Adhesion enhancement of polymer surfaces by atmospheric plasmatreatment

Abstract

An atmospheric pressure non-equilibrium plasma (APNEP) developedin the UK by EA Technology Ltd is currently being investigated incollaboration with the University of Surrey. Of the many applications ofsurface modification that can be induced using plasmas, adhesionenhancement is one of the most commercially important. In this paper, weillustrate the use of an atmospheric plasma to enhance the adhesioncharacteristics of low-density polyethylene (LDPE) and poly(ethyleneterephthalate) (PET). The polymers were treated in the remote afterglowregion of an atmospheric pressure plasma to avoid the thermal effects thatcan cause degradation for thermally sensitive materials when placed indirect contact with the plasma. Reactive (oxygen containing) and inert(oxygen free) atmospheric plasmas rapidly impart adhesion enhancement by afactor of two to ten as measured by 180° peel tests. However,extended exposure to the atmospheric plasma does not impart additionaladhesion enhancement as the surface is ablated revealing the underlyingpolymer with poor adhesive characteristics. In contrast, vacuum plasmatreated LDPE and PET show increased adhesion with extended plasmatreatment. An adhesion enhancement in excess of two to three orders ofmagnitude was found to be achievable for vacuum plasma treatment timesgreater than 10 min.