Thickness Effects of Surface Direct Fluorination and Plasma Modification on Ultra-High Molecular Weight Polyethylene Ultrathin Membranes

For the first time, an ultrathin type of ultra-high molecular weight polyethylene (UHMWPE) membrane of only 350 nm thickness is surface modified by direct fluorination and plasma treatments. Then a notable suppression in crystallinity is observed. A total of four kinds of thickness, from 350 nm to 6 mu m, are investigated to correlate the modification effect on the thickness. Microscopically, the continuous shish-kebab structure transforms into scattered lamellae clusters. And the damage to the surface morphologies increases as the thickness decreases, yet the resultant contact angles remain almost constant. Especially for the 350 nm thin UHMWPE, the mildest fluorination treatment slightly changes the contact angle, while the multiscale structure changes significantly from crystalline to mesoscopic level. As thickness decreases from 6 mu m to 350 nm, the modified volume ratio of membranes increases, and the volumetric modification is almost realized for the 350 nm membrane.