Brake Pad Formulation Research Articles

Exploring the tribological impact of micaceous additives in copper‐free automobile brake friction composites

AbstractThis study investigates the tribological impact of incorporating micaceous additives in copper‐free brake friction composites for automotive applications. Four brake pad formulations were created, each containing different amounts of muscovite and phlogopite, ranging from 0% to 10% by weight. A brake pad comparison was conducted by replacing mica with synthetic barites. The physical, thermal, mechanical, and chemical properties of the fabricated brake friction composite were examined. Tribological features were evaluated through inertia brake dynamometer testing following the JASO‐C‐406 schedule. Scanning electron microscope (SEM) analysis delved into contact plateau formations and back transfer patches on the brake pad's surfaces. Notably, phlogopite‐based pads exhibited enhanced thermal stability and efficient heat dissipation, contributing to sustained tribological performance. Overall, the comprehensive evaluation using the multiple objective optimization by ratio analysis (MOORA) method positioned phlogopite‐based brake pads as the optimal choice for optimized braking performances.Highlights Exploration of micaceous additives as an ingredient in brake friction composite. Phlogopite‐based brake pads showed better fade and recovery performance. Phlogopite‐based brake pads exhibited low pad wear and rotor wear. MOORA optimization positioned phlogopite‐based brake pads as the optimal choice.

Unveiling optimisation of the manufacturing parameters of brake pad formulation developed from silver nanoparticle modified carbon nanotubes from rice husks

Unveiling optimisation of the manufacturing parameters of brake pad formulation developed from silver nanoparticle modified carbon nanotubes from rice husks

Effect of potassium titanate fibres and metal sulphides in the tribological behaviour of brake friction composites

In a brake system, brake friction composites are essential for converting kinetic energy into frictional heat. An optimal brake friction composite should ensure a stable coefficient of friction under extreme operational conditions. This study examines the tribological performance of brake friction composites incorporating potassium titanate fibres and metal sulphide lubricants in standard brake pad formulation. Brake friction composites were engineered by varying the potassium titanate fibre content from 10 to 30 %, while the lubricant mixture (comprising graphite, MoS2, Bi2S3 and Sb2O3) was proportionally adjusted from 27 to 7 %, with the filler and binder concentrations held constant throughout the formulation. The phenolic resin-based composites were characterised for their physical, chemical and mechanical properties in accordance with the IS 2742 (Part 4) standard. The tribological performance of the fabricated composites was evaluated using a rotating drum setup, following the SAE J661 procedure. The worn surfaces of the samples were analysed to identify wear mechanisms utilising scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). The results demonstrated that the optimal combination of potassium titanate fibres and metal sulphide lubricants significantly influences wear resistance and friction stability, with varying degrees of primary and secondary plateau formation observed. This comprehensive characterisation provides valuable insights into the material's behaviour under operational conditions, guiding the development of advanced brake friction composites.

Alteration of Hordeum vulgare and Sinapis alba germination and early growth in response to airborne low-metallic automotive brake wear debris

Road transportation significantly contributes to environmental pollution, both in terms of exhaust and non-exhaust (brake wear) emissions. As was proven, brake wear debris is released in a wide variety of sizes, shapes, and compositions. Although studies confirming the possible adverse health and environmental impact of brake wear debris were published, there is no standardized methodology for their toxicity testing, and most studies focus only on one type of brake pad and/or one test. The lack of methodology is also related to the very small amount of material released during the laboratory testing. For these reasons, this study deals with the mixture of airborne brake wear debris from several commonly used low-metallic brake pads collected following the dynamometer testing. The mixture was chosen for better simulation of the actual state in the environment and to collect a sufficient amount of particles for thorough characterization (SEM, XRPD, XRF, chromatography, and particle size distribution) and phytotoxicity testing. The particle size distribution measurement revealed a wide range of particle sizes from nanometers to hundreds of nanometers, elemental and phase analysis determined the standard elements and compounds used in the brake pad formulation. The Hordeum vulgare and Sinapis alba were chosen as representatives of monocotyledonous and dicotyledonous plants. The germination was not significantly affected by the suspension of brake wear debris; however, the root elongation was negatively influenced in both cases. Sinapis alba (IC50 = 23.13 g L−1) was more affected than Hordeum vulgare (IC50 was not found in the studied concentration range) the growth of which was even slightly stimulated in the lowest concentrations of brake wear debris. The plant biomass was also negatively affected in the case of Sinapis alba, where the IC50 values of wet and dry roots were determined to be 44.83 g L−1 and 86.86 g L−1, respectively.

