Case studies / Friction
Bismuth sulfides the new contenders against strong LME dependent metals?
Spoiler, they are! Despite the current circumstances, the increase in the production volume of metallic Bi has divided its base price by 3 and has stabilized at that level, making its use viable for the friction industry.
The industry has evolved, and so we did! Since we were the rookies of the friction industry 35 years ago, a lot of product families were developed besides copper, brass and bronze, such as synergistic composites, abrasives and synthetic metal sulphides. But we couldn’t limit to have a wide range of products! We want to be a trustworthy partner for our customers, and so, we decided to move the focus from the product, to the solution.
Now the important is the purpose of the product, more than the origin. And to do so we have to be aware of which are the main challenges of the industry, where the industry is moving forward and so, how can our products can adapt to our customers’ needs.
But we cannot shoot to the air, we need to have some criteria on our product development strategy. Therefore, we need to give an answer to the three main axes that drive where the industry is moving forward.
Therefore, moving some consumptions to products with more stable trends and less LME dependency became a new driver in many industrial fields.
Base metals — such as iron ore, copper, aluminum and nickel — are listed in stock markets. Beyond supply and demand, the quotation in the stock market is the third factor influencing the short-run fluctuations in commodity prices.
Prices of strategic metals for friction industry, such as tin and antimony present pronounced variability both at short and long term, even though its demand has been continuously increasing during the 21st century. Meanwhile, unlike other metals, the base level price of bismuth has been largely reduced during the last decade and it’s pretty stable. Bismuth is not listed in stock markets.
Bismuth is a remarkable eco-friendly metal despite its location on the periodic table
Scientific literature concurs that bismuth and most of its compounds are less toxic compared to other heavy metals (lead, antimony, etc.) and so, the inflection point came when several industries realized about that and started to massively replace lead on a wide range of industries. Although bismuth had few commercial applications at the beginning of the century, which made this product very expensive in the past, it, new applications followed afterwards.
Therefore, since then, new applications followed afterwards. And now we stretch a bit more the focus on the friction industry and realize that some commonly used products, have now a serious contendant, which not only is able to provide a similar effect, or even an improvement, but also it is reaching its price level, if it has not already done so.
If we target some of the “top environmental challenges” of nowadays, as it is antimony replacement (Sb2S3) or reducing tin dependency, we can analyse if its analogue in bismuth (Bi2S3) has potential to replace them. Results turned out positive in this regard and that’s why this product is already being used for the most advanced friction material manufacturers from a technical perspective, and of course at rimsa we are ready for it!
To begin with, Bismuth (III) sulfide is isostructural with antimony (III) sulfide and both crystallize in an orthorhombic structure. Bi2S3 has also a close oxidation temperature range, to Sb2S3 and tin sulfides. Also, its reaction mechanism with oxygen is the closest one to antimony trisulfide.
Therefore, because they all share a very similar chemistry, they behave similarly when included in a friction formula. As these sulfides have a very similar interaction mechanism with the phenolic resin, if we take a look on the high temperature sections of the AKM test, we’ll see they provide the same capacity of reducing the CoF amplitude and reducing the in-stop variability, which will have immediate consequences on the NVH properties of the overall formula.
It has been observed that the distinctive effect of Sb2S3 is its ability to achieve a very smooth finishing on rotors compared to other established additives. Bismuth-based sulfides, are able to reduce the disc rugosity, with comparable values to tin sulfide as well.
Besides cutting the cost of tin sulfide in half, bismuth sulfides are able to achieve similar wear rate on the pad.
At rimsa, pure (BI81) and composite (BI65) compositions are available, to match the requirements of your application. BI65 was designed to reduce the density of the product, and therefore its price. It’s unique composition provides the same friction behaviour with an additional contribution of thermal conductivity.
Thanks to our production technology, we ensure consistent quality and very stable chemical composition, without impurities and free of heavy metals
These are the products used in this case, go take a look at its specs
Case studies / Friction
SF range: Substitution of tin sulphides through modification of oxidation properties of synthetic sulphides
The use of composite sulfides with a particular microstructure allows to reduce the content of Sn without compromising safety and wear
Tin sulphides are widely used by OE manufacturers. However, the high content of tin makes them very expensive and LME dependent.
The use of synthetic metal sulfides has been seen as one of the solutions for stabilization of coefficient of friction at high temperature and reduction in wear in copper-free formulations. Metal sulfides are converted in metal oxides during the braking, and this oxidation reaction affects the tribochemistry in the interface between pad and rotor. The study of the relationship in between the oxidation temperature of different metal oxides and the effect of those sulfides in the performance and wear of a copper-free formulation can help to bring a better understanding of the mechanism that makes the sulfides a good solution for copper-free formulations.
