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The paper addresses utilization of 0-14.6 vol.% alkaline-treated walnut shell powders (WSPs) as a functional filler in the proposed eco-friendly brake friction materials. Five non-asbestos friction material samples containing WSP and jute fibers from biomass as biodegradable components were prepared, also including several from natural resources, such as wollastonite, basalt fibers, zircon, barite, and vermiculite. The friction-wear properties of the prepared composites were tested by using Chase friction performance testing device. Furthermore, an extension evaluation method was introduced to rank the composites based on their overall friction-wear characteristics. The coefficient of friction (COF) and wear rate of the samples could be effectively improved, especially for the sample with a WSP content 45.6 vol.%. With confirmation of the analysis and characterization results, chars were very possibly formed by the degradation of organic ingredients, such as WSP and jute fibers, which played a key role in affecting the friction performance of the friction composites.

Eco-friendly brake friction composites with good friction performance were developed. The raw materials utilized were selected according to eco-friendly criterion that natural products should be preferably chosen. The formulations are composed of plant flax fiber, mineral basalt fiber, and wollastonite as reinforcements, natural graphite as solid lubricant, zircon as abrasive, vermiculite and baryte as functional and space fillers, and cardanol-based benzoxazine-toughened phenolic resin as binder. To isolate the flax fibers, chemical and physical methods including drying, room temperature alkaline solution, and acid steam treatment were performed and fibers with micro-fibrillated structure on the surface were formed. A new cardanol-based benzoxazine synthesized by the reactions among cardanol, aniline, and formaldehyde was used as toughening for phenolic resin. The effects of both the content of treated flax fibers and friction temperature on friction performance, friction coefficient and specific wear rate, of the friction composites were evaluated by the extension evaluation method.

Novel segmented carborane-containing polyurethane (PUR 2-5) is synthesized from hydroxyl-terminated carborane-containing prepolymer (P3) as soft segment and isocyanate-terminated carborane-containing prepolymer (P5) as hard segment by different ratio of P3 and P5. The prepared carborane-containing polyarylesters and polyurethanes (PURs) are characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). Their mechanical properties and thermal stability are measured, while the dosage of carborane biphenol is 5-10 wt %, the tensile strength is up to 20 MPa, and thermal gravimetric analyzer (TGA) curves indicate that the carborane group effectively reduces the degradation rate of carborane-containing polyurethane, which is fairly stable above 300 C and with char yield exceeding 40%.