UPM BioMotion^™ Renewable Functional Fillers – Sustainability boost for an entire industry

Sustainability is a key challenge for all manufacturers of rubber and plastic components, because of regulatory challenges, pressure from financial markets, and customer wishes. Hence, new and effective ways to reduce the carbon footprint in production and final articles are being sought throughout the industry. UPM's new RFFs are leading the way by making it easy to replace fossil materials with renewable materials in end-use applications. They increase the share of renewable raw materials in elastomer, thermoplastic, and TPE-based products by up to 50%. In combination with other bio-based raw materials, the renewable share in the end products can be further increased.

UPM BioMotion™ RFFs offer rubber compounders and producers of mechanical rubber goods a perfect solution to meet their sustainability goals. The Renewable Functional Fillers contain at least 94% biogenic carbon (certified by DIN CERTCO) and have a carbon footprint of more than 90% lower than standard industrial carbon blacks with further upsides in near future, which may even result in a significantly negative carbon footprint (see Figure 1). Compared to traditional functional fillers, the density is more than 25% lower. Like white, inorganic fillers, and unlike industrial carbon blacks, they are 100% electrically insulating and free of polycyclic aromatic hydrocarbons (PAH) (see Table 1).

The high purity makes RFF-based products particularly interesting for food contact and drinking water applications. The relevant approvals for use in this sector are currently being prepared. Even though RFFs define a new class of materials based on natural raw materials, they are on the same high-quality level as fossil-based fillers. This is possible because UPM uses only hardwood (beech) for production, which means that the composition of the raw material is very constant. In addition, strict process controls and a rigorous quality assurance system ensure the highest material consistency.

UPM BioMotion™ RFFs are currently produced at a pilot scale of several 1000 kg which allows material testing and application development activities in elastomers, thermoplastic elastomers, and thermoplastic compounds from lab to industrial scale with various key partners. The pilot process will be directly scaled to industrial size in UPM’s state-of-the-art biorefinery which is currently under construction in Leuna, Germany. The biorefinery will produce a broad range of wood-based biochemicals. The total investment of the project is €550 million and the scheduled start-up will be in late 2023 with a total production capacity of 220 000 tons.

UPM BioMotion™ is currently available in three different material qualities positioned in the low to medium reinforcing range suitable for premium rubber, TPE and plastics applications. They differ in their specific surface area and range from approx. 10–40 m²/g (see table). The RFFs are all granulated and have significantly less than 3% moisture content (see Table 2).

Case study: UPM BioMotion™ RFFs for automotive weatherstrips

The benefits of UPM BioMotion™ RFFs can become strikingly clear when applied to a complex product such as a vehicle. OEMs are actively seeking more sustainable components. The challenge for automotive manufacturers is how to strike a balance between good technology and environmental performance. This is where UPM's renewable functional fillers can significantly contribute, as in the following example of a door profile (see Figure 2).

The automotive industry has started replacing heavy steel parts with light metals to increase the range of vehicles and further reduce CO₂ emissions per kilometer traveled. Switching to aluminum or magnesium for car doors, for example, allows a weight reduction of 50–75 %, which can lead to an overall weight saving of more than 40 kilograms per vehicle. However, both metals suffer from electrochemical corrosion when used with steel, requiring non-conductive vehicle seals with 10⁹ Ohm*cm and higher electrical volume resistances. [4, 5]

The raw materials traditionally used in these applications pose significant challenges for compound developers and automotive weatherstrip manufacturers in meeting these new requirements without compromising compound processing, rubber properties, environmental footprint, or product weight. One possibility, for example, is the use of industrial carbon blacks in combination with large quantities of heavy white fillers. However, this approach is generally viewed rather critically, as it counteracts OEMs’ efforts to reduce weight and lower their carbon footprint.

