This group demonstrated that PTFE strongly adhered to rubber even if thermocompression was performed to PTFE one year after plasma treatment, verifying that the lifetime of surface modification was very long. It was confirmed that the wettability to water of PTFE treated with heat-assisted plasma treatment didn’t change a year after the treatment and that 80 percent or more of peroxide radicals produced by plasma treatment remained a year after the treatment.

This group’s achievement has eliminated the need to adhere in a rush after plasma treatment, drastically easing restrictions on the adhesion process. Heat-assisted plasma treatment has made it possible to keep the adhesion strength of PTFE. This will allow companies without plasma treatment devices to use PTFE with excellent adhesion and lead to the expansion of applications of PTFE. Applications to resin other than PTFE will also be discussed in the future.

Abstract

A polytetrafluoroethylene (PTFE) surface was modified using atmospheric pressure plasma treatment under heating (heat-assisted plasma treatment) to promote its direct adhesion to isobutylene–isoprene rubber (IIR) without any adhesives. Plasma-treated PTFE and unvulcanised IIR were thermally compressed and their adhesion strength was evaluated via a T-peel test. Heat-assisted plasma treatments conducted above 250 °C drastically increased the adhesion strength over 2.0 N mm ⁻¹ before IIR failure. The plasma-treated PTFE surface was evaluated using X-ray photoelectron spectroscopy, nanoindentation and scanning electron microscopy. The results of these analyses indicated that the adhesion strength drastically increased because heat-assisted plasma treatment promoted the formation of carbon–carbon crosslinks and/or etching of a weak boundary layer (WBL) on the PTFE surface. This led to the recovery of the WBL in PTFE, which resulted in the prevention of PTFE inter-layer peeling in the WBL. In addition, the estimated lifetime of the surface modification surprisingly exceeded one year.

Figire 1. Long lifetime of high adhesion property of heat-assisted plasma-treated PTFE. White: fluoropolymer sheet, Blue: isobutylene–isoprene rubber (IIR).

To learn more about this research, please view the full research report entitled “ Adhesive-free adhesion between polytetrafluoroethylene (PTFE) and isobutylene–isoprene rubber (IIR) via heat-assisted plasma treatment ” at this page of the RSC Advances website.