Adhesion Improvement of Thermoplastics-Based Composites by Atmospheric Plasma and UV Treatments

Abstract

The present work is concerned with adhesive bonding of thermoplastic composites used in general aerospace applications, including polyphenylene sulfide (PPS), polyetherimide (PEI) and polyetheretherketone (PEEK) carbon fibre composites. Three different surface treatments have been applied to the PEEK, PPS and PEI-based composites in order to enhance the adhesion: atmospheric plasma, ultraviolet radiation (UV) and isopropanol wiping as a control. Water contact angles and free surface energies were measured following the standard experimental procedure based on the employment of three different liquid droplets. Infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) were subsequently performed to characterize the surface chemistry of the samples after treatment. The single lap joints were manufactured and bonded by an Aerospace grade epoxy-based film adhesive originally developed for use on metals but with the ability to bond treated thermoplastics to good strength (supplied by Henkel Ireland). Quasi-static (QS) tests were conducted. The lap shear strength was evaluated, and the failure mechanisms of the different joints were examined for the range of surface treatments considered. It was found that the performances of the PEEK and PPS joints were considerably improved by the plasma and UV treatments resulting in cohesive and delamination failures, while PEI was unaffected by the plasma and UV treatments and performed very well throughout.

Quasi-static perforation response of inter-ply hybrid polypropylene composites at various temperatures

“…8 In this regard, thermoplastic composites (TPCs) possess a great potential with superior mechanical strength, 9 formability, 10 and fabrication advantages. 11…”

Evaluation of polyphenylene sulfide by surface thermodynamics approaches: Comparison with common polymers

“…These results are in good agreement with the previous literature reports. For example, Scarcelli et al 6 reported θ water = 95 , Luo et al 42 reported θ water = 96 , and we measured 96 ± 1 W contact angle for the PPS surface. Similarly, Wang et al 9 reported θ glycerol = 80 ± 2.1 , and we found 80 ± 2 GLY contact angle in our experiments.…”

“…For example, Scarselli et al treated the PPS surface with atmospheric plasma and UV lamp to increase the SFE of the PPS, and obtained improved lap shear strength properties as a result of this treatment. 6 Lv et al obtained a corrosionresistance superhydrophobic PPS surface by introducing the silicone rubber particles and carbon nanotubes into PPS matrix. 7 The same group converted the PPS surface to a superhydrophobic surface using amino silicon oil as a low SFE material.…”

Enhancement of metal adhesion, owing to the plasma texturing of PEEK

“…The increased roughness can be easily obtained at a reduced cost by mechanical abrasion (grinding, sanding, or sandblasting) but may be relatively ineffective and hard to control. [ 3,4 ] Chemical methods are also described, such as acid etching, [ 5 ] but they are sometimes accompanied with an alteration of the physicochemistry of the surface and the etching in solution requires the use of solvents that are themselves toxic and sometimes volatile (volatile organic compound).…”