Our research has demonstrated that two sulfides of identical chemical composition can have different reactivity in front of oxygen and provide different degree of performance and wear protection. As a result, we developed our SF range of Iron /Tin sulphides Composites, which are not just mechanical mixes of different sulphides. Their unique microstructure allows us to modify the oxidation temperature compared with a mechanical mix of FeS and SnS of the same chemical composition.
With this change, we can get closer to the oxidation temperature of tin-only based sulphides, but reducing the content of tin and so the price level. Phenolic resin is the matrix of the brake pads and starts to decompose around 300ºC, in presence of oxygen and temperature, resulting in the degradation of the PAD surface. Our objective is now to confirm that there is an interaction between metal sulphides and resin, and the oxidation mechanism of both materials seems to be modified when they are blended.
Comparative AKM test have been done to correlate the differences on oxidation temperature range with the friction performance in a NAO Cu-free friction material. SF series is a new option with improved cost-to-performance ratio. SF05 is recommended to replace SnS based compounds and SF10 and SF13 are recommended to replace SnS2 products. Please, contact us for more information.
Talent wins games, teamwork & intelligence win championships
Our multidisciplinary team includes tribologist, chemists and logistics experts. More than twenty years of experience and great knowledge of the market and applications allow us to support during all phases of the project, guaranteeing the quality and flexibility that the sector demands.
Case studies / Friction
LM09: Replacing Sb2S3 without busting the bank
LM09 is a synergistic composite designed to replace the dangerous antimony trisulfide in brake pad applications with minimum need of testing and reformulation.
– LM09 is designed to provide high thermal conductivity to the pad
– LM09 keeps the performance at high temperature and reduces wear
– Can be used in all kinds of formulations. It helps build a stable transfer layer on PAD and ROTOR
– Particle size distribution made it suitable for easy mixing and dispersion, and make it suitable for standard storage.
Tested in a NAO type, copper-free formulation in replacement of Sb2S3, in volume, LM09 achieves a thin and homogenous transfer film on the pad surface, contributing to the stability of coefficient of friction and low wear in both pad and rotor
Several studies reveal that occupations closely related to antimony have been more prone to cardiac diseases, skin irritations and digestive disorders.
Moreover, Sb-subproducts has been reported to be partially soluble in physiological fluids and carcinogenic in laboratory animals, though for human beings is still under suspicion
Check the products related to this case study
Case studies / Friction
Where are we coming from? From Asbestos-based to NAO Copper-free
A joined effort among manufacturers, regulatory organizations and the automotive industry has brought a noticeable evolution on the composition of the friction materials
All machine in movement needs to be stopped at some moment. The brake is responsible to turn this kinetic energy into heat and release it through the interface.
This is the everlasting basis of the friction industry. Actually, during a normal braking, the disc is responsible to dissipate around 80 % of the heat generated by friction. The temperature can raise up to 600-700 ºC in rough conditions. As a result of the energy involved in this process, tribo-chemical reactions and erosion always take place.
The chemical composition of the brake PAD then, is directly related with the performance of the whole brake system.
Every time you stop your vehicle, a small amount of material is released in form of PM10 and PM2,5, small enough to be caught in air turbulence and easily enter human airways.
Depending on their composition, can be quite harmful to wildlife as they might contain metals such as copper, chromium, lead, antimony and metal oxides.
Considering that around 21% traffic-related PM10 emissions come from brake wear, automotive industry, raw material manufacturers and regulatory organizations have a shared responsibility to follow up dust emissions released during braking, and come up with innovative solutions to overcome this environmental threat.
At rimsa we were pioneers on manufacturing lead-free brass and bronze chips 20 years ago
On the other side, recyclability regulations in the latest 1990´s for vehicles in Europe (End-of-life directive 2000/53/EC) states a maximum content of metals such as Pb, Hg and Cr(VI) <0,1 %. and Cd <0.01 %. Friction materials were a source of Lead. It was common to use lead sulphide as lubricant and lead derivatives were regular contaminants in natural products such as pyrite (natural FeS2), sometimes up to 10%.
Since more than 20 years ago, our unique manufacturing process enables us to offer the OE’s choice of lead-free CHIPS with the best value-for-money.
Case studies / Friction
REACH changes its normativity on the labeling and SDS of brass containing Pb
As of January 5, 2021, manufacturers/distributors on the EU market of brake pads will not only to notify downstream customers of the presence of SVHCs but ECHA itself as well if it contains a whole contain > = 0.1 % Pb (SVHC)
Recycled brass chips & swarfs are produced during the mechanization of big brass pieces to obtain products such as decorative pieces, taps, balustrades, profiles etc.
