The most basic difference between an electric vehicle (EV) and internal combustion engine (ICE) tyre is that the former demands lower rolling resistance, quieter tread patterns and higher load bearing capacity. While there have been innovations within the tyre industry to meet the current demand for EV tyres, at the molecular level, research and development continues to achieve enhanced compound efficiency as tyre mixtures are complex.

As electric vehicles redefine performance benchmarks, tyre technology is undergoing a molecular-level overhaul. While the industry has focused on rolling resistance, noise reduction and load capacity, Japan’s Kuraray is pushing the boundaries deeper into the chemistry of rubber itself. By integrating silane-functionalised liquid rubbers into natural rubber-silica systems, the company aims to resolve longstanding formulation challenges. These innovations not only offer measurable improvements in abrasion resistance and wet grip but also open the door to broader adoption of sustainable materials in EV tyres. Kuraray’s work signals a strategic shift towards more efficient, adaptable and environmentally aligned tyre compounds.

Japan-based chemicals manufacturer Kuraray has dismissed all odds to achieve a more efficient molecular chemistry in tyres with its silane-functionalised liquid rubbers. In an earlier issue, Tyre Trends had reported how the company’s silane-modified rubber marked a major leap in tyre technology as it enhanced polymer interaction within the tyre, especially in natural rubber and silica-based formulations.

Coming to the present, its silane-functionalised liquid rubbers offer the reduction of rolling resistance (RR) and the resulting compound shows excellent balance of low RR, abrasion resistance and wet grip performance.

Speaking to Tyre Trends exclusively on the development, Technical Service Engineer for Quality and Product Development Department, Elastomer Division, Kuraray Co., Naoto Takahashi, divulged, “We propose to incorporate natural rubber (NR) for silica-based PCR treads. NR is preferable for its high strength and from the viewpoint of sustainability. However, the combination of NR and silica has typically been considered unusual as compounds for PCR treads. One of the reasons is that NR and silica have poor interaction, which causes decrease of physical properties.”

“Our silane-functionalised liquid rubbers can react with silica in the mixing stage and with NR in the vulcanisation stage. Using this technology, NR or silica-based compounds have been proven to have an excellent balance of lower RR and competitive abrasion resistance and wet grip compared to typical styrene-butadiene rubber, butadiene rubber and silica compounds. So we believe it has the potential for EV tyres, which require these properties,” he added.

Furthermore, using silane-functionalised liquid rubber in tyre manufacturing offers several advantages. Firstly, it provides a plasticising effect during the mixing stage, leading to lower torque and electricity consumption.

Secondly, the improved rolling resistance itself contributes to the sustainability goals by extending the driving range of EVs. Long-range EVs significantly reduce carbon dioxide emissions compared to fossil fuel-powered vehicles. This helps mitigate global warming and other climate changes. In addition, EVs with extended range reduce the burden on charging infrastructure and promote efficient energy use. Less frequent charging means reduced strain on the power grid.

Additionally, the improved performance of NR and silica compounds sheds light on the utilisation of NR, which is a kind of sustainable material. “We believe this technology could expand the potential of NR. If you are considering using more NR in your products, then this type of liquid rubber could be useful,” added Takahashi.

MIXING THE MIXTURE

Typically, it has been said that conventional silane coupling agents have poor reactivity with NR. This is not the case for silane-functionalised liquid rubbers. The liquid rubbers react with silica at the mixing stage by hydrolysis and condensation, in the same manner as silane coupling agents. As a result, the silica would be surrounded by hydrophobic liquid rubber chains. This helps silica to disperse well in the rubber matrix.

In the subsequent stage of vulcanisation, the reaction of liquid rubber chains and NR occurs. This forms bonds between two types of rubbers, effectively resulting in reinforcement of silica-NR interaction.

“We believe that these mechanisms contribute to maximising the potential of NR and silica combination,” said Takahashi.

The molecular weight of rubber is another key factor in determining the characteristics of liquid rubbers, alongside the glass transition temperature and monomer components.

Explaining how the molecular weight range of Kuraray’s liquid rubbers affect its compatibility and performance in tyre applications, the executive said, “Our liquid rubbers’ molecular weight range is strategically positioned between typical plasticisers and solid rubbers, ensuring an optimal balance of enhanced processing and physical properties.”

“Each grade’s molecular weight is precisely controlled and tailored to specific purposes and applications. Generally, liquid rubbers with lower molecular weights offer superior compatibility with other ingredients, while those with higher molecular weights provide better physical properties. Interestingly, the viscosity of liquid rubber alone does not determine the processability of compounds. We are glad to support you in selecting the ideal grade of liquid rubber to achieve your objectives,” he added.

