UV-grafted gradient surface polyurethane membrane

Gradient surfaces of polyurethane (PU) membranes were created by UV grafting approach in a graded temperature field. Acrylic acid was selected as grafting monomer to improve the hydrophilicity of the surfaces. The Fourier transform infrared spectroscope (FTIR) spectra and scanning electronic microscope (SEM) were used to characterize the gradient. The results showed that the graft yield increased gradually from the lower temperature end to the higher temperature end. As a result, the hydrophilicity of the gradient surfaces displayed a gradual change along the same direction. Water contact angle measurements also proved this point. The graft reaction rate was investigated as a function of positions along the PU membrane. The average grafting yield of PU membrane increased with the extending of UV light irradiation and increase of photo initiator dosage.