Design of a friction material for brake pads based on rice husk and its derivatives

Commercial vehicle brake pads play an important role in the environmental impact caused by road transport. Their complex raw material requirements and increasingly prevalent contribution to traffic pollution is forcing the industry to look for alternative solutions. Natural lignocellulosic fibers have already been investigated as sustainable brake pad ingredients, and while braking performance results appear promising, important characteristics such as wear and particulate matter emission are either deteriorated or outright neglected. In this study, rice husk, a byproduct of the agricultural industry, is investigated as possible environmentally friendly natural ingredient. Friction material samples based on a commercial formulation were modified by adding different percentages of both rice husk and rice husk ash, the product of a thermal treatment of the former, and then tested with a modified pin-on-disc tribometer. The experimental setup included collecting instruments for emitted wear particles. 6 to 12 wt% of rice husk showed preservation of the braking performance whilst possibly improving wear and emission characteristics of the friction material. Higher amounts of modifications led to deterioration of tribological properties. Overall, this investigation suggest that limited yet substantial amounts of rice husk could successfully substitute conventional filler ingredients in brake pad formulations, as an effective approach in lowering their environmental impact.

Biodegradable cow dung for brake friction material: a preliminary investigation

The purpose of the study is to develop a biodegradable and non-asbestos/copper-free brake pad formulation. The possibility of using organic cow dung particles as an eco-friendly reinforcement in friction material for brake pads is investigated. Sodium hydroxide (NaOH) treated cow dung is Sun dried and ground to an average particle size of 200 microns. It is reinforced in epoxy resin in weight fractions of 5%, 10%, 15%, 20% and 25% along with other fillers and friction stabilizers. The composite samples are subjected to density, thermal conductivity, microhardness and tensile strength evaluation for mechanical characterization. Pin on disc testing is done to identify the coefficient of friction (CoF), wear coefficient and specific wear rate as a part of tribological characterization. The scanning electron micrographs and EDAX analysis of worn out surface is performed to study the wear mechanism. Promising results are seen with composite samples reinforced with 15% cow dung particles in terms of better microhardness, tensile strength, stable coefficient of friction and low wear. The investigation could guide industries working on brake pad materials. This could open up an era of low cost, organic and eco-friendly alternative to carcinogenic asbestos/copper in friction materials.

Rice husk as a natural ingredient for brake friction material: A pin-on-disc investigation

The addition of the rice husk in a new eco-friendly Cu-free brake pad formulation was investigated in this study. Rice husk (RH) is a natural agro-waste residue with relatively high silica content, which should display abrasive properties that are not easily found in other natural materials. In this study, tribological properties of three friction materials were investigated using a pin-on-disc (PoD) tribometer. The three formulations were prepared adding to a common composition, each one of the following components: 6 wt% of grinded rice husk (material code: F-RH); this same amount of rice husk, after heat treatment at 600 °C (material code: F-RHT); and finally 6 wt% of alumina (F-AL) in place of rice husk, respectively. This latter material was meant to characterize the specific role of the natural ingredient. During PoD tests the evolution of the friction coefficient was followed, along with the concentration of the emitted airborne particles. The F-RHT showed very promising properties, depending on the particular characteristics of the friction layer forming onto the pin surface. This layer turned out to be compact and it was highly covering the surface of the F-RHT material, thanks to the positive effect of the silica particles from RH. The F-RH featured good behavior in terms of low wear and low emissions. In both cases, the rice husk showed up as a potential valuable alternative as a natural brake pad ingredient.

Organic profiles of brake wear particles

Four brake pads were tested in a bench dynamometer under test cycles with different braking severities: i) two types of conventional brake pads (low steel 1 and 2), and ii) two types of non-asbestos organic brake pads (NAO 1 and 2) with non-ferrous materials. Wear particles (PM10) were analysed for total carbon by a thermo-optical method and then solvent-extracted and analysed by gas chromatography–mass spectrometry. In general, the test protocols with less braking and lower temperatures gave rise to much lower PM10 levels. Total carbon accounted for PM10 mass fractions in a wide range (5.07–75.4%), generally decreasing with the severity of the braking cycles. More than 150 organic compounds were quantified, comprising aliphatics, polycyclic aromatic hydrocarbons (PAHs), alcohols, several types of acids (alkanoic, alkenoic, diacids and others), glycol/glycerol derivatives, plasticisers, sugars, sterols and various phenolic constituents. Globally, larger amounts of most of these compounds were emitted by NAO 2 under the smoothest braking cycle. Several correlations between compounds with the same functional groups were established. No PAH with five or more benzenic rings was detected. The differences in composition and concentrations are discussed based not only on the characteristics of the braking circuits, but also on the diverse quantities and types of organic compounds used in the brake pad formulations.

