SURFACE MODIFICATION OF POLYMER-FILMS BY GRAFT-COPOLYMERIZATION FOR ADHESIVE-FREE ADHESION

The surfaces of low density polyethylene (LDPE), poly(carbonate) (PC), polytetrafluoroethylene (PTFE) and emeraldine (EM) base films of poly (aniline) are modified by graft copolymerization with N,N-dimethylacry lamide (DMAA), Na salt of styrenesulfonic acid (NaSS), 3-dimethyl(meth acryloylethyl)ammonium propanesulfonate (DMAPS) and acrylic acid (AAc) . Two surface graft copolymerized films are capable of exhibiting 'adh esive-free' adhesion or auto-adhesion when brought into contact in the presence of water and subsequently dried. The development of the lap shear adhesion strength depends upon the concentration of the surface graft, the contact adhesion (drying) time, the nature of the substrate , the microstructure of the graft copolymerized surfaces and the exten t of molecular interaction (dispersive, electrostatic, etc.) at the la pped junction. Lap shear adhesion strengths in excess of 90 N cm(-2) w ere readily achieved between films graft copolymerized with the amphot eric DMAPS, as well as between a DMAPS graft copolymerized EM film and an AAc graft copolymerized PTFE film. X-ray photoelectron spectroscop y (x.p.s.) analysis of the delaminated surfaces suggests that the fail ure mode involves the fracture of the graft chains at the substrate-gr aft interface. (C) 1998 Elsevier Science Ltd. All rights reserved.