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

According to the report, a number of reasons, including limited supply and rising demand, contributed to the volatile pattern in natural rubber prices this month. Consumption was increased by seasonal considerations, especially in China, where stronger demand was evidenced by inventory reductions at key ports. However, tapping efforts were restricted due to manpower shortages and rains in producing regions, which tightened supplies.

Global natural rubber (NR) output is expected to increase slightly by 0.5 percent in 2025 compared to 2024, according to recent data from ANRPC member countries. At the same time, a 1.3 percent increase in demand for natural rubber is anticipated in 2025. As buying demand increased, the market sentiment got more positive, especially when the customary peak season for natural rubber, notably for heavy-duty vehicles and all-steel tyres, began.

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Tokai Carbon Co., Ltd. has finalised the strategic acquisition of Bridgestone Carbon Black (Thailand) Co., Ltd. from Bridgestone Corporation and Asahi Carbon Co., Ltd. The transaction, valued at roughly THB 2.05 billion (USD 56 million approximately), was officially completed on 30 September 2025. This move represents a significant expansion of Tokai Carbon's carbon black operations within the key Southeast Asian market.

Subsequent to the deal's closure, the newly acquired entity has been rebranded as Thai Tokai Carbon Product Rojana Co., Ltd. The company's ownership is now held by Thai Tokai Carbon Product Co., Ltd. at 99 percent and Tokai Carbon Co., Ltd. at one percent, making it a consolidated subsidiary. Tokai Carbon has appointed its Executive Officer, Tatsuhiko Yamazaki, as the new Managing Director to lead the organisation.

This acquisition is a calculated step in Tokai Carbon's wider plan to bolster its global presence and reinforce its production and supply chain capabilities. The company anticipates that this will solidify its standing in the international carbon black sector, which serves the tyre, rubber and various industrial markets. While the specific financial effect on its 2025 results is still being assessed, the move is a clear part of its ongoing growth strategy across Asia.

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Hana Technologies Inc., a manufacturer of radio-frequency identification inlays, has joined the board of Auburn University’s RFID Lab, marking its deeper engagement in setting industry standards for the technology.

The appointment positions the California-based company, which holds ARC Quality certification, alongside other industry participants in shaping research and standards development at the Alabama-based laboratory, which is recognised as a leading academic centre for RFID testing and certification.

RFID technology uses electromagnetic fields to identify and track tags attached to objects automatically and has seen growing adoption in the retail, logistics, and manufacturing sectors for inventory management and supply chain tracking.

“I am excited and honoured to once again collaborate with the Auburn RFID Lab Board, representing Hana RFID,” said Jeremy Liu, chief technology officer of Hana RFID. “This opportunity allows us to contribute to the future of RFID by ensuring quality remains a top priority. Hana is proud of its strong position in the RFID world, and we are committed to supporting our partners with the finest, smartest products available. Together, we will keep moving the industry forward.”

John Erdmann, president and chief executive of Hana RFID, said: “The Auburn RFID Lab has been a key contributor since the very beginning, helping to create a strong and trustworthy RFID ecosystem. We are grateful for this foundation and see our board membership as a chance to give back to the community. Hana will be a fully engaged member – providing continuous feedback, and sharing our knowledge to ensure RFID adoption continues to grow on a solid, reliable base.”

The company, which operates manufacturing facilities globally, did not disclose the term of the board appointment or specific initiatives it plans to pursue in the role.

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Kuraray Co., Ltd. has announced a significant step in its renewable energy transition through a 10-year virtual power purchase agreement (VPPA) between Kuraray Holdings U.S.A., Inc. and Tokyo Gas America Ltd. (a subsidiary of TOKYO GAS CO., LTD.). This agreement, which commences in October 2025, involves the procurement of renewable energy from a solar power project located in Wharton County, Texas.

Annually, the arrangement will supply Kuraray with renewable energy certificates equivalent to 300 gigawatt-hours of electricity. The company projects this initiative will yield a substantial reduction in its greenhouse gas emissions, cutting the Kuraray Group's US emissions by nearly 70 percent. Furthermore, this shift is expected to lower the entire Group's global electricity-related emissions by approximately 40 percent.

This VPPA is a core component of Kuraray's broader environmental strategy, which identifies climate action as a critical priority. The Group has established a long-term objective of achieving carbon neutrality for its Scope 1 and Scope 2 emissions by 2050. To ensure meaningful near-term progress, a new interim target has been set to reduce these emissions by 63 percent by 2035, using 2021 as the baseline year.

Beyond securing external renewable power, Kuraray is implementing a multi-faceted approach to decarbonisation. This includes enhancing energy conservation and operational efficiency across its production facilities, transitioning in-house power generation to natural gas and developing carbon capture, utilisation and storage technologies. The company will also collaborate with its supply chain to encourage a broader shift towards cleaner utility fuels. For advisory services related to this specific VPPA, Kuraray engaged Kinect Energy, Inc., a subsidiary of World Kinect Corporation.

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