Plasma-pretreated Poly Tetrafluoroethylene Films Research Articles

Studies on the adhesion between polytetra‐fluoroethylene film and silanized glass foil

AbstractAdhesion of plasma‐pretreated polytetrafluoroethylene (PTFE) films to glass foils silanized with 3‐aminopropyltriethoxysilane (APS) was demonstrated via thermally induced surface graft polymerization with concurrent lamination. The simultaneous thermal grafting and lamination process was carried out under atmospheric conditions in the presence of pure acrylic acid (AAc) or aqueous solutions of acrylamide (AAm) and in the absence of polymerization initiator. The chemical composition and microstructure of the modified PTFE films and glass foils were characterized by XPS. The effects of the plasma pretreatment time for the substrates, thermal grafting/lamination temperature and time and graft monomers on the adhesion strength of the PTFE/APS‐glass junction were studied. The adhesion strengths of PTFE/APS‐glass assemblies were significantly improved in the presence of AAc or AAm. The 180° peel adhesion strength of the PTFE/AAc/APS‐glass and the PTFE/AAm/APS‐glass assemblies can reach about 11.2 and 4.6 N cm−1, respectively. Analysis of the mechanically delaminated surfaces by XPS suggests that the failure modes of both assemblies involve mainly the cohesive failure in the PTFE substrate and some very small adhesion failure in the graft layer. Copyright © 2004 John Wiley & Sons, Ltd.

Lamination of polytetrafluoroethylene films via surface thermal graft copolymerization with ionic and zwitterionic monomers

Surface thermal graft copolymerization with concurrent lamination was carried out between two argon plasma-pretreated polytetrafluoroethylene (PTFE) films in the presence of aqueous zwitterionic solutions of N,N-dimethyl-N-methacrylamidopropyl-N-(3-sulfopropyl)ammonium betain (DMASAB), N,N-dimethyl(methacryloylethyl)ammonium propansulfonate (DMAPS), and 1-(3-sulfopropyl)-2-vinylpyridinium betaine (SVPB), as well as an aqueous ionic solution of potassium-2-sulfopropylacrylate (SPA) and potassium-2-sulfopropyl methacrylate (SPM), under atmospheric conditions and in the complete absence of an added initiator and system degassing. The lap shear adhesion strength between the PTFE films from simultaneous grafting and lamination depended on the argon plasma pretreatment time of PTFE films, the thermal lamination temperature, the concentration of the monomer solution, and the ionic nature of the grafted chains. Lap shear adhesion strength greater than 120 N/cm2 and exceeding the yield strength of the PTFE substrate used could be readily obtained in most PTFE/zwitterion/PTFE assemblies after simultaneous thermal graft copolymerization and lamination. The chemical compositions of the graft-copolymerized surfaces were studied by X-ray photoelectron spectroscopy (XPS). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 816–824, 1999

Surface modification of polytetrafluoroethylene filmsvia graft copolymerization for auto-adhesion

The surfaces of Ar plasma-pretreated polytetrafluoroethylene (PTFE) films are further functionalized via UV-induced graft copolymerization with amphoteric N,N′-dimethyl(methacryloylethyl)ammonium propansulfonate (DMAPS) either in Ar atmosphere, or under atmospheric conditions and in the absence of a polymerization initiator. The so-modified PTFE films from either process are capable of exhibiting adhesive-free adhesion or auto-adhesion with one another when brought into intimate contact in the presence of a small quantity of water. The lap shear adhesion strength increases with increasing graft concentration and can readily exceed the yield strength of the PTFE substrate. Two plasma-pretreated PTFE films also readily undergo thermal graft copolymerization with concurrent lamination when lapped together in the presence of a small quantity of the DMAPS monomer solution at elevated temperature in the atmosphere. The surface compositions of the graft-copolymerized PTFE films and the delaminated surfaces were characterized by X-ray photoelectron spectroscopy (XPS). In most cases, adhesional failure occurred near the graft-substrate interphase. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3107–3114, 1998

Surface Modification and Functionalization of Polytetrafluoroethylene Films

Argon plasma-pretreated polytetrafluoroethylene (PTFE) films were subjected to further surface modification by near-UV light-induced graft copolymerization with acrylic acid (AAc), sodium salt of styrenesulfonic acid (NaSS), and N,N-dimethylacrylamide (DMAA). The surface compositions and microstructures of the modified films were characterized by angle-resolved X-ray photoelectron spectroscopy (XPS). A stratified surface microstructure with a significantly higher substrate-to-graft chain ratio in the top surface layer than in the subsurface layer was always obtained for PTFE surface with a substantial amount of the hydrophilic graft. The stratified surface microstructure was consistent with the observed hysteresis in advancing and receding water contact angles. The graft yield increased with Ar plasma pretreatment time and monomer concentration. Covalent immobilization of trypsin on the AAc polymer-grafted PTFE films was facilitated by water-soluble carbodiimide (WSC). The effective enzyme activities increased initially with increasing surface concentration of the grafted AAc polymer but became saturated at a moderate AAc polymer concentration. The immobilized enzyme could still retain close to 30% of its original activity. Solution-coating of the polymeric acid-modified PTFE films with the emeraldine (EM) base of polyaniline readily resulted in an interfacial charge transfer interaction and a semiconductive PTFE surface.