Ultra High molecular weight polyethylene(UHMWPE) films were photooxidized by UV/ozone irradiation. Reflectance of the irradiated films decreased in the low wavelength regions of visible light, indicating destructive interference of visible light due to roughened surface. The UV treatment developed the nano-scale roughness on the UHMWPE films surface, which increased by twofold from 82.6 to 156.6nm in terms of peak-valley roughness. The UV irradiation caused the oxygen content of the UHMWPE film surface to increase. Water contact angle decreased from 83.2 o to 72.9 o and surface energy increased from 37.8 to 42.6mJ/m 2 with increasing UV energy. The surface energy change was attributed to significant contribution of polar component rather than nonpolar component indicating surface photooxidation of UHMWPE films. The increased dyeability to cationic dyes may be due to the photochemically introduced anionic and dipolar dyeing sites on the film surfaces.
Polyethylene(PE) films were photocrosslinked by continuous UV irradiation. Benzophenone addition as low as 1wt% into the PE film increased the gel fraction up to 96%. The photocrosslinking was attributed to the recombination of PE radicals generated upon UV irradiation, which was enhanced by the hydrogen abstraction of the added benzophenone. Also the crossliked PE showed higher thermal stability and decreased crystallinity with increasing UV energy as shown by TGA, XRD and DSC analysis. It was also possible to fix 5.4% octadecane into PE by the photocrosslinking. The crosslinked PE film containing octadecane showed lower tensile strength and modulus coupled with higher extension compared to that without octadecane, which can be used as a new plasticizing method for the crosslinked PE film.
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