XPS ANALYSIS OF POLYPROPYLENE GRAFTED WITH ACRYLIC-MONOMERS

X-ray photoelectron spectroscopy (XPS) has been used to characterize t he surface of nonwoven polypropylene grafted with acrylic monomers. Re sults obtained for the non-ionic hydroxyethyl methacrylate (HEMA) and 2,3-dihydroxypropyl methacrylate (DHPMA) are very clear and in agreeme nt with those of CWST (critical wetting surface tension) measurements. Estimation of the thickness of the grafted layer from the XPS measure ments is consistent with results from a simple theoretical calculation . The results obtained for the ionic methacrylic acid (MAA) deviate an d are not in agreement with those of the CWST measurements. This is no t understood, but might be attributed to the folding of the more polar MAA chains under dry conditions, leading to incomplete coverage of th e surface. A second explanation is a higher contribution of grafting i n the bulk of the polymer. Both explanations are supported by grafting of MAA from methanol as solvent.