The potential of renewable functional fillers for application in automotive weatherstrips is demonstrated by five rubber compounds (see Table 3), which differ in the filler systems used. These allow the evaluation of fundamental compound properties and trends when replacing industrial carbon blacks with UPM BioMotion™ in an EPDM model formulation. These are explicitly not final optimized blend formulations. The strategies applied show the first possible ways of using the RFFs, which can also be transferred to other elastomer systems. In addition, a multitude of further combinations and the adaptation and exchange of other compound components are possible. Compounds No. 1 and No. 2 (see table "Overview of the EPDM rubber compounds investigated") each use an industrial carbon black in combination with a white filler, and each serves as a reference. In compound No. 3, the industrial carbon black was replaced by UPM BioMotion™ X40 in the same weight ratio. In blend No. 4, the white filler was omitted, and the oil quantity was reduced by 33%. In compound No. 5, a combination of industrial carbon black and renewable functional filler was tested in a ratio of approximately 25/75.

All blends were prepared using a laboratory kneader in a two-stage process. In the first mixing stage, the rubber, fillers, plasticizers, drying agents, and processing agents were kneaded together for a total of five minutes. In the second mixing stage, the accelerators and sulphur were added to the basic mixture, and everything was mixed for a further two minutes. The mixtures were then cured at a temperature of 160°C according to their t90 time plus an additional five minutes. Physical testing was carried out using standardized test procedures: hardness (ASTM D2240), tensile properties (ASTM D412), compression set (ISO 815-1, 24h at 70°C), density (ASTM D297), and volume resistivity (ASTM D991) (see Table 4).

Compounds No. 1 and No. 2 demonstrate the dilemma of the automotive profile industry today. The specific volume resistances of 10⁹ Ohm*cm required to prevent electrochemical corrosion effectively are not achieved in either case. This requires either a reduction in industrial carbon black or an increase in the white filler content. While the former approach typically has a negative effect on processing behavior, the latter strategy leads to a significant increase in the compound density and thus the final component density, which contradicts car manufacturers’ striving for further weight reductions. This is not the case when renewable functional fillers are used. Each of the blends Nos. 3, 4, and 5 exceeds the required electrical conductivity targets by orders of magnitude, with an additional reduction in material density of 7–15% compared to the reference blends. In addition, the UPM BioMotion™ compounds are characterized by a very high share of renewable material in the range of 31–40%, which is also reflected in the final carbon footprint of the mixes. The examples shown have 31–48% lower GWP compared to the state of the art.

And that is only the beginning! On the one hand, RFFs will soon be significantly CO₂-negative through continuous improvements in production. Furthermore, the renewable share can be increased even further through compound optimisation. Depending on the exact compound performance, 100% substitution of industrial carbon black by UPM BioMotion™ RFFs is already possible today in specific applications. And their use together with other renewable raw materials, such as bio-based rubbers and process oils, is also possible without any problems.

RFFs make cars more sustainable

Combined with the weight savings from switching from steel to Al/Mg in the doors, UPM BioMotion™ enables a huge potential to save further CO₂ during the car's use phase. A lighter vehicle is always more efficient, regardless of whether it is petrol, diesel, or electric. Vehicle weight directly impacts fuel consumption, so a lighter weight improves overall fuel efficiency and significantly reduces CO₂ emissions. For example, a 10 kg reduction in the weight of a petrol-driven passenger car leads to a reduction in CO₂ emissions of up to 1 g/km. [6]

The combination of light metal doors and RFF-based automotive weatherstrips can easily lead to a weight saving of 40 kg or more. If we now take the average use phase of a car in Europe of approximately 200,000 kilometres as a basis, the emission of approximately 800 kg CO₂ per car can be avoided. That this is a significant reduction becomes apparent when looking at the sheer number of vehicles. For example, there were about 48 million in Germany alone in 2021, which would correspond to a total reduction of over 38 million tonnes of CO₂ or a saving of over 100 million barrels of crude oil. [7] And automotive weatherstrips are just one possible application for UPM BioMotion™. Current knowledge suggests that it can be used in principle in all rubber and plastic components, including those outside the automotive industry, and is particularly valuable when sustainability is paramount.