravimetric analyzer, contact angle tester, and scanning electron microscopy-energy disperse spectroscopy, respectively. Moreover, the possible hydrophobic mechanism was analyzed, and the adsorption experiment of petroleum ether by polyester fabrics was also carried out.

Results The results showed that the polyester fabrics demonstrated similar chemical structure and melting point (around 250 ℃) before and after modification. The high thermal stability of polyester fiber before and after modification was beneficial for the adsorption of oil spill at high temperature. The fluorinated polyester fabrics were successfully modified by perfluorosilane, as evidenced by the increased presence of fluorine elements and silicon elements on the surface of the polyester fiber fabrics. In addition, due to the low surface energy of fluoro-silicon polymers, marine fouling organisms would be difficult to aggregate and would fall off the surface of fabrics easily. The maximum thermal decomposition temperature for all samples was found around 448 ℃ after thermogravimetic analysis. Water droplets were absorbed quickly prior to fluorine modification. The hydrophobicity of the fluorinated polyester fabrics was greatly improved, and the water contact angle was as high as (120±5)°. After 1 h of hydrophobicity treatment, the water contact angle was basically constant. Moreover, the hydrophobic mechanism of the fluorinated PET fabrics was revealed in detail. Firstly, perfluorosilane hydrolyzes in ethanol and a large amount of —OH is formed at the end. The polyester fabric after treated with alkaline solution exposes a large amount of —OH and —COOH. The hydrolyzed perfluorosilane works on the surface of the polyester fiber fabrics to form hydrogen bonds, and the small molecular water was removed under heating conditions. In this case, the modifiers containing fluoro-functional groups are chemically bonded onto the surface of polyester fiber fabrics to obtain fabrics with a low surface energy. The polyester fabrics possessed high adsorption capacity for organic solvents, and the adsorption capacity of polyester fabrics for petroleum ether was found to be 8 g/g within 1 min.

Conclusion The development of multifunctional PET fabrics with superhydrophobic properties is considered necessary and urgent. In response to this need, a simple and efficient hydrophobic modification method was conducted on polyester fabrics using an alkaline solution as an etching reagent and trichlorosilane (1H,1H,2H,2H-perfluorooctyl trichlorosilane) as a fluorinated modification reagent. This fluorination process resulted in a significant improvement in the hydrophobicity of PET fabrics, as evidenced by larger water contact angles. The research work conducted in this study provides insight into the mechanism of hydrophobic modification of polyester fabrics, which holds great significance for future studies in this field. In a word, the fluorosilane-coated PET fabrics exhibited several advantages, including a simple preparation process, low cost, and effective performance. Consequently, these fabrics have promising applications in large-scale production and utilization for multifunctional purposes such as antifouling and oil-water separation. Overall, the development of superhydrophobic PET fabrics through fluorosilane coating holds immense potential and offers various benefits for the textile industry.

Key words: polyester fabric, fluorination modification, hydrophobic fabric, oil-water separation, adsorption of marine oil pollution