Recently, models on the fate of tyre wear particles (TWPs) have estimated that 18% of TWP emissions are transported from roads to freshwater bodies and approximately 2% are led out to estuaries and then marine habitats. What then happens to the remaining 16% of TWP emissions left in the freshwater compartment is not yet clear

The presence of tyre wear particles (TWP) in the aquatic environment is considered an emerging contaminant, and one that has gained increasing interest during the past few years. Although the presence of TWPs in the environment is given greater attention these days, TWPs have probably been present since the dawn of the pneumatic car tyre production in the late 19th century. The first scientific report of tyre dust identification along a roadside was published in 1961. Different perspectives have since been applied to this field of research and almost decade by decade shifted foci from degradation patterns to heavy metal release, to impacts of scrap tyres on the aquatic environment and leaching of chemicals from tyres. More recently, research within this field has been directed towards repurposing scenarios using crumb rubber in turf fields and playground material. Finally, in the 2010s, micronised tyre rubber has become grouped with other polymer debris and hence become part of the polymer landscape usually referred to as ‘microplastics.’ TWPs are considered to represent the majority of microplastics (or polymer debris) in the environment, and the newest calculation on the wear of tyres is estimated at 0.81 kg per person per year.

Now, looking at TWPs through the lens of microplastic pollution, research and information from the microplastics field are very well applicable to TWPs in many instances. With this new perspective of TWPs, increasing awareness of possible adverse effects in the environment follows - how do TWPs distribute in the different environmental compartments (soil, air, sediment, water and biota (living organisms)) and how do TWPs behave when exposed to different abiotic factors in these environmental compartments. For example, UV-radiation or pH, temperature and salinity differences could affect TWPs, but to what degree? A recent paper on this very subject concluded that particularly temperature and mechanical stress could influence the toxicity of TWPs. The focus of tyre production and function have seemingly always been directed towards maximising the three hallmarks: grip, wear and rolling resistance, and rightfully so, but somewhere along the road we forgot to consider where tyre abrasion actually disappears to. Luckily, some scientists already thought of this and today we can begin to lay the foundation to our collected TWP knowledge, based on the available scientific literature.

From roads to water

Research shows that the minority of TWPs end up in the airborne fraction (0.1-10%) and recently TRWPs have been assessed to contribute a low risk to human health in the particulate matter (PM) PM2.5 and PM10 range. So, where to find the remaining 90.0-99.9% of tyre debris emissions? Early research on particulate distribution showed a decreasing concentration of TWPs with increasing distance from the road. From there, TWPs are expected to wash off during rainfalls, transporting them to different environmental compartments. Recently, models on the fate of TWPs have estimated that 18% of TWP emissions are transported from roads to freshwater bodies and approximately 2% are led out to estuaries and then marine habitats. What then happens to the remaining 16% of TWP emissions left in the freshwater compartment is not yet clear and more research is needed to answer this question.

Aquatic organisms living in the water column or the sediment can interact with TWPs in their natural habitats during this particle transportation through freshwater to the marine environment. Although there are no scientific references on field observations of TWP ingestion by aquatic biota yet, few recent observations of this behaviour under controlled laboratory settings have been reported. In 2009 the first observation of the water flea, Daphnia magna, ingesting TWPs was described in the scientific literature and only two years ago the first photos were published showing ingestion of TWPs in the benthic amphipod Gammarus pulex following sediment exposure. Shortly thereafter photos of TWP ingestion in the amphipod Hyalella azteca and opossum shrimps from the mysidae family followed after water-only exposures, and most recently freshwater and marine fish species have been documented ingesting TWPs under laboratory conditions.

The recent focus on particulate effects of TWPs on biota is still in its infancy and the latest development in this field investigates the possible effects of both the particulate fraction and the leachate fraction. The leachate fraction is the suite of chemicals that leach out from TWPs to the surrounding water. Previously, tyre toxicity investigations in the aquatic environment revolved solely around the leachate fraction, which has been the primary focus over the last 30 years. Among the first papers the effect of whole tyre leachate was investigated showing worn tyre leachate to exhibit greater toxicity than leachate from a pristine tyre to rainbow trout. Furthermore, decreasing toxicity was observed with increasing salinity indicating that salinity either influences the leachability of toxic constituents or that an interaction of salts and toxic chemicals is present. Exposure of shredded tyre chips to different bacteria likewise showed a correlation between decreasing toxicity and increasing salinity, concluding that tyre leachate is likely to be a greater threat to freshwater habitats than to estuarine or marine habitats.

