Atmospheric pressure plasmas provide a fast and effective method for treating polymer surfaces prior to adhesive bonding. In this work, Polymethyl-methacrylate (PMMA) and Polyetheretherketone (PEEK) were activated with an atmospheric plasma having a 2” wide beam and operated with 30 L/min helium, 1.5 L/min oxygen, and ~200 W radio frequency power. The water contact angle on the PMMA dropped from 75° to 45° after a 20 ms exposure to the plasma, whereas the water contact angle on the PEEK composite dropped from 65° to 20° after a 10 s exposure. Following treatment, adhesive film was applied to the polymer samples and a series of lap shear tests (ASTM D-3165) were performed. In each case, cohesive failure within the glue was observed. For the PEEK samples, average lap shear strengths of 43.2±0.6 MPa were obtained using 3M AF-563 film adhesive. This shear strength was roughly ten times greater than that obtained without plasma treatment. Environmental testing revealed that the plasma-exposed composite surfaces could sit for at least 8 hours at 49 °C and 90% relative humidity prior to applying the adhesive with no loss of bond strength. The surfaces of the PMMA and PEEK polymers have been characterized before and after atmospheric plasma treatment by x-ray photoemission spectroscopy, infrared spectroscopy, and scanning electron microscopy. At the meeting we will describe the chemical mechanisms responsible for the changes in the properties of the polymer surfaces.

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