Paper-based Friction Materials Research Articles

Polydopamine coating grown on the surface of fluorinated polymer to enhance the self-lubricating properties of lignin-cellulose based composites

In this paper, a novel ethanol-water Tris buffer system was developed to construct a polydopamine (PDA) protective layer on the surface of polytetrafluoro-wax (PFW) to obtain PFW@PDA with excellent hydrophilicity. The wood-based slurry was obtained by solvent encapsulation and lignin-cellulose assisted ball milling process using waste poplar powder and flake graphite as raw materials. PFW@PDA exhibited excellent dispersion stability in such aqueous slurry and the water was removed from the slurry by vacuum filtration to obtain paper-based composite films. Based on the self-reinforcement of the lignin-cellulose cross-linked network, construction of graphene thermal conductivity network, and the effectiveness of PFW@PDA for wear reduction and self-lubricating. This composite film exhibits excellent water resistance, good thermal stability, and superior mechanical properties. The friction coefficient and wear rate were reduced by 71.3 % and 166.7 %, respectively, compared with the unmodified material. Besides, the end-of-life products can be recycled by mechanical crushing in water, which exhibits a good balance between wear resistance and sustainability, providing a new idea for improving the hydrophilicity of fluorinated polymers and enhancing paper-based friction materials.

Effects of Pre-Curing on the Structure and Properties of Paper-Based Materials.

Paper-based friction material is a typical paper-based composite that is usually cured via hot-pressing. This curing method does not account for the effect of pressure on the matrix resin, resulting in uneven distribution of resin in the material and reducing the mechanical properties of friction materials. To overcome the above shortcomings, a pre-curing method was introduced before hot-pressing, and the effects of different pre-curing degrees on the surface morphology and mechanical properties of paper-based friction materials were studied. The pre-curing degree significantly affected the resin distribution and interfacial bonding strength of the paper-based friction material. When the material was cured at 160 °C for 10 min, the pre-curing degree reached 60%. At this point, most of the resin was in a gel state, which could retain abundant pore structures on the material surface without causing mechanical damage to the fiber and resin matrix during hot-pressing. Ultimately, the paper-based friction material exhibited improved static mechanical properties, decreased permanent deformation, and reasonable dynamic mechanical properties.

Sustainable, recyclable, and highly wear-resistant wood matrix as a new paper-based friction material

Sustainable, recyclable, and highly wear-resistant wood matrix as a new paper-based friction material

Friction-Wear Characteristics of Carbon Fiber Reinforced Paper-Based Friction Materials under Different Working Conditions

To study the friction and wear performance of carbon fiber reinforced friction materials under different working conditions, paper-based friction materials with different fibers were prepared. Experiments on the SAE#2 test bench were conducted to study the infectors including friction torques, surface temperature, coefficient of friction (COF), and surface morphologies. The results were analyzed, which indicated that the carbon fiber reinforced friction material could provide a higher friction torque and a lower temperature rising rate under the applied high pressure and high rotating speed conditions. As the pressure increased from 1 MPa to 2.5 MPa, the friction torque of plant fiber reinforced material increased by 150%, the friction torque of carbon fiber reinforced material increased by 400%, and the maximum temperature of plant fiber reinforced and carbon fiber reinforced material reached the highest value at 1.5 MPa. Thus, carbon fibers not only improved the COF and friction torque performance but also had advantages in avoiding thermal failure. Meanwhile, carbon fiber reinforced friction materials can provide a more stable COF as its variable coefficient (α) only rose from 38.18 to 264.62, from 1 MPa to 2.5 MPa, which was much lower than the natural fiber reinforced friction materials. Simultaneously, due to the good dispersion and excellent mechanical properties of PAN chopped carbon fibers, fewer pores formed on the initial surface, which improved the high wear resistance, especially in the intermedia disc.

Recent Findings in Fatigue of Paper-Based Friction Materials for Clutch

Recent Findings in Fatigue of Paper-Based Friction Materials for Clutch

Optimization of pore structure and wet tribological properties of paper-based friction materials using chemical foaming technology

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.

