35 years rethinking solutions
35 years improving tomorrow
35 years encouraging eco-efficiency
35 years driving excellence
Case studies / Friction
Bismuth sulfides, the new contenders against strong LME dependent metals?

Spoiler, they are! Despite the current circumstances, the increase in volume production of Bi metal divided it’s base price times 3 and stabilized there, making its usage feasible for the friction industry.

After a big drop in the consumption of commodity metals, (such as copper, tin, aluminium, among others), as a consequence of a global pandemic,  it is expected base metals markets to return to normality in 2021, supporting increases in prices, as the world economies start to pick up.

This situation has brought a significant unbalance between demand and production capacity. In 2021, the demand-side will be also supperted by an increase of spendings of governments around the world, primarily through investment in infrastructure projects, driving increases in base metal prices. This is one of the main causes for the price rise in many raw materials but also in unexpected hassles to stock up from several raw materials.

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!

Chemical properties
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.
AKM Critical sections
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.
Disc roughness
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.
Pad wear
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

Friction
Go back to friction case studies
back to all case studies
see friction products
Stay updated! Subscribe to our newsletter and receive monthly updates about the future of the industry






    Contact us
    We would love to talk about your next project

    Do not hesitate to contact us for any question or requirement you may have. We will be happy to collaborate with you

    Visit us

    Armenteres s / n – Pol.Ind. MATACÀS- Nave 21 08980

    Sant Feliu de Llobregat Barcelona, Spain

    Call us

    +34 93 666 46 11 / +34 635 519 002

    Write to us

    friction@rimsa.com

    Or leave us a message and one of our agents will contact you






      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 inflection point came when concerns over lead toxicity paved the way towards the evolution of bismuth replacing lead for a variety of applications.

      Several of the new applications in free machining steels, lead free solders and galvanizing had the size and potential growth to put intense pressure on demand for bismuth, and of course they did!

      Searching on ECHA the CAS Nº for bismuth on its metal form, as well as for its sulfide (Bi2S3) and its derived oxide (Bi2O3) “No hazards have been classified”, and so, applications for this metal increased even more. In fact, it is currently being used in large scale on fine electronic components, antibacterials, tissue engineering, biosensing etc.

      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!

      Friction
      Go back to friction case studies
      back to all case studies
      see friction products
      Stay updated! Subscribe to our newsletter and receive monthly updates about the future of the industry






        Contact us
        We would love to talk about your next project

        Do not hesitate to contact us for any question or requirement you may have. We will be happy to collaborate with you

        Visit us

        Armenteres s / n – Pol.Ind. MATACÀS- Nave 21 08980

        Sant Feliu de Llobregat Barcelona, Spain

        Call us

        +34 93 666 46 11 / +34 635 519 002

        Write to us

        friction@rimsa.com

        Or leave us a message and one of our agents will contact you