XPS and surface resistivity measurements of plasma-treated LDPE and ageing effects

Low-density polyethylene (LDPE) film containing a polydimethylsiloxane (PDMS) additive has been investigated using x-ray photoelectron spectroscopy (XPS) and surface resistivity measurements. The samples measured were: as-received; plasma-treated; washed with ethyl acetate; aged in air; and combinations of these treatments. Analysis by XPS has been used to characterize surface species concurrently with resistivity in the surface region to assist in understanding the relationship between charge transport and surface electronic structure. Radiofrequency plasma treatment causes major oxidation effects and lowering of resistivity in the first 4 s. With the same treatment time, in the case of washed samples, surface segregation of PDMS is enhanced, causing an initial increase of surface region resistivity. Plasma treatment beyond 4 s causes saturation of the O:C ratio in the surface and a loss of charged bonds. These points also allow a description of resistivity change with ageing, which includes hydration e ffects on exposure to air.