Reaction of argon plasma‐treated teflon PFA with aminopropyltriethoxysilane in its n‐hexane solution

Abstract

Aspects of argon plasma treatment of tetrafluoroethylene–perfluoropropylvinylether copolymer (PFA) films, followed by air exposure and its subsequent reaction with 3-aminopropyltriethoxy silane (3-APS) have been investigated using XPS and electron spin resonance (ESR) to gain a better understanding about the surface bonding between the modified PFA and 3-APS. The plasma treatment was performed under varying parameters such as radiofrequency power, gas pressure and treatment time. A good correlation was found between the atomic ratios of O/F and Si/F for PFA before and after the reaction with 3-APS. The amount of peroxy radicals before the reaction with 3-APS was also closely related with the atomic ratio of Si/F. By the derivatization reaction of plasma-treated PFA with NaOH it was confirmed that C(O)OH groups exist on the treated PFA surfaces. These observations revealed that the oxygen incorporated at the surface leading to C(O)OH groups plays a substantial role as the reaction site for 3-APS. A similar trend was found between the atomic ratios of Na/F and Si/F after the reactions with NaOH and 3-APS. Based on this observation it is proposed that the surface bonding of 3-APS to the C(O)OH group at the surface occurs through its NH2 group. The analysis of the atomic ratios of O/F, N/F and Si/F after the reaction with 3-APS revealed that a polyaminosiloxane oligomer with a stoichiometry different from that expected for the original 3-APS is formed. The wettability of 3-APS-bound PFA was found to become much greater than that of PFA plasma treated alone. The ageing effect of the wettability of 3-APS-bound PFA was observed, whereas the Si atomic concentration at the surface remained nearly unchanged during ageing. Copyright © 1999 John Wiley & Sons, Ltd.