The Effect of Pulse Ultraviolet Laser Modification on the Surface Wetting Property of Polycarbonate

The effect of the etching and modification power density of 355 nm pulse (100 kHz) ultraviolet (UV) laser on the wetting property of the surface of polycarbonate (PC) materials was found to have the following regularity: when the laser power density was less than 0.27×10 8 W/cm 2 , a hydrophilic surface of PC was produced; While the laser power density was from 1.15×10 8 W/cm2 to 10×10 8 W/cm2, a hydrophobic surface could be obtained. The mechanism of the effect of UV laser etching and modification on the wetting property of PC surface was explored in detail by Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). It was shown that, when laser power density was larger than 1.15×10 8 W/cm2 , the polar groups containing element oxygen on the surface of the modified PC increased. However, the porous microstructure with V type-groove resulted from the laser etching and modification determined the hydrophobicity of the PC surface. The distinct microstructure was able to result in the composite contact of water droplet on the PC surface. When certain laser power density was used to modify the PC surface, the feasibility to explain the changes of the water contact angle and wetting property of PC surface with Cassie model was also investigated.