Polypropylene(PP) was treated by an oxygen capacitively coupled radio frequency plasma(CCP) under a radio frequency(RF) power of 200 W for exposure time of 1,5,and 10 min.The ageing process of the plasmatreated PP was studied at an ageing temperature of 90 ℃ during an ageing time up to 25 h.The formation of the nanotextures with different geometry and aspect ratio and the grafting of large number of oxygencontaining groups were achieved on as-treated PP surfaces under the oxygen CCP treatment for the increased exposure time.The hydrophilicity on the as-treated PP surfaces with the stable nanotextures was rapidly depressed during the ageing process at 90 ℃ due to the restructuring of chemical composition.The surface restructuring rate was dependent on the aspect ratio and the oxygen-containing groups on the nanotextured PP with increasing exposure time.The hydrophobic over-recovery to high hydrophobicity and superhydrophobicity were observed on the post-aged surfaces with the stable nanofibrils from as-treated hydrophilic surfaces.The superhydrophobicity with the low water adhesion was achieved on the post-aged surfaces preserving the nanofibrils with high aspect ratio and large distance due to the decrease of the oxygen-containing groups after the surface restructuring.