Experimental Study on the Performance Characteristics of Non-asbestos Brake Pads Using a Novel Friction Testing Machine

The friction, wear and mechanical properties of a new non-asbestos brake pad formulation called Premix were investigated. A novel friction-testing machine was utilized to determine tribological behavior. The tribological, physical and mechanical properties of the brake pads were measured and their friction surface morphology was explored via optical and scanning electron microscopy. Results showed that the Premix affected the friction coefficient. Moreover, it decreased the specific wear rate. The small value of friction coefficient is 0.566 at 90 °C whereas the small value of specific wear rate is 3.8 × 10−8 cm3/N.m at 180 °C. Friction and wear results approximated those of commercial brake pads. It was concluded that the Premix played a crucial role in the tribological, physical and mechanical properties of the brake pads.

Investigation of Caryota urens fibers on physical, chemical, mechanical and tribological properties for brake pad applications

The idealization of this research work is to extend the utilization of the naturally available fibers as a key ingredient in the development of a non-asbestos free brake pad. The fibers used in this work are Caryota urens, which is found all over the Asian regions and abundantly available. The compression molding machine was used to develop the non-asbestos free brake pad. The fibers were added in weight percentages of 5, 10 and 15. The various physical, chemical, and mechanical properties were evaluated. Chase test rig was used to evaluate the tribological properties. The combination of Caryota urens fiber with the barytes had a more significant influence on the tribological properties. The brake pad composites with ten weight percent of Caryota urens fibers based brake pads possessed a good coefficient of friction values with less fade values and less fluctuations. Increasing the weight percentage of Caryota urens fibers in the brake pad formulation had a decreasing trend in the wear performance but increased recovery properties.

Influence of benzoyl chloride treatment on the tribological characteristics of Cyperus pangorei fibers based non-asbestos brake friction composites

Natural fibers are widely used in the various lightweight and medium load applications due to their vital advantages. Cyperus pangorei is abundantly found on the river banks. The current study deals with the usage of Cyperus pangorei fibers that were retted using a manual retting process in the brake pad formulation. The fibers retted were treated with benzoyl chloride to enhance adhesion characteristics. The benzoyl chloride treated and untreated Cyperus pangorei fibers were used in the development of brake pads with other ingredients constant as per industrial practice. The developed brake pads were analyzed for its physical, chemical, thermal and mechanical properties as per industrial standards. The tribological performance of the brake pads was analyzed using a pin-on-disc tribometer as per ASTM G-99-05. It was proved that benzoyl chloride treated Cyperus pangorei fibers based brake pads showed excellent performance characteristics compared to untreated one due to better bonding with matrix causing good contact plateaus formations as confirmed from Scanning Electron Microscopy.

Effect on the Properties of Brake Pads of Recycling Dust as Filler

This research is focused on the effect recycling dust (RD) on properties and performance of brake pad composites. Recycling dust was produced from grinding process of in-finishing products to standard thickness and was used as a new friction material in brake pads. Based on a simple experimental formulation, the proper type of recycling dust reused in brake pad formula was investigated by changing recycling dust type in mixing process. In the experiment, the properties of brake pads, hardness, density, porosity, and Young’s modulus were measured. Furthermore, the morphology and composition of recycling dust will be characterized by X-Ray Fluorescence (XRF), and Scanning Electron Microscopy (SEM). The developed composite brake pad showed that the value of density and compressibility increased while the value of hardness and Young’s modulus decreased by adding 10wt% of recycling dust to commercial brake pad formulation. Hence, the benefit of this work is using recycling dust as one of alternative fillers in disc brake pad materials without compromising the quality and performance.