He also noted that liquid rubbers have a low tendency to bleed out as a plasticiser because of their higher molecular weight and ability to be vulcanised. The low migration property directly affects the life span of the tyres.

Additionally, the improved abrasion resistance compared to traditional plasticisers also offers the long-term liability of tyres. “Wear particle is one of the biggest issues in today’s tyre industry because it has been recognised that it has a severe impact on the environment. The new regulation to handle this matter has been under discussion for a long time. Our silane-functionalised liquid rubbers would offer the solution to these challenges,” noted Takahashi.

COMPETITIVE EDGE

One of the characteristics of the material is its narrow molecular weight distribution. This provides the benefit of suppressing reduced physical properties due to the low molecular weight fraction. Another is that it has functional groups grafted onto the polymer chain. These functional groups seem to have different reactivity compared to other types of modification.

These features have a positive effect on the storage stability and other performances as tyres. The company highlighted that it has already found that the material would not deteriorate so much for 1-2 years in a bulk container under air.

Besides, the silane-functionalised liquid rubber technology is applicable to various types of tyres including winter and all-season tyres, and high-performance tyres. It is particularly beneficial in improving the dispersion of silica fillers, reducing compound viscosity and enhancing overall tyre performance. This technology helps achieve a balance between grip, low RR and abrasion resistance, making it suitable for a wide range of tyre applications.

Considering the characteristics of the material, another application of this type of material is TBR. Most TBR tyres use NR and carbon black (CB) compounds with less or no oils. However, using silica in place of CB in TBRs is getting more and more attention to achieve the high level of rolling resistance and wet grip performance. Here emerges the problem of NR and silica combination. As mentioned above, the silane-functionalised liquid rubbers would act as the effective additive for these kinds of compounds.

Commenting on the role of the liquid rubbers in enhancing wet or ice grip performance on winter tyres, Takahashi explained, “We have two types of silane-functionalised liquid polybutadiene with relatively higher glass transition temperature (Tg) and lower Tg. Initially,

we only commercialised the former one. However, in response to customer demand, we have developed another grade with lower Tg and are now fully equipped to mass-produce.”

“Liquid rubbers with lower Tg provide flexibility to the compounds even at low temperatures, which is particularly beneficial for the ice-grip performance of winter tyres. This flexibility ensures that the rubber remains pliable and maintains good contact with icy surfaces, enhancing traction and safety. Since the compound Tg is also highly affected by other components such as solid rubbers, plasticisers and resins, we think that our product lineup with different Tg offers freedom of choice for users’ compound formulation,” he added.

MEETING DEMANDS

The company continuously spoke with tyre manufacturers during the development of its liquid rubber. “We have instruments in our laboratory for measuring not only compound properties but also tyre performances such as wet grip and abrasion resistance. This allows us to have close and detailed technical communication with our customers,” said Takahashi.

He added, “The wet grip performance is usually expressed by the value of tanδ at 0 deg.C as an index from the viscoelasticity measurement. But the actual compound’s grip performance often shows a different result from the viscoelasticity. We have equipment to measure the friction coefficient of compounds on wet and icy surfaces, allowing us to minimise the discrepancy between viscoelasticity and grip performance.”

Alluding to how the use of silane-functionalised liquid rubber in EV tyres aligns with current trends and future directions in tyre technology, he said, “We recognise the growing trend towards sustainability as well as the importance of reducing rolling resistance and wear particles. Here, we recommend using NR more to address these issues. While the combination of NR and silica may not be the conventional choice for PCR tread compounds, we believe that our innovative approach demonstrates the potential of this formulation. The use of silane-functionalised liquid rubber offers the excellent dispersion and reinforcement of NR and silica compounds, paving the way for the solution to address future challenges in tyre technology.”

Takahashi indicated that the silane-functionalised liquid rubber can play a role in reducing the carbon footprint of tyre production. The key driver, he explained, is a measurable drop in rolling resistance, which translates into lower fuel consumption for internal combustion vehicles and reduced electricity use in EVs.

The firm also highlighted its broader sustainability efforts, noting that its liquid rubber plant is ISCC Plus-certified. From this year, Kuraray has started producing sustainable materials under a mass-balance approach – an initiative that includes its latest silane-functionalised grades, though the product range is still expanding.

On managing cost-performance trade-offs, he acknowledged that liquid rubber typically commands a higher price than traditional plasticisers. However, the benefits tend to supplement the cost.

The company pointed to challenges like dispersing high-surface-area silica in tread compounds – an area where its liquid rubber grades can provide a processing advantage. It also emphasised the potential of NR and silica combinations, made feasible with its silane-modified products, as an example of how formulation innovation can justify the premium.

