The effect of CH4/H2 ratio on the surface properties of HDPE treated by CHx ion beam bombardment

The surface of high density polyethylene (HDPE) substrate was bombarded by the CHx group ion beam, which was generated by the mixture of CH4/H-2. Varying the CH4/H-2 ratio, HDPE surfaces with different chemical bond structures and properties were obtained. Raman and XPS results show that sp(2) and sp(3) bond structures are formed at HDPE surface bombarded by CHx group ions. The sp(3) bond fraction at bombarded HDPE surface depends on the H-2 ratio in CH4/H-2 mixture, because the H ion/atom/molecule can improve the growth of sp(3) bond structure. For HDPE surface bombarded by CH4/H-2 = 50/50, sp(3) bond fraction reaches the maximum of 30.5%, the surface roughness decreases to 17.04 nm, and the static contact angle of polar H2O molecule increased to 140.2 degrees.