Water permeation of SiO2-CH3SiO3/2 thin films modified with trimethylsilyl groups on nylon-6 substrates

SiO2-CH3SiO3/2 thin films coated on nylon-6 substrates by the sol-gel method were modified with trimethylsilyl (TMS) groups and their water permeability was evaluated. The water permeability coefficient of the nylon-6 substrates coated with TMS-modified SiO2-CH3SiO3/2 thin films was smaller than that of unmodified ones. The wettability for water of SiO2-CH3SiO3/2 thin films modified with TMS was smaller than that of unmodified ones. The decrease in the wettability by the modification with TMS resulted in the decrease in water permeability. The measurements of pore size distribution and the water permeability coefficient of coating films with different pressures of upstream side suggested that the mechanism of permeation was governed by the capillary condensation flow. This mechanism was also supported by the result that the water permeability coefficient was decreased with a decrease in wettability.