Surface properties,Df a Melinex 800 PET polymer material modified by an atin ospheric-pres sure air dielectric barrier discharge (DBD) have been studied using X-ray photoelectron microscopy (XPS) and contact angle measurement. The results show that the material surface treated by the DBD was modified significantly in chemical composition, with the highly oxidised carbon species increasing as the surface processing proceeds. The surface hydrophiLcity was dramatically improved after the treatment, with the surface contact angle reduced from 81.8 degrees for the as-supplied sample to lower than 50 degrees after treatment. Post-treatment recovery effect is found after the treated samples were stored in air for a long period of time, with the ultimate contact angles, as measured, being stabilised in the range 58-69 degrees after the storage, varying with the DBD-treatment power density. A great amount of the C-O type bonding formed during the DBD treatment was found to be converted into the C=O type during posttreatment storage. A possible mechanism for this bond conversion has been suggested. (c) 2006 Elsevier B.V. All rights reserved.