Effects of the Addition of Rare Earth on Properties of Paper-Based Friction Materials

To investigate the effects of the addition of rare earth (RE) on properties of paper-based friction materials, six samples with LaCl3•7H2O contents of 0, 1, 2, 3, 4, and 5wt% were prepared. The results showed that adding a certain amount of RE can greatly improve the interfacial bonding strength, but when the content of RE exceeds 3wt%, it has a negative effect on the bonding strength. In addition, with the increase of RE contents, the thermal diffusivities and thermal conductivities of the materials reached maximum values at 3wt%. When the RE content is 4wt%, the sample has the best wear resistance and the friction coefficient also reaches 0.1449. This work indicated that the addition of the RE can immensely enhance the performance of paper-based friction materials, and lays a foundation for the improvement of interfacial bonding strength of paper-based friction materials in the future.

Coefficient of friction and wear rate of paper-based composite friction material against 65Mn steel

Studies have shown that reinforced paper-based friction material with 600 µm carbon fiber length possesses a high dynamic friction coefficient but is subjected to abrasive wear during sliding contact. This work is devoted to further investigate the effect of operating variables on this friction material subjected to high operating conditions. A pin-on-disc test was carried out to determine the tribological behavior of this friction material sliding against 65Mn steel. The friction and wear rate results from measurements were discussed. The highest friction value of about 0.3 was obtained by varying the applied load at 120 N while the lowest friction value close to 0.02 was obtained when the sliding speed was 0.026 m/s. Increasing the sliding speed above 0.30 m/s caused constant temperature (175 °C) to fluctuate due to high friction heat generation on the sliding surface. The highest wear rate was 1.42 × 10−15m3/Nm by varying the sliding speed at 1.31 m/s. In contrast, the lowest wear rate was 2.1 × 10−16m3/Nm when the temperature was at 400 °C.

Effect of pore structure on mechanical and tribological properties of paper-based friction materials

To explore the effect of the pore structure of paper-based friction materials on the friction and wear properties, the composites with different pore structures were obtained using physical foaming technology. Results displayed that the bulk density and average pore size of composites increased after the foaming treatment, while the total pore area and porosity showed a tendency to gradually decrease after hot pressing. The tensile and interlaminar shear strength of the composites were improved by 18% and 42% respectively after the optimization of the pore structure. Moreover, the application of foaming technology significantly increased dynamic friction coefficient and reduced wear rate of the friction materials. In particular, the wear rate of paper-based friction materials decreased by 44.6% from 1.57x10−8 cm3/J to 0.87x10−8 cm3/J with the increase of foaming agent content. Most importantly, the pore structure of paper-based friction materials can be effectively changed due to the introduction of physical foaming technology. This research lays a solid foundation for optimizing the pore structure of paper-based friction materials in the future.

A new kind of resin-based wet friction material: Non-woven fabrics with isotropic fiber networks as preforms

As an alternative to short fibers, non-woven fabrics (NWFs) were made using different types of long fibers to optimize the performance of paper-based friction materials and their technology. In this investigation, the fillers and resin were impregnated into these NWFs to prepare three kinds of wet friction material. The tribological, mechanical, and thermal properties of the new wet friction material were studied. The results indicate that the dynamic friction coefficient of the new friction material is approximately 0.12 and the static friction coefficient is approximately 0.15; the better wear rate is 0.81334 × 10-14 m3·(N·m)-1. In addition, the temperature for 10% mass loss yielded 100 °C enhancement and the tensile strength was improved by 200%, compared to previously reported values. Most importantly, the advantages include a simple preparation flow, low cost, and resource conservation. This is a promising approach for the future development of paper-based friction materials.

Friction and wear properties of three different steels against paper-based friction material

Purpose The purpose of this paper is to study friction and wear properties of three types of steels against paper-based friction disc, including 65Mn, 20#steel and 30CrAl, so as to obtain the appropriate working conditions for different friction materials in the transmission system. Design/methodology/approach Based on actual working conditions, pin-on-disc tests are conducted on a universal material tester. The two evaluation indexes, including average friction coefficient and variation coefficient, are introduced to analyze the different friction properties among three types of steel. Furthermore, the temperature-dependent wear pattern and wear depth are subsequently studied. Findings The results show that 65Mn is more suitable for working under heavy load and low velocity, but 30CrAl and 20#steel are suitable for working under light load and high velocity. Moreover, wear primarily occurs on paper-based material and peaks at about 325. Practical implications This research of different materials and friction property for friction pairs is helpful to improve the performance and prolong the service life of transmission systems. Originality/value Suitable working conditions of different friction materials are obtained, and the correlation between wear and decomposition in high temperature is verified.

