The surface functionalisation of polyethylene and polypropylene by industrial and
laboratory scale corona treatments and by laboratory flame treatment was studied. The
surface sensitive techniques of X-ray photoelectron spectroscopy (XPS), attenuated total
reflection infra-red spectroscopy (FTIR-ATR), contact angle measurement and electron
microscopy (SEM and TEM) were employed. Corona and flame treatments resulted in
incorporation of oxygen only into the surfaces of both polyethylene and polypropylene,
resulting in improved surface wettabilities. A variety of oxygen functional groups were
introduced by the two treatments. The industrial and laboratory scale treatments of both
polymers were found to be similar in terms of the oxygen concentrations incorporated and
surface wettabilities achieved. The presence of significant amounts of chain scission
products were indicated on corona treated surfaces, while only minimal quantities were
indicted on flame treated surfaces. This was attributed to their volatilisation during flame
treatment. Introduction of sulfur dioxide into the flame and corona regions during
treatment resulted in significant improvements in surface wettability. Incorporation of
sulfur and nitrogen resulted from the presence of sulfur dioxide. A possible mechanism
involving the formation of sulfonic acid groups and ammonium sulfonate groups was
suggested. An oxidation depth model developed for use with variable take-off angle XPS
showed that significantly deeper oxidation occurred in the presence of sulfur dioxide.
Corona treatment was more effective in improving surface wettabilities than flame
treatment, this being attributed to heat induced functional group reorientation during flame .
treatment for polyethylene and to differences in surface chemistry resulting from the two
treatments in the case of polypropylene. The surface wettability of poly ethylene was more
readily improved than the surface wettability of polypropylene after all the treatments
investigated. A method for estimating functional group concentrations using chemical
derivatisation and contact angle measurement was developed. Functional group estimates
for flame treated polyethylene were found to be in good agreement with chemical
derivatisation used in conjunction with XPS measurements.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.