Evidence of chemical compatibilization reaction between poly(ether ether ketone) and irradiation-modified poly(tetrafluoroethylene)

Abstract

Poly(tetrafluoroethylene) (PTFE) micropowder is used as a lubricant in thermoplastic high-performance polymers, for example, in poly(ether ether ketone) (PEEK) to improve their tribological properties regarding friction and wear significantly. The achievable effect for improving such properties by using PTFE is not only determined by the added amount of PTFE micropowder in the PEEK-PTFE compound but rather by the possibility to couple and compatibilize the PTFE with the matrix material chemically that has a direct influence on the distribution of the PTFE particles in the polymer matrix and causes improved tribological and mechanical properties. The proof of a chemical reaction between PTFE and PEEK is difficult because the high-molecular weight PEEK is insoluble in all common solvents. The evidence of chemical coupling reaction between PEEK and irradiation-modified PTFE is shown by model studies using reactive OH-terminated PEEK oligomers. The use of diphenyl sulfone as a high-boiling reaction medium was necessary for the precondition to melt both reactants. In this way, qualitative differences have been achieved and confirmed using Fourier transform infrared spectroscopy. Thus, a safer and indirect detection of the chemical coupling (cc) between PEEK and PTFE (PEEK–PTFE–cc) was achieved.