LASER-INDUCED ADHESION ENHANCEMENT OF POLYMER COMPOSITES AND METAL-ALLOYS

Proper surface treatment of an adherend is among the decisive factors concerning the final quality and durability of an adhesive joint. Vari ous surface treatments are applied to plastic and metal adherends; amo ng them are abrasive treatment, chemical treatment, and plasma etching . An alternative method is presented here which utilizes an excimer UV laser as a new technique for preadhesion surface treatment. Experimen tal results indicated that preadhesion laser surface treatment improve d significantly the shear strength of adhesively bonded aluminum joint s as compared with untreated or anodized substrates. Laser treatment a lso improved the adhesion strength of polycarbonate, polyetherimide, a nd composite adherends as compared with untreated or simply abraded su bstrates. Optimal laser treatment parameters (intensity, repetition ra te, and number of pulses) depend on the substrate material and its che mical nature. As a result of laser treatment, the mode of failure chan ged from interfacial to cohesive as long as ablation did not occur. Th e adhesion enhancement resulted from morphological changes of the adhe rend surface caused by the laser irradiation as revealed by SEM (scann ing electron microscopy), and from chemical modification and surface c leaning as indicated by ESCA (electron spectroscopy for chemical analy sis) and FTIR (Fourier transform infrared spectroscopy). It can be con cluded that the excimer laser has potential as a precise, clean, ecolo gically favorable, and simple preadhesion treatment for a wide variety of materials.