Kuraray’s silane-functionalised liquid rubber represents a critical inflection point for tyre formulation – technically and environmentally. By enabling stable silica dispersion in natural rubber and forming durable crosslinks during vulcanisation, it addresses both performance and sustainability imperatives.

While the cost remains a consideration compared to traditional plasticisers, the material’s added value, such as reduced energy use, lower rolling resistance and extended tyre life, could redefine return on investments calculations for manufacturers. Its compatibility with evolving regulations on wear particles and carbon footprint reduction positions it not just as an additive but as a strategic material. The challenge ahead lies in scaling adoption without compromising economic efficiency.

Apollo Tyres, one of the leading tyre manufacturers in the world, has added another feather to its cap, with its Hungary production plant bagging the International Sustainability and Carbon Certification Plus (ISCC+) certification.

The globally recognised ISCC certification is a voluntary programme that recognises companies for their sustainability and carbon reduction initiatives. Apollo Tyres, by achieving ISCC+ certification, has been recognised for not only meeting the stringent sustainability standards but also for its responsible production in the industry.

Apollo Tyres Secures Gold Medal In 2025 EcoVadis Sustainability Rating

As part of its commitment, the tyre maker continues to focus on monitoring and verifying sustainability practices across its processes and supply chain.

Rajeev Kumar Sinha, Chief Manufacturing Officer, Apollo Tyres, said, “This certification is an important step forward as we continue to integrate sustainability deeply into our operations. It aligns perfectly with our ambitious goal of incorporating 40 percent sustainable raw materials – including renewable and recycled input materials – into our products by 2030.”

Kraton Corporation, a global leader in speciality polymers and biobased solutions derived from pine wood pulping co-products, has published its 2024 Sustainability Report, ‘Innovating with Purpose’. The report showcases the company’s advancements in climate action, circular product innovation and value chain partnerships, reinforcing its commitment to sustainable solutions.

Key achievements include a 41 percent reduction in Scope 1 & 2 greenhouse gas emissions since 2014 and a 35 percent decline in emissions intensity. Kraton also maintained its EcoVadis Platinum rating for the fourth consecutive year and received the 2024 Nitto Supplier Sustainability Award. Strategic initiatives such as a Double Materiality Assessment and a USD 35 million investment in biorefinery upgrades at its Panama City facility further demonstrate Kraton’s sustainability leadership.

The company enhanced transparency by expanding life cycle assessment (LCA) data to cover nearly 90 percent of its product portfolio, helping customers evaluate environmental impacts. Additionally, Kraton launched a data excellence program to streamline ESG reporting and refine decarbonisation goals.

Aligned with GRI, SASB, UN Global Compact and TCFD frameworks, the report reflects Kraton’s sustainability pillars: Being Reliable Partners, Preserving Planet and Empowering People. These efforts underscore Kraton’s dedication to driving meaningful progress across its operations and industries.

Marcello Boldrini, Kraton Chief Executive Officer, said, “2024 marked a pivotal year in Kraton’s sustainability journey. We turned ambition into action, significantly reducing our Scope 1 and 2 emissions by 41 percent from our 2014 baseline and earned an EcoVadis Platinum rating for the fourth consecutive year. We accelerated our decarbonisation strategy, advanced biobased innovation and partnered with customers such as WJ Group and Henkel to help address global sustainability challenges. As demand for sustainable chemicals grows, our focus remains on developing the right solutions, fostering strong partnerships and cultivating the culture necessary to lead this transformation responsibly and competitively.”

Rogier Roelen, Kraton Chief Sustainability Officer, said, “We have established new processes to scale credible, data-driven sustainability across our business. In 2024, we enhanced our ESG reporting through a data harmonisation programme and completed a Double Materiality Assessment to better align with the Corporate Sustainability Reporting Directive (CSRD). We also expanded our Life Cycle Assessment (LCA) data to cover almost 90 percent of our product portfolio, providing customers with greater transparency into the environmental impact of our products. These efforts reinforce our ability to identify where we can make the most impact and support more informed, strategic decision-making.”

Murfitts Industries, the UK’s largest tyre recycling company, has unveiled plans for a state-of-the-art materials recovery facility at Michelin’s Stoke-on-Trent tyre plant. This groundbreaking initiative will transform end-of-life tyres into valuable resources while significantly reducing the site’s environmental footprint. The advanced recycling process will recover energy to power Michelin’s manufacturing operations, cutting annual CO₂ emissions by 1,500 tonnes. Additionally, the facility will produce high-quality recovered carbon black (rCB) and tyre pyrolysis oil (TPO), supporting sustainable material production.

