Fluorinated Ethylene Propylene Coatings Deposited by a Spray Process: Mechanical Properties, Scratch and Wear Behavior

Abstract

To increase the lifetime of metallic molds and protect their surface from wear, a fluorinated ethylene propylene (FEP) polymer was coated onto a stainless-steel (SS304) substrate, using an air spray process followed by a heat treatment. The microstructural properties of the coating were studied using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) as well as X-ray diffraction. The mechanical properties and adhesion behavior were analyzed via a nanoindentation test and progressive scratching. According to the results, the FEP coating had a smooth and dense microstructure. The mechanical properties of the coatings, i.e., the hardness and Young’s modulus, were 57 ± 2.35 and 1.56 ± 0.07 GPa, respectively. During scratching, successive delamination stages (initiation, expansion, and propagation) were noticed, and the measured critical loads LC1 (3.36 N), LC2 (6.2 N), and LC3 (7.6 N) indicated a high adhesion of the FEP coating to SS304. The detailed wear behavior and related damage mechanisms of the FEP coating were investigated employing a multi-pass scratch test and SEM in various sliding conditions. It was found that the wear volume increased with an increase in applied load and sliding velocity. Moreover, the FEP coating revealed a low friction coefficient (around 0.13) and a low wear coefficient (3.1 × 10−4 mm3 N m−1). The investigation of the damage mechanisms of the FEP coating showed a viscoelastic plastic deformation related to FEP ductility. Finally, the coating’s resistance to corrosion was examined using electrochemical measurements in a 3.5 wt% NaCl solution. The coating was found to provide satisfactory corrosion protection to the SS304 substrate, as no corrosion was observed after 60 days of immersion.

Enhancing the Output of Liquid–Solid Triboelectric Nanogenerators through Surface Roughness Optimization

“…A fluorinated ethylene propylene (FEP) film is chosen as the solid triboelectric layer due to its excellent chemical stability, outstanding radiation resistance, and superior hydrophobic, electrical, and mechanical properties (Note S1). , Figure b illustrates our process. The sandpaper is positioned on the bottom surface, and a vertical downward force is applied to the FEP film to ensure friction between the two.…”

Analysis of Wear Phenomena Produced by Erosion with Abrasive Particles against Fluoropolymeric Coatings

“…The appearance to the naked eye and that shown in the 2D images obtained show the well-differentiated aspect and particular morphological characteristics of each of these coatings. In one case, the appearance of a fairly uniform sheet can be seen, as is the case of PFA and FEP, and for PTFE, the appearance is more heterogeneous with a background that shows glosses and structures that reflect the metallic fillers that were included to improve the properties in these coatings [ 10 ].…”

“…These three fluoropolymers and their combination show extraordinary properties, which are summarized as an extreme chemical inertness [ 6 ] coupled with very low surface energy [ 7 ] and, therefore, non-stick properties [ 8 ], excellent electrical isolation [ 9 ], and high durability over a wide service temperature range. So, the correct selection is a determinant in terms of efficiency and eco-sustainability during its useful life cycle [ 10 ].…”

“…In both cases, the coating is applied by spraying or wetting, in the case of liquid resins, and via spraying or a fluidized bed in the case of powder application. Once the coating has been applied, the pieces must be polymerized in an oven between 350 and 380 °C and the fluoropolymeric layers can reach thicknesses between 40 and 125 μm [ 10 ].…”

Rheology and Processing of Polymers

“…Najoua Barhoumi et al [2] designed a sort of fluorinated ethylene propylene (FEP) polymer coating with the aim of protecting the stainless-steel (SS304) mold substrate surface from corrosion and wear. Through an air spray process and curing, a compact and uniform film was obtained, and the mechanical, adhesion and corrosion, etc., properties were tested.…”