Laser irradiation effects on polyethylene sheets containing carbon nanotubes

Ultra high molecular weight polyethylene was chemically mixed with multiwall carbon nanotubes (CNT) and irradiated with pulsed visible laser (532 nm wavelength, 170 mJ pulse energy, 10 Hz repetition rate) for different times. Physical and mechanical characterization analyses were performed before and after the laser irradiation. CNT presence increases the polymeric hardness and the surface wet ability. Laser irradiation modifies a thin surface layer, of the order of 100-200 mu m depth. Absorption coefficient in CNTs (similar to 2 x 10(4) cm(-1)) is higher compared with that of polyethylene (similar to 150 cm(-1)) and absorbed energy generates fusion and removing of nanotubes. The final nanocomposite surface properties changes becoming similar to that of pure polyethylene, while the bulk properties remain unchanged. Generally, laser irradiation changes the nanocomposite wet ability, decreases its hardness, increasing its roughness. At low irradiation doses nanotubes are broken and detached from surface inducing voids and discontinuities. At high doses the surface appears more and more compact and rich in polyethylene.