| 초록 |
Plasma treatment is a useful method of converting hydrophobic polymer surface to hydrophilic surface for the purpose of improving wettability and adhesion properties without changing bulk properties. But polymer shows hydrophobic recovery only after plasma treatment in the air because the mobility of polymer chains enables polymer surfaces to respond to interfacial forces and to adapt their surface chemical structure to their environment. However, the surface rearrangement (i.e., the aging) of the plasma treated polymers can be prevented by restricting the dynamic nature of the macromolecular chains at the surface. This can be achieved, for instance, by increasing the crystallinity and degree of cross-linking at the surface. The present investigation studies the behavior of plasma-incorporated polar functional groups on the surfaces of polyethylene of different surface crystallinity by using angle resolved X-ray photoelectron spectroscopy (XPS) and near edge x-ray absorption fine structure (NEXAFS) spectroscopy. The orientation of polar groups during aging time was also observed using angular dependence of NEXAFS resonance intensities. The aging effect has been observed to be lower in the sample of higher degree of crystallinity and this is explained due to lower reorientation and diffusion in the surface. From X-ray absorption study with oxygen plasma treated PE, the difference of chain movement between low and high crystalline polymer can be observed in real time during aging time. |
