CHARACTERIZATION OF SURFACE-PROPERTIES OF PLASMA-POLYMERIZED FLUORINATED HYDROCARBON LAYERS - SURFACE STABILITY AS A REQUIREMENT FOR PERMANENT WATER REPELLENCY

Plasma polymers were deposited on poly (ethylene terephthalate) (PET) substrates using fluorocarbons such as CF4, C2F6, C3F6, C4F8, and mixtures thereof with CH4. The fluorocarbons selected were of saturated structure (CF4, C2F6), unsaturated structure (C3F6), and cyclic structure (C4F8). The addition of CH4 to any of the fluorocarbons caused a deposition of plasma polymers. However, the deposition rate strongly depended on the amount of CH4 added. A fluorocarbon-dominated feed, i.e., fluorocarbons with 17 mol % CH4, was found to lead to an effective deposition of plasma polymers, whereas a CH4-rich feed, i.e., fluorocarbons with 67 mol % CH4, led to an ineffective polymer deposition. For the same molar composition of fluorocarbon/CH4, polymer deposition depended on the fluorocarbon structure. It decreases in the order C3F6 > C4F8 > C2F6 > CF4. Elemental analysis showed an atomic ratio F/C of 2.2 and 2.3 for C3F6 and C4F8 plasma polymer powder, respectively, whereas the corresponding values obtained from X-ray photoelectron spectra (XPS) surface analysis of films showed 1.5 and 1.6, respectively. An explanation could lie in bulk and surface differences of the deposited layers. Contact-angle measurements revealed that among the monomers employed only C3F6 with 17 mol % CH4 resulted in a relatively stable, hydrophobic surface.