Tribological performance evaluation of fused mullite-reinforced hybrid composite brake pad for defence application

The current study deals with the replacement of existing sintered bronze brake pad using hybrid composite brake pads for armour vehicle application. In the present work, fused mullite was added in three different weight percentages which was compensated by synthetic barites. The pads were produced by conventional manufacturing procedure. The physical and mechanical properties were measured as per industrial standards. The tribological performance was evaluated using Chase test following IS2742 Part-4 standards. The test results showed that 3 wt% of mullite abrasive in hybrid brake pad formulation produced reduced density, less squeal, less frictional undulations with the minimum wear of 0.887 g for 100 brake applications. Worn surface characteristics were analysed using scanning electron microscopy.

Nanocomposite Kaolin/TiO2 as a Possible Functional Filler in Automotive Brake Pads

An automotive friction brake pad is a complex system consisting of several components with unique and balanced properties related to operation conditions. There are efforts to develop brake pads with longer lifetime and better friction performance and wear properties. Those properties are related to composition of the pads, and therefore, new materials are being evolved. Tuning the friction and wear properties can be achieved with the selection of a functional filler and optimizing its amount in a formulation of friction brake pad. Laboratory-developed and laboratory-prepared nanocomposite material kaolin/TiO2 (KATI) has been introduced to formulation of the commercially available automotive low-steel brake pad. Kaolin was utilized as a matrix for anchoring TiO2 nanoparticles. New unused pads and pads after AK master, a standard dynamometer testing procedure of friction performance, were investigated using light and scanning electron microscopy providing information on the structure and its changes after the friction processes. Moreover, MTK wear test was used to compare wear rate of the newly developed pad with the reference low-steel pad. Improved durability of the brake pad formulation has been observed together with sufficient friction performance. Microscopic analysis shown homogenous distribution of the KATI nanocomposite in the friction layer. From the obtained results, it can be assumed that the new formulation is promising regarding to the life cycle of the pads and reduction of wear rate and thus potential production of wear particulate emissions.

Characterization of Areva javanica fiber – A possible replacement for synthetic acrylic fiber in the disc brake pad

Areva javanica (AJ), a natural cotton flowers fiber of Amaranthaceae family was taken up for the study of its possible utilization in a friction composite. The chemical composition of Areva javanica fiber (AJF) such as cellulose, lignin, ash, moisture, wax content, and density was evaluated. In addition to these, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC) tests were performed. The surface roughness of AJ fiber was estimated using atomic force microscopy (AFM) and the statistical analysis using Weibull distribution was carried out to identify the diameter of AJ fiber. TGA studies revealed its moderate thermal resistance upto 219℃, and a density of 1.4005 g/cc was estimated of AJF. An attempt was made to make use of the AJF as a potential reinforcement material for acrylic fibers in an organic disc brake pad formulation. Upon fibrization, AJ fibrillates and forms a dense structure, a vital property required for the production of a brake pad. The role of AJ fiber in brake pad was studied by investigating the behavior of fibers from the mixing stage to the cured brake pad. Results revealed that the developed brake pad had a density of 2.01 g/cc, hardness HRS 91, Loss on ignition 21.68%, and cold and hot shear strengths of 44 and 27 kg/cm2, respectively. These values were very close to that of an Acrylic fiber based brake pad. The wear test using Friction Assessment and Screening test (FAST) gave the wear percentage of 0.0187 in3/Hp-h which was found to be 16% higher than AJF (0.0159 in3/Hp-hr) based brake pad.

Biological response of an in vitro human 3D lung cell model exposed to brake wear debris varies based on brake pad formulation

Wear particles from automotive friction brake pads of various sizes, morphology, and chemical composition are significant contributors towards particulate matter. Knowledge concerning the potential adverse effects following inhalation exposure to brake wear debris is limited. Our aim was, therefore, to generate brake wear particles released from commercial low-metallic and non-asbestos organic automotive brake pads used in mid-size passenger cars by a full-scale brake dynamometer with an environmental chamber simulating urban driving and to deduce their potential hazard in vitro. The collected fractions were analysed using scanning electron microscopy via energy-dispersive X-ray spectroscopy (SEM–EDS) and Raman microspectroscopy. The biological impact of the samples was investigated using a human 3D multicellular model consisting of human epithelial cells (A549) and human primary immune cells (macrophages and dendritic cells) mimicking the human epithelial tissue barrier. The viability, morphology, oxidative stress, and (pro-)inflammatory response of the cells were assessed following 24 h exposure to ~ 12, ~ 24, and ~ 48 µg/cm2 of non-airborne samples and to ~ 3.7 µg/cm2 of different brake wear size fractions (2–4, 1–2, and 0.25–1 µm) applying a pseudo-air–liquid interface approach. Brake wear debris with low-metallic formula does not induce any adverse biological effects to the in vitro lung multicellular model. Brake wear particles from non-asbestos organic formulated pads, however, induced increased (pro-)inflammatory mediator release from the same in vitro system. The latter finding can be attributed to the different particle compositions, specifically the presence of anatase.

