SURFACE AND INTERFACE ANALYSIS Surf. Interface Anal. 29, 729–734 (2000) ESCA characterization of fluoropolymer film residue on carbon-fiber-reinforced plastic components Jesse T. Cherian 1 * and David G. Castner 2 1 Northwest Surface Laboratory, 4208 South 252nd Place, Kent, WA 98032, USA 2 Department of Chemical Engineering, Box 351750, University of Washington, Seattle, WA 98195, USA High-performance aerospace composite manufacturing of carbon-fiber-reinforced plastic (CFRP) compo- nents makes use of release films during standard cure processes. After removal of a release film, unwanted residue from the film has been known to decrease the bond strength of adhesive joints in CFRP parts. Electron spectroscopy for chemical analysis (ESCA) has been used as a relatively non-destructive surface analysis technique to determine the atomic composition and chemical species present on the CFRP surfaces. The identification of the chemical species present on the surface can lead to a better understanding of the overall bond structure and functional composition of the elements in a given surface, distinct from the bulk chemistry of the substrate. In this study, ESCA analyses were done on CFRP surfaces prepared with two dif- ferent fluoropolymer release films: fluorinated ethylene–propylene (FEP) and ethylene–tetrafluoroethylene (ETFE). Differences in the high-resolution spectra were used to determine the amount of fluoropolymer transferred to the CFRP surface after removal of the release films. The ESCA quantification showed that FEP release films transferred less material than ETFE release films to the surface of the cured CFRPs. Copyright  2000 John Wiley & Sons, Ltd. KEYWORDS: surface analysis; ESCA; bonding; FEP; ETFE; CFRP; XPS INTRODUCTION Composite engineers require analytical information regarding the surface composition and chemistry of the surfaces that they work with. The quality and integrity of a bonded joint can be correlated to this surface chemistry. During the fabrication of carbon-fiber-reinforced plastic (CFRP) components, uncured composite plys (prepregs) are assembled or laid-up onto tooling molds. These molds are typically coated with a release agent to enable the cured composite to separate easily from the tool surface. Release films or plys are also used in lieu of release agents in certain steps of the composite manufacturing process. 1 These release plys are by nature slippery or non-adhesive and are designed to be able to be removed easily, even after a curing cycle. A potential problem arises when the release ply leaves behind a residue that may prove detrimental to a subsequent bonding process. This contamination by the residue from the release ply can result in loss of adhesion and bond strength of cured composite structures. 2–3 Locating and identifying these contaminants often require sensitive surface analysis techniques. Surface analysis techniques such as electron spec- troscopy for chemical analysis (ESCA) can quantita- tively detect extremely thin layers of surface contaminants * Correspondence to: J. T. Cherian, Northwest Surface Laboratory, 4208 South 252nd Place, Kent, WA 98032, USA. E-mail: nwsl@gte.net that are not detectable by non-surface-sensitive analytical techniques. 4 Industries such as aircraft, automotive, elec- tronic, plastics and paint have routinely used ESCA to characterize their products and processes. 5,6 In this exam- ple, ESCA is shown to identify marker elements and cor- responding binding energy shifts that provide invaluable qualitative and quantitative engineering data. EXPERIMENTAL Electron spectroscopy for chemical analysis The two instruments used in this study were M-Probe spectrometers made by Surface Science Instruments at Boeing Materials Technology’s Surface Characterization Laboratory and the University of Washington’s Sur- face Analysis Recharge Center. Monochromatic Al K˛ (1486.6 eV) x-rays were used to generate the ESCA spec- tra. A nominal analyzer pass energy of 150 eV was used to acquire wide-scan spectra for determining the elemental surface composition of the samples. A lower pass energy of 25 eV was used to acquire the high-resolution spectra for determining the binding energy positions of specific functional groups. Each sample analyzed was electrically non-conductive. This required using a flood gun to con- trol charge build-up from the excess secondary electrons generated by the x-ray flux. The flood gun was set at a nominal voltage of 4.0 V and the binding energy scale was referenced by setting the hydrocarbon peak to 285.0 eV. Copyright  2000 John Wiley & Sons, Ltd. Received 14 July 1999 Revised 7 July 2000; Accepted 7 July 2000