Comparison of the Friction and Wear Characteristics between Copper and Paper Based Friction Materials.

Copper-based friction material (CFM) and paper-based friction material (PFM) are the two most commonly used clutch friction materials. The friction and wear characteristics of these two kinds of friction materials under dry conditions were investigated by the pin-on-disc test over a broad range of applied loads, rotating speeds and ambient temperatures. Before experiments, the running-in test was conducted to stabilize the coefficient of friction (COF) and wear amount of the test samples. After experiments, the metallographic micrographs of the tested samples were presented to investigate the wear mechanisms. Experimental results showed that both the COF and wear depth of the CFM are much greater than these of PFM. The COF of CFM decreases with the increase of applied load, and changes slightly with the variation of rotating speed, whereas it increases first and then decreases with the increase of ambient temperature. However, the COF of PFM decreases dramatically with the increase of the rotating speed and ambient temperature, while it remains stable at first and then decreases slowly as the applied load increases. Additionally, under such three working conditions, the wear depth of CFM changes linearly, while the wear depth of PFM varies greatly. This study can be used as a guide for selecting friction materials for clutches with different applications.

Effect of LNBR Content on the Properties of the Carbon Fiber–Reinforced Paper-Based Friction Materials

The binder plays an important role in transmitting loads and maintaining the stability of paper-based friction materials. Four kinds of binder-based carbon fiber–reinforced paper-based friction materials were prepared. The effects of the ratio of the liquid nitrile butadiene rubber (LNBR) and phenolic resin (PF) content on the friction and wear properties were investigated. It was found that the dynamic and static friction coefficients would increase with an increase in LNBR content. When the content of PF and LNBR was kept at 20 wt%, the friction materials had lower wear rates and better thermal stability. These phenomena indicated that a certain amount of rubber in the binder could improve the friction and wear properties of the friction materials.

Effect of pre-impregnated organosilicon layer on friction and wear properties of paper-based friction materials

Paper-based friction materials contain a variety of inorganic and organic materials, and organosilicon can be well linked with organic and inorganic compounds due to its inorganic and organic functional groups. Therefore, in this work, paper-based friction materials with different organosilicon contents were obtained by the pre-dipping the preform. The results displayed that adding a small amount of organosilicon to the paper-based friction materials could increase the coefficient of static friction, but also reduced the coefficient of dynamic friction and wear rate of the paper-based friction materials. When the content of organosilicon in the materials was more than 5 wt%, the wear rate of the materials tended to be stable. And the paper-based friction materials with 7.5 wt% organosilicon content had the highest coefficient of static friction. By testing the variation of the coefficient of friction, it was found that the materials with 7.5 wt% organosilicon content had the best stability.

Synergetic effect of epoxy resin and carboxylated nitrile rubber on tribological and mechanical properties of soft paper-based friction materials

Abstract In order to improve tribological and mechanical properties of rubber-based wet friction materials, five kinds of paper-based friction materials were prepared using the mixture of different ratios of epoxy resin (EP) and carboxylated nitrile butadiene rubber (XNBR) as a dual matrix. When the proportion of XNBR exceeds 40% in binder, the wear rate of paper-based friction materials begins to reduce, while the tensile strength, toughness and dynamic friction coefficient remain unchanged. In the end, the wear rate of the material for 80% XNBR in binder is reduced by 29% compared with material for 40%. This is attributed to ionic crosslinking network involved with divalent substances in fillers combining with the vulcanization effect of EP on XNBR.

