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.

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Kraton Corporation, a leading global producer of speciality polymers and high-value bio-based chemicals derived from pine wood pulping co-products, has achieved International Sustainability and Carbon Certification (ISCC) PLUS for its manufacturing facility in Panama City, Florida, United States. This independent certification tracks sustainable materials via a mass balance approach. The achievement allows Kraton to issue a formal ISCC PLUS Sustainability Declaration with shipments of its biobased polyterpene resins, providing its customers with the documentation needed to validate the renewable content in their own products.

The Panama City site becomes the company’s fourth production plant to gain this certification, building upon a commitment that started with the certification of its Sandarne, Sweden, facility in 2021. By securing these certifications across its network, Kraton strengthens its leadership in supplying circular and renewable solutions. This effort supports broader industry shifts, as customers can now more seamlessly integrate verified, sustainable materials into their supply chains and end products.

Ultimately, the company’s pursuit of such certifications aligns with a larger transition towards a more sustainable and circular economy, demonstrating how specialised chemical producers can enable tangible environmental progress through verified chain-of-custody systems.

Lana Culbert, Kraton Pine Chemicals VP of Marketing, said, “Our SYLVARES™ and SYLVATRAXX™ brands feature a portfolio of high-performance polyterpene resins. They are widely recognised for their use in adhesives and tyre applications, yet their versatility extends to other industries, like agriculture, with more opportunities ahead. While we can measure bio-based content of our pine chemicals using Carbon-14 analysis, certifying our Panama City facility under ISCC PLUS strengthens supply chain transparency, supporting the growth of the circular economy.”

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Solvay has inaugurated its new bio-circular silica facility at its plant in Livorno, Italy, a strategic investment that underscores Italy’s industrial leadership in green innovation. The facility directly anticipates evolving EU sustainability rules for tyres and supports the ambitious environmental goals of Solvay’s customers. By establishing this operation, Solvay positions itself as a proactive partner in achieving the objectives of the European Green Deal and upcoming product regulations.

The site manufactures highly dispersible silica using an innovative process that transforms rice husk ash, an agricultural byproduct, into a valuable bio-based raw material. This method creates a local circular economy, benefits the agricultural sector, and reduces associated CO₂ emissions by 35 percent compared to conventional production.

This initiative is a cornerstone of Solvay's global strategy to transition all its silica production to certified circular raw materials by 2026. While the Livorno site is the first to use rice husk ash, other global plants will utilise different local waste streams. For the tyre industry, adopting this circular silica already enables tyres to contain up to 15 percent recycled or renewable content, providing significant progress towards the sector’s 2030 material targets.

Beyond compliance, the silica produced is essential for developing energy-efficient tyres that lower rolling resistance, thereby reducing fuel consumption and extending electric vehicle range. The Livorno facility thus reinforces Solvay's market leadership in sustainable silica and highlights Italy’s vital role in the company’s broader portfolio of green investments, including projects in green hydrogen and circular soda ash.

Philippe Kehren, CEO, Solvay, said, “By acting now, Solvay is helping tyre manufacturers prepare for future EU requirements and meet their own sustainability goals. Livorno is a tangible example of how we turn circular economy principles into industrial reality, enabling progress for generations.”

Jana Striezel, Head of Purchasing at Continental Tyres, said, "Solvay has managed to transform an agricultural byproduct into a high-performance material on an industrial scale. We are looking forward to integrating more and more rice husk ash silica as a recycled material in our tyre production and are very satisfied with its performance. We are keen on innovative, renewable and recycled materials because they support our ambitious sustainability roadmap.”

An Nuyttens, President of Solvay’s Silica business, said, “Livorno sets a benchmark for circular innovation in Europe and beyond. Our goal is clear: wherever Solvay produces silica, we will integrate circular materials to reduce environmental impact and support our customers’ sustainability objectives.”

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Ecolomondo Corporation, a Canadian developer of sustainable technology for recycling scrap tyres, has announced that its Hawkesbury facility reached a key operational milestone during the week of 12 January 2026, by successfully completing a record five double processing batches. This progress signifies a major step forward as the company advances towards full commercial production at the plant. Utilising its proprietary Thermal Decomposition Process (TDP) and a new automated Human-Machine Interface system, the facility maintained consistent operations and produced high-quality recovered materials.

The week’s activity led to the recycling of an estimated 9,375 scrap tyres, processing a total of 150,000 pounds (approximately 68,038 kg) of rubber feedstock. From this, approximately 60,000 pounds (approximately 27,215 kg) of recovered carbon black and 75,000 pounds (approximately 34,019 kg) of tyre-derived oil were generated, alongside syngas used to power the process itself.

As a Canadian leader in tyre recycling technology, Ecolomondo views these results as a strong validation of the scalability and reliability of its proprietary TDP system, underscoring the ongoing ramp-up at its Hawkesbury TDP facility. This consistent performance enhances the company's position in the circular economy, turning a challenging waste stream into valuable industrial commodities and demonstrating the commercial viability of its innovative approach.

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The Association of Natural Rubber Producing Countries (ANRPC) has released its Monthly NR Statistical Report for December 2025, providing an overview of key developments in the global natural rubber sector.

As per the report, the natural rubber market is positioned in a strategic accumulation phase that belies superficial price indicators. A critical analysis reveals that while US Dollar-denominated prices showed a slight pullback, this was overwhelmingly due to the appreciation of the Thai Baht rather than a decline in intrinsic value. In Thailand, a key producing nation, local currency (THB) prices remained fundamentally firm, underscoring a resilient domestic price floor that continues to support the long-term upward trend.

This underlying market strength is concretely evidenced by price movements in Malaysia. During the reported period of consolidation, Malaysian SMR-20 prices increased by 2.08 percent and latex prices rose by 2.35 percent. These gains in a major producing hub directly contradict a bearish narrative and confirm that underlying global demand continues to outpace available supply. The current market behaviour is therefore characterized as a ‘cumulation pullback’, a necessary corrective foundation following earlier strong gains, designed to build liquidity before the next advance.

Fundamental data supports this outlook. Global natural rubber production for 2025 is anticipated to grow by a modest 1.4 percent. Although the latest demand figures show a marginal adjustment of -0.7 percent, overall market sentiment remains resilient, bolstered by clear recovery signals from the tyre industry. Critically, the market is now entering the seasonally tight ‘wintering’ period from February to May, when latex production naturally declines. The consolidation and strategic accumulation observed in December 2025 have thus established a solid platform. With supply set to contract and demand holding firm, all conditions are aligned for a sustained price rally as the market moves into early 2026.

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