A Comparative Study of Chop-wave and Superpulse CO2 Laser Surface Modification of Polyurethane

The present study was undertaken to evaluate and compare the effects of chopwave (CPW) and superpulse wave (SPW) of CO2 laser on polyurethane. The results showed that at the threshold fluences of 200 and 400 mJcm-2 for CPW and SPW, the final temperatures would be about 322 and 343 K justified by their effective absorption coefficients of ≈1.2 × 103cm-1 and 1.3 × 103cm-1, respectively. These values are well below the minimum melting temperature (≈393 K) of polymer. The ATR-FTIR spectral analysis showed four new peaks at 1436, 1370, 1259 and 958 cm-1 after laser irradiation indicative of increased hydrogen bonding. The best surface free energy of 50 mNm-1 was obtained after 8 pulses of CPW which corresponds to a contact angle of 75. Topological studies using SEM evaluation illustrated that a smooth wall crater can be produced by SPW and CPW at higher laser pulse numbers and relatively low input power. Finally, in ourexperiments the highest value of surface free energy was achieved by CPW mode at 0.1 W after 8 pulses. Although, SPW produced a narrower zone of thermal degradation, surface free energy of polymer, however was found to be weaker than CPW mode.