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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In a significant expansion of their existing recycling partnership, Alcoa Australia and Tyrecycle have commenced a new programme to repurpose used conveyor belts from Alcoa’s mining operations. The first reel of used belt was successfully delivered to Tyrecycle’s East Rockingham processing plant, marking a pivotal step in addressing a major waste stream. This initiative builds upon the companies' established contract for recycling off-the-road tyres and forms a core component of Alcoa’s broader corporate strategy to minimise, recycle and reuse waste generated by its Western Australian activities.

The ambitious programme will see approximately 32 kilometres of used conveyor belt transported to the facility over several months. In its initial phase, the collaboration aims to recycle 80 reels of belting. Tyrecycle will process an estimated 100 tonnes of this material weekly, transforming it into rubber crumb. This output will supplement the more than 300 tonnes of Alcoa’s used tyres the company already recycles annually. The primary focus of the recycling process is to reclaim the steel wire embedded within the belts and to convert the rubber into a versatile crumb product.

This crumb is destined for a wide array of practical applications, serving as a valuable additive in road construction bitumen, and as a raw material for creating surfaces for sports fields and playgrounds, adhesives and various moulded rubber goods. Tyrecycle emphasises a circular economy vision, aiming not just for repurposing but for eventually integrating recycled material back into the manufacturing of new conveyor belts. Since its inauguration, the East Rockingham facility has been instrumental in providing Western Australian mining operators with solutions to decarbonise their supply chains. This partnership with Alcoa simultaneously supports regional employment and advances shared environmental goals by diverting substantial rubber waste from landfill and giving it a productive new life.

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KRAIBURG TPE has introduced a new series of thermoplastic elastomers engineered specifically for e-bike handles. This THERMOLAST R RC/UV/AP series is designed to merge sustainability with high performance and improved ergonomics. A central feature of this material is its composition, which incorporates between 15 percent and 40 percent recycled content, directly addressing the industry's push towards more eco-conscious manufacturing.

The compound provides a soft-touch grip for enhanced rider comfort and control, alongside resistance to chemicals and ultraviolet light. Its lightweight nature contributes significantly to the overall reduction of e-bike weight, with some modern models now being up to 50 percent lighter than traditional designs. From a production standpoint, the material is formulated for multi-component injection moulding and bonds reliably to polypropylene, facilitating complex and innovative handlebar designs. Manufacturers can also select from a wide hardness range to customise the grip feel without sacrificing the material’s inherent durability or safety.

The performance of this TPE series is validated by extensive testing, including a two-year outdoor exposure that confirmed its resilience against harsh weather. It also maintains stability in temperatures up to 90°C, ensuring reliable long-term use. This product launch is part of KRAIBURG TPE's broader sustainability commitment, which includes developing bio-based TPEs, holding certifications for recycled content and providing Product Carbon Footprint data. The company's efforts have been recognised with an EcoVadis Gold Medal, and it has reaffirmed its commitment to Science Based Targets initiative (SBTi). This new material series positions KRAIBURG TPE as a pivotal partner in creating greener and more functional e-bike designs for a rapidly growing market.

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Bekaert's Ultra & Mega Tensile steel cord solutions have received the prestigious 2025 China Green Point Award for their significant role in advancing the tyre industry's shift towards low-carbon manufacturing.

This innovative reinforcement technology utilises high-strength steel, which allows for the production of lighter and more durable tyres while using less raw material. A key environmental benefit is the substantial reduction in rolling resistance, which directly improves vehicle fuel efficiency and leads to lower CO₂ emissions. Furthermore, the technology supports circular economy principles by incorporating steel with a high recycled content.

With over seven decades of expertise, Bekaert empowers leading global tyre manufacturers to create high-performance, sustainable tyres, thereby accelerating the transition to greener mobility on a large scale.

The company shared the achievement in a social media post: “A big thank you to our teams for their leadership in driving this achievement, and to our partners across the industry for making sustainable mobility a reality. This award is more than recognition: it’s proof of how materials innovation, powered by people, can accelerate change from the ground up – literally.”

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Ecolomondo Corporation, a Canadian developer of sustainable technology for recycling scrap tyres, is reporting significant commercial progress at its Hawkesbury TDP facility. The company is experiencing a substantial rise in demand for its recycled products, leading to strong sales growth.

A key development involves a major customer who, since mid-July 2025, has purchased 12 truckloads of recovered carbon black (rCB), representing approximately 276 metric tonnes. This client has signalled its intention to increase order volumes further as it transitions its business from another supplier. In another positive step, a second US-based customer has formally approved Ecolomondo's recovered carbon black for use in its manufacturing supply chain and is anticipated to commence bulk orders imminently. Additionally, the company has successfully shipped its 26th tanker of tyre-derived oil, amounting to 520 metric tonnes with an estimated value of USD 416,000.

This upward trend is reflected in the financial results. For the period from 1 January to 31 August 2025, revenues reached USD 640,986, a 91 percent increase compared to the USD 336,078 recorded during the same timeframe in 2024. This growth is largely attributed to the rising sales of recovered carbon black. To support the escalating production needs, Ecolomondo plans to hire and train additional personnel for the Hawkesbury facility. The company notes that, as expected during this operational ramp-up phase, the facility is not yet generating gross margins and continues to operate at a loss.

Jean-François Labbé, Interim CEO, Ecolomondo Corporation, said, “These milestones demonstrate the reliability of our production and the repeated nature of revenues we are building.”

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