These pieces must be machinable, otherwise it would be impossible to obtain the necessary shapes required on these fields. To do so, the standard alloy available in the industry contains 1 -3 % of Pb, as this metal improves its manufacturability.
So far, CLP considered that an alloy is considered a mixture, that, if it do not present any hazard to human health by inhalation, ingestion or contact with skin or the aquatic environmental in the form they are placed on the market, do not need CLP label.
What has changed is that lead, even in its massive form, as agreed in ATP09 at REACH Registration, if it is in a concentration 1-3 % it will contribute to the classification of the mixture with the following indications (which must be indicated on the label) :
At rimsa, we manufacture our own alloy on a unique completely dry process without including lead on the mixture
According to Law 8/2010, not labeling a product according to CLP (being aware of its dangers) is considered a serious offense, penalized with fines from 6.001 € to 85.000 €
Therefore, the alloy must be labeled with lead hazards and the SDS must be updated from June 2020, following the indications below:
- Our Brass chips are considered a MIXTURE, that contains lead, considered SVHC (Substances of Very High Concern).
- Brake PADS/Blocks/Linings are considered ARTICLES (products where shape, surface or design determines its function to a greater degree than does its chemical composition).
- As of January 5, 2021, manufacturers/distributors on the EU market of brake pads (articles) will not only have to notify downstream customers of the presence of SVHCs but ECHA itself if it contains a whole contain > = 0.1 % Pb (SVHC).
So, for those companies using the standard lead-containing brass in the industry, to avoid this new regulation, must remove this material from their formulations?
Obviously not, taking the lead from the mixture, all these companies will be able to continue using this fundamental product on so many formulations. But lead-free brass is not a standard on the industry and the well-known chopped lead-free brass wools become excessively expensive due to its manufacturing process
On the other hand, many other companies might consider to replace brass for a different material, and we want to be on their side too
Case studies / Friction
Controlling the degradation of the phenolic resin: The role of titanates on a friction material.
A clean PAD ensures the stability of its properties during its lifetime
To obtain a top-notch friction material, it is not enough to protect the phenolic resin. Indeed, it is a key parameter the control the performance and wear of the finished product. However, HOW this organic binder decompose is a crucial factor that will determine the comfort and the NVH properties of the pad. Can we control this? Let’s go deep on that.
We start from the fact that the mentioned phenolic resin transforms into a sticky substrate on the friction surface when it degradates. And, as if it was like a smoker/non-smoker lung, a cleaner surface will help us to avoid groan, noise and vibrations, while obtaining a smooth and stable braking. And how can we do so? The answer is on titanates.
TITAN series from TAM Ceramics are a cost-effective alternative to the common titanates available in the market that ensures ﬁbre-free morphology, avoiding health issues.
This way, we obtain a cleaner surface and so, when the counterpart contacts the friction material, we do not have that viscous residue between them which, as you might have guessed, will help us to reduce the CoF (μ) amplitude and improve μ stability, which are straightly related with the NVH and groan properties of a friction material.
Nowadays, there are a wide range of titanates with different morphologies and chemical compositions in the market. However, titanates commonly available in friction industry are a ﬁbrous product with health issues. To make them ﬁbre-free either the production costs are increased or they contain other metals on their composition.
On that lead, since 2019 rimsa has join forces with TAM Ceramics to tackle the challenges concerning this particular aspect of a friction material performance with innovative products specially developed for friction industry.
Case studies / Friction
Bismuth-based products not as rare as it is thought. Why now is the time?
In your opinion, which are the metals that are mostly used on friction materials nowadays?
Imagine we had the opportunity to do a massive survey asking this question to friction industry formulators.
They’d surely answer iron in first place, probably followed by copper, zinc, tin, maybe aluminium…But presumably not bismuth! It sounds quite an exotic metal, isn’t it? If you think this metal is more present in investigation laboratories rather than in industrial massive plants, you’d better leave the twentieth century behind and go deep in the environmental trends of 2020’s.
It is true nevertheless, bismuth had few commercial applications at the beginning of the century, and those applications that use it generally require small quantities relatively to other raw materials.
The increase in volume production of Bi metal broughts a drop on the prices, reducing the bismuth price to 30%
This immediate impact on the market made bismuth’s usage feasible for the friction industry. So let’s bring this back to reflect, while the price of metals such as tin and antimony increase and become more and more unstable, bismuth is doing the exact opposite, and there isn’t any forecast that sees this situation changing soon!
