Fluoroalkylation of Textile Surface by Fluoro Silane Coupling Agents

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Novel multi-chain silane coupling agents having end-capped fluoroalkyl group have been synthesized. Glass surface was modified by multi-chain as well as single-chain silane coupling agents as a model of cellelosic fibers. From contact angle measurements, surface free energies were determined, and the surface was proved highly water and oil repellent. Especially, multi-chain type silanes were more reactive and effective than single-chain type silane. The linear correlation was observed between the area ratio of the F_<ls> peak to the Si_<2p> peak. The structure of siloxane layr can be discussed in terms of network interphase model.Surface modification of polyester was also examined using single-chain and multi-chain silane coupling agents having end-capped fluoroalkyls. All silane coupling agents reduced the surface free energy of polyester to 9-12mJ/m^2 for dispersive component and 3-8mJ/m^2 for polar component, respectively, and all the surfaces changed to excellent water-and oil-repellent. In ESCA measurements, as there exists a C_<ls> peak attributable to the C=O of polyester, the thickness of siloxane layr on the surface can be evaluated less than 50 A.The solvent durability of modified surface was evaluated using contact angle and ESCA measurements. Though all modified surfaces have durability against dodecane, xylene, ethyl acetate, tetrachloro ethylene, and hydrochloric acid, long time immersion in Freon reduced the oil-repellency of some surfaces modified with single-chain and multi-chain silanes having short fluoroalkyls. Especially, the immersion in alkaline solution would destroy siloxane network and reduced their water-repellency while their oil-repellency interestingly unchanged. The modification mechanism is also discussed in terms of thermal anchoring.