A Fluoropolymer Coating on Carbon Fibers Improves Their Adhesive Interaction with PTFE Matrix

Abstract

Carbon fibers were treated in a HF glow discharge in tetrafluoroethylene and octafluorocyclobutane in order to improve their adhesion to poly(tetrafluoroethylene) matrix. As the result of the plasma treatment, a thin (20-140 nm) fluoropolymer coating was deposited onto the fiber surface. The structure of this coating was studied by means of IR spectroscopy, XPS, AFM and SEM techniques. The coating material appeared to be similar to PTFE in its chemical composition but distinguished by branched, partially crosslinked, amorphous structure and included unsaturated chemical bonds. The coating thickness of 70 nm was sufficient to effectively screen the field of molecular forces of the initial substrate, thus, decreasing the surface energy of the fibers and improving their compatibility with the PTFE matrix. The adhesive strength in the PTFE-carbon fiber systems, measured by means of the microbond test, more than doubled upon the plasma treatment (the local interfacial shear strength increased from 10.7 to 29.7 MPa, apparent IFSS from 4.3 to 7.8 MPa), and the interfacial frictional stress increased by 70%. The new composite material consisting of 20% short coated carbon fibers in the PTFE matrix showed better mechanical, thermal and tribological characteristics as compared with the composite reinforced with untreated fibers.

Mechanical and Tribological Properties of Polytetrafluoroethylene Composites with Carbon Fiber and Layered Silicate Fillers

“…The mechanical properties of PCMs with fiber fillers depend on both the adhesion between the components and the properties of the interfacial layer at the polymer–fiber interface [18]. The surface of the CFs used here were modified using a plasma–chemical treatment with fluororganic compounds, which reduced the surface energy of the fibers, resulting in better wetting of the fiber surface with the PTFE, thereby, increasing their compatibility [19]. Figure 3 shows an SEM image of the PCM supramolecular structure on the fiber surfaces.…”

Development of Antifriction Materials Based on Polytetrafluoroethylene Filled with Binary Fillers

“…The results of the physico-mechanical characteristics of the initial PTFE and PCM based on it are given in Table. 1. The study employed carbon fibers of the BELUM brand modified in the medium of organofluorine compounds by plasmachemical method [7,8]. To select the optimal content of UPTFE in the composite, its effect on the physic-mechanical characteristics of PTFE was studied.…”

“…As a result, they show low adhesive strength, which reduces mechanical characteristics of PCM made based on them. Therefore, among carbon fillers, modified carbon fibers with low surface energy close to that of PTFE are of interest [7]. It is known that introduction of modified milled carbon fibers makes it possible to maintain the strain-strength characteristics of PCM at the level of those of the original polymer.…”

Tribological properties of ptfe filled with carbon fibers and solid lubricant

“…As can be seen from Figure 1, the introduction of CF/WS2 and CF/UPTFE in PTFE leads to the preservation of the deformation-strength properties of polymer composites at the level of the initial polymer matrix. This is because used plasma-chemically modified carbon fibers (BELUM) that have low surface energy and therefore are compatible with PTFE [11].…”