Surface properties of O2-plasma-treated thermoplastic fluoroelastomers under mechanical stretching

Surface properties and structure of an oxygen-plasma-treated thermoplastic fluoroelastomer film under mechanical stretching were investigated using dynamic contact angle, X-ray photoelectron spectroscopy and field-emission scanning electron microscopy. The contact angle of water on the surface decreased from 96° to 36° by the plasma treatment. The contact angle increased under uniaxial stretching: the plasma treatment effect decreased. This was considered to be due to a dilution of the plasma-oxidized chains through the surface exposure of the matrix embedded chains by stretching. In other words, under stretching, the surface of plasma-treated films can be regarded as being chemically heterogeneous and being composed of treated and untreated parts. On the contrary, by the new surface modification procedure, that is, in situ plasma treatment under stretching, high hydrophilicity and high surface oxygen concentration were found to be maintained even at a high stretching ratio.