Mechanical and wear behaviour of PEEK, PTFE and PU: review and experimental study

Soft polymers such as polyether ether ketone (PEEK), polyurethane (PU) and polytetrafluoroethylene (PTFE) have gained significant research interest in the last few decades owing to their excellent material properties which can be harnessed to meet the demands of various applications such as biomedical implants and accessories, insulation panels to cooking utensils, inner coating material for non-stick cookware etc. In the present study, we provide a comprehensive review on the mechanical and tribological behaviour of PEEK, PU and PTFE polymers. Samples of these materials were also fabricated and the experimentally obtained tensile strength, flexural strength, wear rate and coefficient of frictions were ascertained with values reported in literature. It is highlighted that coefficient of friction of polymers were highly dependent on the surface texture of the polymer’s surface; where an uneven surface exhibited higher coefficient of friction. Perspectives for future progress are also highlighted in this paper.

Jet milling industrialization of sticky active pharmaceutical ingredient using quality-by-design approach

Jet milling is frequently used in pharmaceutical industry to achieve different objectives. It can be used as enabling technology to overcome poor water solubility linked to hydrophobic active of pharmaceutical ingredient (API) by reducing the particle size and therefore increasing the dissolution rate. Alternatively, jet milling can be used either to enhance blending efficiency of API with excipient in case of formulation at low dosage strength or to achieve the required particle size for inhalation therapy. In this study, development of commercial manufacturing process of sticky API and its industrialization are described. The methodology used is based on quality-by-design approach to deliver safe, effective and robust manufacturing process. The study showed that the specific energy is a key factor that drives particle size during jet milling and the scale-up from lab to industrial scale. After understanding the process, a design space was built where different zones such as operating point, operating space (where the product is compliant to specification despite variability of process parameters), and the knowledge space were outlined. Finally, an industrial installation was proposed to deliver product with high productivity yield, compliant with safety regulation, and cleanable in place.

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

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.