And now we stretch a bit more the focus on materials science
and realize that some products that have been commonly used such as antimony trisulfide or tin sulfides, and of course tin powder, have now a serious contendant, which not only is able to provide a similar effect, or even an improvement, but also it is reaching its price level, if it has not already done so.
And that’s why this metal is already being used for the most advanced friction material manufacturers from a technical perspective, and of course we are ready for it!
At rimsa, bismuth sulfide in pure (BI81) and composite (BI65) compositions are available, to match the requirements of your application. Thanks to our production technology, we ensure consistent quality and very stable chemical composition, without impurities and free of heavy metals. And yet are more bismuth-based products to come!
Case studies / Friction
Different strategies to remove copper from existing formulations
What started many years ago in the political corridors in the US, has risen as a priority project for almost all material development laboratories across the globe
Being automotive such a globalized industry, a concern that has sprung up on a specific market, can quickly become into a worldwide trend if it is properly justified by a greater good.
A clear example of it can be seen on the friction industry. What started many years ago in Washington and California, when copper considered as main cause for the extinction of salmon and rainbow trout, due to its neurotoxic behaviour in fish , has become into a priority project for almost all material development laboratories across the globe. Nevertheless, even there are still some grey areas to clarify, it is clear that the main brake system & vehicle manufacturers are already requiring copper-free formulations.
Friction industry is going on this lead but that’s not an easy job, as not a single solution has emerged as direct replacement for this material with unique properties. Engineers and friction material formulators must come up with new strategies to replace this non-ferrous metal if they want to stay on the run.
We are glad that so many companies have been able to develop their own Copper-free materials by using rimsa’s enviroLube as their key additive. Why so?
Finally, other companies have opted to create new copper-free formulations either by reformulating an existing copper-containing mix or creating a new one.
The key point to achieve a balanced formulation goes through being able to create a stable transfer layer while protecting phenolic resin from degradation in order to protect the integrity of the whole friction material.
The high heat dissipation capacity of copper combined with its ability to create primary plateaus makes impossible to find a direct replacement. So, if there is not a harmonized solution, there’s at least a successful strategy to address this challenge?
Case studies / Friction
What is polyacrilonitrile (PAN)?
Polyacrylonitrile is the most common precursor used to make carbon fiber.
Polyacrylonitrile (PAN) is a synthetic resin prepared by polymerization of acrylonitrile.
It belongs to the important family of acrylic resins and is a tough and rigid thermoplastic material that, resistant to most solvents and chemicals, burns slowly and has a low permeability to gases.
Fibers obtained by precision cutting in a wide range of cutting diameters and lengths are used for REINFORCEMENT in a wide variety of industrial applications. These include the manufacture of adhesives, castings, composite materials (“composites”), filters, acid battery plates, paints, paper, sealants and refractory materials.
It is considered an added-value polymer as, besides of reinforing the application where it is included, this material has intumescent behaviour (fire protective) and several studies reveal an increase of the matrix-fibre union strength compared to other traditional fibres on mortars and pavements.
Case studies / Friction
The green alternative to the alumina industry
Roots from plants can absorb the ionic species of metals such as aluminium in acid soils
Al2O3 is a standard abrasive used in friction materials to increase the coefficient of friction and keep clean the rotor surface. It derives however in aluminium contamination when in service, aluminum oxide is released to the environment. Roots from plants can absorb the ionic species of metals such as aluminium in acid soils, which has a clear environmental impact, including the growth of these plants due to the bioaccumulation capacity of this element. Furthermore, there are also articles suggesting a possible connection between the increase of the concentration of Al3+ ions in the environment due to human activity and some neurotoxic diseases in human beings
At rimsa we dedicate all our efforts to ensure excellent quality in each of our products and services, guaranteeing the satisfaction of all customers.
We guarantee the highest quality standards
Having made the recycled product the base of our initial growth, our objective is to ensure that the raw material received and the intermediate product are properly analyzed and obey the specified parameters in order to guarantee a homogeneous final product, which complies not only with the specification, but ensure stable performance.
Regarding the products that we commercialize, the selection of suppliers is essential. From rimsa we guarantee compliance with the specifications before each shipment, with a specific control plan.
Characterized by an excellent Quality Management System
Case studies / Friction
The seamless ally for lead removal in railway industry
Railway brake blocks are one of the most complex branches of the friction industry
Engineers and designers must come up with formulations balanced in several characteristics:
– LOW SQUEAL: Due to the high impact involved in railway applications
– HIGH HEAT DISSIPATION CAPACITY: Due to the high energy involved in railway applications
– WEAR AND CORROSION RESISTANCE: To reduce wear rate and increase the service life of the blocks
– LIGHT WEIGHT: And stable friction coefficient
– ACCEPTABLE COST: Versus performance