Experimental study of the properties of brake pad using egg shell particles–Gum Arabic composites

This experimental study investigated the properties of eco-friendly (biodegradable) brake pad using egg shell (ES) particles and Gum Arabic (GA) as the binder in order to replace asbestos and formaldehyde resin which are carcinogenic in nature and not biodegradable. The brake pad formulation was produced by varying the GA from 3 to 18 wt%. The following properties were tested: wear rate, hardness values, compressive strength, thickness swelling in water and SAE oil, thermal resistance and specific gravity. The microstructure of the brake pad showed that fair bonding was achieved with the formulations from 15 to 18 wt% of GA. The sample with 18 wt% of GA in ES particles gave the best properties. The temperature of maximal decomposition of ES particles was higher than asbestos and many agro-wastes currently used in the production of brake pad materials. The results obtained at 18 wt% of GA in ES particles formulation compared favourably with the commercial brake pad. Hence, the developed brake pad can be us...

Optimization of tribological properties of cement kiln dust-filled brake pad using grey relation analysis

Cement kiln dust (CKD) filled with different resin (straight phenolic, cashew nut shell liquid (CNSL) modified, Linseed oil modified, Alkyl-benzene modified) based brake pad formulations were fabricated and characterized their physical, mechanical and tribological properties. Tribo-performance of the fabricated brake pad formulations were evaluated on a Krauss type friction tester as per the ECE R-90 (Economic Commission for Europe Regulation-90) norms. The experimental results indicated that CKD and straight phenolic resin combination were proved best in terms of coefficient of friction, friction stability, and friction fluctuations, but inferior in wear performance and counterface friendliness. The combinations of CKD and CNSL/Linseed oil modified resin were most beneficial for enhancing both recovery and wear performance as well as reducing variability in friction. The formulation with CKD and Alkyl-benzene modified resin was observed the best fade performance and counterface friendliness. The results obtained were considered as criteria and grey relation analysis (GRA) approach was used to determine the complete ranking of the brake pad formulation. The results also concluded that the formulation of CKD with straight phenolic resin exhibits the optimal properties.

Tribological screening tests for the selection of raw materials for automotive brake pad formulations

A modified pin-on-disc test was applied to determine tribological properties of typical brake pad constituents. Ball-milling of these ingredients together with iron oxide and graphite provided model materials displaying the main features of real third bodies. Solid lubricants like graphite affected the friction and wear behaviour of Fe3O4 powders considerably whereas further addition of hard nanoparticles induced only minor effects. This was corroborated by comparison with modelling results. MoS2 played a dual role. Depending on special conditions, this ingredient either reduced or increased friction. The latter could be explained, after nanoscopic characterization, by oxidation and destruction of the wear-protecting tribofilm.

Effect of varying cashew dust and resin on friction material formulation: stability and sensitivity of µ to pressure, speed and temperature

Inconsistent friction level during braking at different speed and pressure is a major concern to the brake pad/lining manufacturers as it is proven to be a formulation dependent. The behaviour of friction of an NAO brake pad is highly complex under a set of dynamically variable pressure speed and temperatures. This paper examines the sensitivity of friction (μ) towards braking pressure and sliding speed. Normally, the organic components burn off at elevated temperature, reducing the brake effectiveness and hence its temperature sensitivity is also carried out by fade test. This paper discusses the effect of organic components, namely resin and the cashew friction dust in a disc brake pad formulation. Three pads with varying resin (10.11, 11.11, 12.11 percentage by weight) and the cashew dust (9.33, 10.33, 11.33 percentage by weight) are fabricated and their effect in relation to stability of friction is studied by carrying out the test on the inertia dynamometer following JASO C 406 schedule. Optimisation of the ingredients is carried out using the response surface methodology. It is observed that composites with 10.11% resin and 9.33% cashew dust resulted in better performance with consistent friction level viz. least sensitivity of μ to operating variables, namely speed and pressure by carrying out a regression analysis.