R. Foerch et al., PLASMA SURFACE MODIFICATION OF POLYETHYLENE - SHORT-TERM VS LONG-TERMPLASMA TREATMENT, Journal of adhesion science and technology, 7(10), 1993, pp. 1077-1089
A remote plasma reactor, with air as the plasma gas, has been used for
in-line surface modification of linear low-density polyethylene tape
(LLDPE) passing 10 cm below the main plasma zone. Line speeds of up to
0.70 m/s were tested, allowing the study of 0.014 s exposure times to
the plasma. Oxygen to carbon (O/C) ratios averaging 0.11 were observe
d on a reproducible basis. The reactor was also used for static plasma
treatment under similar experimental conditions. This allowed a compa
rative study of short-term (milliseconds) vs. long-term (several secon
ds) plasma treatment. High-resolution X-ray photoelectron spectroscopy
(XPS) analysis of the treated polymer surface suggested the formation
of hydroxyl (C-OH), carbonyl(C=O) and carboxyl (O-C=O) groups, even a
fter short plasma treatment. The intensities of these components were
seen to increase in approximately equal quantities with increasing O/C
ratio. Water washing of polyethylene surfaces with high O/C ratios sh
owed a loss of oxygen, apparent as a decrease in O-C=O groups in the C
ls spectra. A smaller loss in oxygen was observed when washing sample
s that had been plasma-treated for milliseconds. A surface ageing stud
y revealed that polyethylene surfaces that had been plasma-treated for
short time periods showed only a negligible loss of oxygen on prolong
ed exposure to air. Surfaces treated for longer time periods showed a
loss of up to 50% of the total oxygen on the surface within a few days
of treatment. Static secondary ion mass spectrometry has provided som
e supporting evidence for surface damage of the treated films.