Tribological characterization of nanoparticle filled PTFE: Wear-induced crystallinity increase and filler accumulation

• Published in: Express polymer letters 2021-10, Vol.15 (10), p.972-986
• Main Authors: Toth, L. F., Szebenyi, G., Sukumaran, J., De Baets, P.
• Format: Article
• Language: English
• Subjects: Accumulation; Alumina; Aluminum oxide; Boehmite; Chain scission; Chemical reactions; Contact pressure; Crystal structure; Crystallinity; filler accumulation; Fillers; Friction; Graphene; Molecular chains; nanoparticle-filled ptfe; Nanoparticles; Particle size; polymer composites; Polymers; Polytetrafluoroethylene; Room temperature; Sintering; sliding wear; Steel; Tribology; Wear mechanisms; Wear resistance; wear-induced crystallinity
• ISSN: 1788-618X; 1788-618X
• DOI: 10.3144/expresspolymlett.2021.78

The present research aims to clarify the friction and wear behavior, the transfer layer formation, and the wear mechanism of mono-filled polytetrafluoroethylene (PTFE). A well-known limitation of PTFE is the low wear resistance, which can be surpassed with the use of micro- or nanoparticles. The applied fillers were graphene, alumina (Al2O3), boehmite alumina (BA80), and hydrotalcite (MG70). The samples were produced by room temperature pressing - free sintering method. All specimens were tested with a pin-on-disc tribo-tester in dry contact condition against 42CrMo4 steel disc counterface with 3 MPa contact pressure and 0.1 mm/s sliding speed. PTFE filled with 4 wt% Al2O3 achieved the highest wear resistance; the increase was more than two orders of magnitude compared to the neat PTFE. This improvement comes from the protective transfer layer formation due to the Al2O3 and the iron-oxide accumulation on the polymer contact surface. Significant wear-induced crystallinity was also registered, which originated from the mechanical chain scission of the PTFE molecular chains during the wear process.