Poly(vinyl chloride) surface modification using tetrafluoroethylene in atmospheric pressure glow discharge

Atmospheric pressure glow plasma was used to modify the inner surface of a commercially available poly(vinyl chloride) (PVC) tube sample to enhance the biocompatible properties by polymerizing tetrafluoroethylene (TFE). The composition and properties of the modified surface were similar to those of PTFE. X-ray photoelectron spectroscopy (XPS) of the TFE-coated surface revealed an F1s peak at approximately 689 eV and a C1s at approximately 292 eV. The TFE-coated surface had a surface fluorine concentration as high as 63% with a conspicuous absence of chlorine. From attenuated total reflectance Fourier transform infrared analysis of the TFE-coated surface, we obtained high absorbance ratios of A(1200)/A(1720) (PTFE absorbance peak at 1200 cm(-1) versus that of the substrate peak at 1720 cm(-1) due to plasticizer in PVC) indicating a fluorine-rich coated surface. The contact angles of the newly formed surfaces (100-110 degrees) were similar to that of PTFE. Atomic force microscopy showed that the modified surface was less rough than the surface of the substrate PVC. The flow rate of carrier gas (helium) and reactive gas (TFE) influenced the efficiency of surface coating. A helium flow rate of between 500 and 1000 seem (standard cubic centimeters per minute) and TFE flow rate of between 2 and 3 seem were optimal for obtaining a uniform and thick surface coating.