Assessment of Wear Characteristics of Paper-Based Wet Friction Materials

A wet clutch synchronizes the speed and transmits power from an engine or motor to a drive train by mechanical coupling between a friction disk and a separate disk. The performance of a wet clutch may be significantly dependent on the friction and wear characteristics of paper-based friction materials. In this work, the wear characteristics of paper-based friction materials were experimentally investigated using a pin on reciprocating plate tribo-tester. In particular, the wear characteristics of paper-based friction materials with and without carbon fibers were assessed in a boundary lubrication state with respect to normal force and sliding speed. The tests found that the wear rate of paper-based friction materials increased with increasing normal force and sliding speed. The wear rates were found to vary in the range of 10-6-10-4 mm3/(N·cycle). In addition, paper-based friction material with carbon fiber exhibited relatively larger friction and wear characteristics than those without carbon fibers. It was observed that the carbon fibers were broken due to the sliding contact, which may have contributed to the wear progression. The outcomes of this work may be helpful in gaining a better understanding of the tribological characteristics of paper-based friction materials in order to enhance the lifetimes of wet clutches.

Dynamic Behavior of Real Contact of Paper-Based Wet Friction Material

Dynamic Behavior of Real Contact of Paper-Based Wet Friction Material

ZnO nanowires decoration on carbon fiber via hydrothermal synthesis for paper-based friction materials with improved friction and wear properties

Two-step growth of ZnO nanowires (NWs) on carbon fiber (CF) surface via hydrothermal synthesis was studied and their application in the preparation of paper-based friction materials by wet-forming process was also investigated. SEM and EDS results showed a dense and uniform ZnO NWs layer with vertical alignment was well established on surface of CFs. UV–vis spectra and XRD characterization further confirmed the formation of ZnO NWs on CFs surface. In comparison with control sample (paper-based friction material containing pristine CFs), the modified sample (paper-based friction material containing modified CFs) exhibited higher and more stable dynamic friction coefficient and greater wear resistance. It was concluded that the CFs@ZnO NWs had excellent tribological properties and was highly promising for wet paper-based friction material.

Friction and wear behavior of SiC particles deposited onto paper-based friction material via electrophoretic deposition

Abstract In order to improve the friction and wear properties of the paper-based friction materials, SiC particles (SiCp) were uniformly deposited onto the paper-based friction material via electrophoretic deposition with 300 V, 400 V and 500 V deposition voltages, obtaining the SiCp-content of 10.8, 15.9 and 22.9 wt%. The microstructure and thermal stability of the paper-based friction materials were characterized by scanning electron microscope (SEM) and thermogravimetry (TG). And the porosity, mechanical and tribological properties of samples were tested by mercury injection apparatus, electromechanical universal testing machine and friction tester. The results show that the uniform distribution of SiCp in the paper-based friction materials decreases the porosity and obviously improves the thermal stability and mechanical properties. Meanwhile, the incorporation of SiCp increases the stability of friction coefficient and the wear resistance of paper-based friction materials. Especially, the wear rate of paper-based friction material with 400 V deposition voltage treatment (CP400) for optimal SiCp-content of 15.9% decreases by 51.2% from 5.8 × 10−14 to 2.8 × 10−14 m3/(N·m) compared with that of the bare paper-based friction material (CP0). The electrophoretic deposition techniques provide the possibility of uniform addition of micro-nano particles to the paper-based friction material, which is beneficial to improve the friction and wear properties.

Influence of Modified Carbon Fiber on Properties of Paper Based Friction Materials

The paper adopts modified carbon fiber with Meldrum's acid and silane coupling agent (KH-550), then add the modified carbon fiber to the paper based friction materials. The paper aims to explore the changes of modified carbon fiber in its surface structure and properties by electron microscopy and infrared spectral analysis, and the effect of anionic microparticle forming retention aid system comprised of lithium soapstone-cationic polyacrylamide (CPAM) on mechanical properties and retention of paper based friction materials. Compared with the addition of unmodified carbon fiber to paper based friction materials, the addition of modified carbon fiber with Meldrum's acid, silane coupling agent, Meldrum's acid and silane coupling agent enhance the tensile strength of paper based friction materials. The tensile index of paper based friction materials was separately enhanced by 64.87 %, 91.38 % and 28.88 %. Compared with the paper based friction materials without the anionic microparticle forming retention aid system, the basis weight of paper based friction materials increased by 13.97 %.