Preparation of Novolac composites with improved properties for disk brake systems

摘要

The effect of composition and the dry and wet operating conditions on the adhesive wear resistance of polymeric composite materials were studied in this work. The composite are designed to be used as pads for disc brake system of heavy vehicles. The composites were prepared with weight ratios, Ψ, in the range: 60-90% using the dry method. The composites were reinforced with a number of fillers and friction improvement agents like: silicon carbide, carbon fibers, alumina, etc at various ratios to establish diverse properties in comparison with Novolac resin. The used ceramic disc brake materials were also utilized in this preparation at certain weight ratios as one of the components of the composites. The wear resistance measurements indicated that a ratio higher than 70% will reduce the hardness of the disc material. Thus, composites with 60% Novolac weight ratio, which indicated the best performance, were prepared with 14-22% of the hardener, the HMTA. The study revealed that the abrasion rate decrease with the reinforcement of the Novolac, i.e., increase in abrasion resistance, especially when the carbon fibers ratio were increased from 1.5 to 3.0%. Meanwhile, the increase of the hardener resulted in increase in the in wear resistance. Further, it appears that the rate of abrasion changes from moderate to in accordance with operating conditions like the applied load, operating time and sliding distance. To mimic the real application conditions, the specimens were subjected to rain water by spraying for 2 min during operation. The wetting caused a lowering of the wear resistance. However, in comparison with the available disc brake materials, our specimens proved either comparable or better performance.