THE EFFECT OF SURFACE FLUORINATION ON THE WETTABILITY OF HIGH-DENSITYPOLYETHYLENE

High-density polyethylene (HDPE) samples have been fluorinated and oxy fluorinated for different times. Dynamic contact angle analysis was us ed to determine the effect of fluorine gas mixtures on the surface of HDPE. The total surface tension of HDPE increased drastically with the length of oxyfluorination treatment, but levelled off after longer tr eatments. Fluorination resulted in a marked decrease in the total surf ace tension of HDPE. During fluorination, the dispersive component of the surface tension decreased progressively with fluorination time, wh ile the polar component increased initially but decreased again with l onger fluorination treatments. This indicates that short fluorination times lead to increased wettability by polar liquids, while longer flu orination times have the opposite effect. Fluorinated and oxyfluorinat ed surfaces were exposed to elevated temperatures. Whereas it was foun d that fluorinated surfaces changed measurably, oxyfluorinated surface s changed dramatically upon heating at 100 degrees C. Photoacoustic FT -IR spectroscopy indicated that this was probably due to migration of surface polar groups into the bulk of the polymer, rather than chemica l change.