Under the agreement, Michelin will supply Murfitts with 12,500 tonnes of discarded tyres annually – equivalent to 1.35 million car tyres. This capacity far exceeds local demand, with the plant able to process the equivalent of two tyres from every car registered in Stoke-on-Trent and Staffordshire. Slated for completion by late 2026, the facility will apply Murfitts’ proprietary pyrolysis technology at commercial scale, extracting reusable raw materials from tyres. The rCB will serve as a sustainable alternative in tyre manufacturing and other industrial applications, while TPO will be used in material production and alternative fuels, displacing virgin petroleum feedstocks.

Beyond material recovery, the process generates steam that will directly supply Michelin’s tyre-curing operations, replacing natural gas and further reducing fossil fuel reliance. Murfitts, which already recycles 20 million tyres yearly for applications like sports surfaces and road asphalt, continues to pioneer circular economy solutions – ensuring tyre-derived materials re-enter production cycles, closing the loop on waste. This collaboration marks a major step toward greener tyre manufacturing and resource-efficient industrial practices.

Mark Murfitt, Founder, Murfitts Industries, said, “We believe this plant could be a breakthrough in the life cycle of a tyre. It moves tyre recycling on from recovering energy and material for other uses to being able to feed it directly back into factories for new tyre production. Our core ethos at Murfitts has always been that end-of-life tyres are a valuable resource and we need to do all we can to maximise the use of the energy and materials within them. We have been developing our pyrolysis process for a number of years and our results now show we can produce material from end-of-life tyres which can perform better than the virgin equivalent for some applications. This plant will be a win-win for the tyre industry, the local and national economy and the environment.”

Christina Peloquin, Site Director, Michelin UK, said, “This is a really exciting project which reduces our environmental impact at the same time as helping us stay competitive by lowering our energy costs. The team has worked exceptionally hard on this project, and we’re looking forward to welcoming Murfitts to our Stoke-on-Trent site.”

Maria Röttger, CEO and President, Michelin Europe North, said, “At Michelin, we see every challenge as a chance to lead positive change – and end-of-life tyres are no exception. As shapers, innovators and pioneers of sustainable mobility, Michelin is committed to transforming the way tyres are handled at every stage of their life cycle. Through our deep expertise and forward-thinking approach, we are co-building a robust recycling ecosystem that redefines what has previously been possible. This project with Murfitts Industries is a powerful reflection of Michelin’s enduring commitment to sustainability and responsible leadership in the tyre and rubber industry.”

Evonik Industries will localise production of a key tyre additive in Shanghai, marking a strategic shift to enhance supply security across Asia amid growing regional demand.

The Essen-based company announced plans to establish the final production step of its POLYVEST ST-E 60 product at its Shanghai facility, with operations expected to commence by the third quarter of 2025. The expansion will significantly increase the global production capacity of silane-functionalised polybutadienes.

The move represents Evonik’s latest effort to strengthen supply chains and reduce dependency on European manufacturing for Asian markets. POLYVEST serves as a reactive plasticiser in tyre formulations and is also used in rubber compounds, adhesives, tyres, coatings, and sealants.

“This strategic investment will enhance our production capabilities and ensure that our customers in Asia benefit from improved supply security and shorter lead times,” said Dr Anna Maria Ickert, Head of Evonik Coating & Adhesive Resins. “In today’s environment, fostering independent supply chains and bringing our products closer to our customers is essential, enabling us to respond more effectively to their needs.”

The Shanghai expansion comes as global chemical companies reassess manufacturing footprints following supply chain disruptions experienced during the pandemic and ongoing geopolitical tensions. China remains a crucial market for speciality chemicals, particularly in the automotive and construction sectors.

Evonik’s decision reflects broader industry trends towards regionalisation of production, with companies seeking to reduce logistics costs whilst improving responsiveness to local market demands. The tyre industry, a key end-market for POLYVEST, has experienced robust growth in Asia driven by expanding automotive production.

Dr Jürgen Herwig, Head of Evonik’s polybutadienes and speciality acrylics business, emphasised the expansion’s strategic importance. “This expansion aligns with our long-term strategy to strengthen our global footprint while maintaining a strong focus on sustainability and operational excellence,” he said. “The new capacity will enable Evonik’s customers to achieve their business goals while participating in the region’s growth.”

POLYVEST products utilise rubber-based chemistry to ensure compatibility with tyre tread compounds, thereby addressing performance requirements in an increasingly demanding automotive market. The localisation strategy aims to reduce lead times whilst maintaining product quality standards.