Polymeric composites represent an advantageous choice for brake pads materials, offering a good balance between costs and performances. In this work, composite brake pads based on barite, potassium titanate and aramid fibers embedded in a polymeric matrix of phenol formaldehyde resin have been wear-tested in laboratory against a class FC-250 cast iron using a car brake simulator and then characterize using different microscopic and spectroscopic techniques. Four main wear mechanisms were observed depending on brake pad composition, as follows: tribolayer formation, ceramic crystal pull-out, cleavage of the C–N bond in aramid pulp fibres, and dissolution of barite to produce either ammonium or potassium sulphate. In the presence of potassium titanate, both wear rate and tribolayer area coverage were clearly reduced. Spectroscopic techniques enabled us to resolve the physicochemical degradation mechanisms behind brake performance, suggesting their potential use as in situ probes.

Polyetheretherketone (PEEK) is a popular polymeric biomaterial which is primarily used as an intervertebral spacer in spinal fusion surgery; but it is developed for trauma, prosthodontics, maxillofacial, and cranial implants. It has the purported advantages of an elastic modulus which is similar to native bone and it can be easily formed into custom 3D shapes. Nevertheless, PEEK's disadvantages include its poor antibacterial resistance, lack of bioactivity, and radiographic transparency. This study presents a simple approach to correcting these three shortcomings while preserving the base polymer's biocompatibility, chemical stability, and elastic modulus. The proposed strategy consists of preparing a PEEK composite by dispersing a minor fraction (i.e., 15 vol%) of a silicon nitride (Si3 N4 ) powder within its matrix. In vitro tests of PEEK composites with three Si3 N4 variants-β-Si3 N4 , α-Si3 N4 , and β-SiYAlON-demonstrate significant improvements in the polymer's osteoconductive versus SaOS-2 cells and bacteriostatic properties versus gram-positive Staphylococcus epidermidis bacteria. These properties are clearly a consequence of adding the bioceramic dispersoids, according to chemistry similar to that previously demonstrated for bulk Si3 N4 ceramics in terms of osteogenic behavior (vs both osteosarcoma and mesenchymal progenitor cells) and antibacterial properties (vs both gram-positive and gram-negative bacteria).

There are various requirements, such as NVH performance, wear resistance, stability in friction level, rotor compatibility, etc. for friction materials of brake pads. In these materials, potassium titanate fiber is widely used due to its specific benefits that contribute to stability in friction level and low wear. Focusing on titanate compounds including potassium titanate fiber, we have proceeded with an analysis of the relationship between their powder properties and brake performance. Before the evaluation, various types of titanate compounds were prepared for comparison, according to their chemical composition, size and crystal structure. We measured the powder properties by a powder tester. The brake performance tests have been conducted with NAO formulations in accordance with JASO C-406 P1 category. The test results showed some specific benefits for brake performance in the formulation with TERRACESS added.