The surface of polypropylene mesh sheets was sulfonated by heating in liquid H2SO4. Diffuse reflectance Fourier transform infrared spectroscopy confirmed that SO3H groups are immobilized on the surface and their amount increases with increasing treatment lime. The hydrophilicity of the samples was examined by following the time-dependence of the uptake weight of H2O (W-L) after immersion in liquid H2O. It was shown that the intercept in the plots of In W-L vs. In t provides quantitative information on the wetting property of the surface. The simulation based on Washburn’s theory predicted the limited intercepts with sulfonation.