Abstract
Paper-based friction materials are porous materials that exhibit anisotropy; they exhibit random pore sizes and quantities during their preparation, thereby rendering the control of their pore structure difficult. Composites with different pore structures are obtained by introducing chemical foaming technology during their preparation to regulate their pore structure and investigate the effect of pore structure on the properties of paper-based friction materials. The results indicate that the skeleton density, total pore area, average pore diameter, and porosity of the materials increase after chemical foaming treatment, showing a more open pore structure. The addition of an organic chemical foaming agent improves the curing degree of the matrix significantly. Consequently, the thermal stability of the materials improves significantly, and the hardness and elastic modulus of the matrix increase by 73.7% and 49.4%, respectively. The dynamic friction coefficient increases and the wear rate is reduced considerably after optimizing the pore structure. The wear rate, in particular, decreases by 47.7% from 2.83 × 10−8 to 1.48 × 10−8 cm3/J as the foaming agent content increases. Most importantly, this study provides an effective method to regulate the pore structure of wet friction materials, which is conducive to achieving the desired tribological properties.
Highlights
Paper-based friction materials are typically synthesized via wet paper-making methods, using reinforced fibers and friction modifiers as the main raw materials to create preforms, which are impregnated with binders and cured via hot pressing [1,2,3,4]
DPT decomposed into nitrogen, formaldehyde, and hexamethylene tetramine (HMTA) after heating [24]
The mass loss in the second stage was primarily caused by the decomposition of HMTA and biuret generated in the first stage, which resulted in solid residues
Summary
Paper-based friction materials are typically synthesized via wet paper-making methods, using reinforced fibers and friction modifiers as the main raw materials to create preforms, which are impregnated with binders and cured via hot pressing [1,2,3,4]. The pore structure control of the material is performed based on a single method, i.e., primarily by changing the material thickness or hot-pressing curing parameters. An effective method is necessitated to regulate the pore structure of paperbased friction materials such that the materials can yield a higher μd while maintaining a low wear rate. Paper-based friction materials with different pore structures can be obtained by changing the amount of foaming agent. Few studies have applied chemical foaming technology to regulate the pore structure and investigate its effect on the overall properties of paper-based friction materials. Paper-based friction materials with different pore structures were achieved by introducing chemical foaming technology during their preparation. The strengthening effect of the chemical foaming system on the matrix, and the impact mechanism of the pore structure on the tribological performance were investigated
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