Penetration of plasma surface modification. II. CF4 and C2F4 low-temperature cascade arc torch

The depth of surface modification by low-temperature cascade arc torch is investigated. A stack of 10 sheets of nonwoven fabrics of polyester fibers is exposed to a low-temperature cascade arc torch containing CF₄ or C₂F₄, and the fluorination effect is examined by ESCA. It is shown that interaction of chemically reactive species, created in a low-temperature cascade arc torch, with the surface is not limited to the surface contacted by the torch (flame). The results indicate that the fluorination effect is observed on surfaces which are shadowed from the torch by overlying fibers. The highest degree of fluorination is found on the second layer, rather than on the first layer which the torch contacts directly. No significant differences in the trends of penetration of CF₄ and C₂F₄ treatment through porous samples are observed. However, ESCA data show principal differences in chemical structures of the surfaces treated with CF₄ (nonpolymer-forming gas) and C₂F₄ (polymer-forming gas). These results indicate that chemically reactive species induced by the excited species of argon rather than primary species created by the ionization process seem to play predominant roles in the surface treatment as well as the low-temperature cascade arc torch polymerization of perfluorinated compounds. © 1994 John Wiley & Sons, Inc.