Toxicity pattern

Further testing of TWPs and leachate on a freshwater species recently showed a dissimilar toxicity pattern when comparing acute toxicity responses of TWPs or leachate. Here, the amphipod H. azteca was exposed to either TWPs in freshwater or the leachate fraction alone, i.e. with no particulates present. This showed that leachate was more toxic in lower concentrations, presumably because dissolved chemicals are more bioavailable. Although, at higher concentrations, the particle fraction of TWPs became more toxic. This phenomenon very well describes the complexity and discrepancies when working with TWPs in the aquatic environment. It is not just a question of determining toxicity of a single chemical under controlled settings, but rather investigating a mixture of many chemicals in changing ambient environments. This complex matrix of polymer and chemicals can be more or less bound to the particle, which in itself might have adverse effects. However, the particle could also function as a vessel, containing chemicals and making them more or less bioavailable depending on the surrounding environment. Discovering exactly which chemicals leach out under different exposure scenarios, and most importantly, what of that is actually bioavailable to aquatic living species is the more interesting question to answer.

Due to the amorphous nature of rubber, end-of-life tyres (ELTs) have been used as leachate collection material and been used to collect polycyclic aromatic hydrocarbons (PAHs) and metals from contaminated waters. This discrepancy between the different TWP uses that in some cases could deem toxic and have adverse effects but at the same time might serve to mitigate other environmental issues is a great conflict of contradictory traits. Now, we need to unravel exactly when these contradictory traits are possibly affecting aquatic environments negatively and when these traits might be used for our advantage.

So how do scientists quantify TWPs and chemical constituents or ‘biomarkers’ from TWP leachate in water? The quick answer is that no tried and tested procedure is more right than any other now, we simply do not have conformity or guidelines on how to do this. Especially when looking to find particulates from tyre debris, as this is not usually detected when investigating for other polymer debris e.g. microplastics. Therefore, it is expected that the total amount of microplastics has been underestimated due to the lack of data from TWPs, which make up a large part of the estimated microplastic load worldwide and have not been reported on a regular basis. A multitude of methods have been used to estimate TWP emissions by measuring the concentration of chemicals in samples, with more or less success over the years. The biomarkers that have been used to determine TWP concentration most successfully include quantification of benzothiazoles and zinc. Both chemicals are used as part of the vulcanisation process and are also ubiquitous in nature. They are used for manufacturing of other materials, but specific versions can be attributed mainly to tyre manufacturing and are thus the most reliable compounds to measure.

How this emerging field of tyre ecotoxicology will progress ultimately depends on cooperation between different stakeholders having a common goal to pursue. The one thing that we can probably all agree on, is the need for tyres and other rubber products in our society. How we then fill that need, and what future decisions we make to maximise our understanding of the possible negative implications of TWPs in the aquatic environment is of paramount importance. Our job now is to continue our research within this field and ultimately prevent excess and unnecessary pollution of the water bodies that we all depend on, in a manner that stays true to both the environment and our need for safe and reliable tyres. 

*The author is a PhD student in Environmental Biology at Roskilde University, Department of Natural Science and Environment, Denmark, with funds from Danish Environmental Analysis

References

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Solvay has secured a favourable ruling from the European Patent Office, which upheld the validity of its European patent EP 3 971 138 B1 following a challenge by WE Soda Ltd. The opposition, initiated on 13 February 2025, concluded with a decision on 19 May 2026 that maintains the patent’s protection with only minor amendments. While the ruling is subject to potential appeal, it reinforces Solvay’s position regarding its proprietary industrial processes.

Granted in May 2024, the EP ’138 patent safeguards Solvay’s method for treating and recycling purge streams in the production of sodium carbonate and sodium bicarbonate. The intellectual property extends to the overall manufacturing process that incorporates this recycling technique, as well as the final products derived from it. This patent is part of a broader family that includes EP 2 878 579 B1, which is already the subject of a separate legal dispute between the two companies.

In a related Dutch legal battle, Solvay had initiated infringement proceedings in August 2021 against WE Soda and its affiliates, including Turkish subsidiaries, concerning the EP ’579 patent. The District Court ruled in Solvay’s favour on 3 December 2025, affirming the patent’s validity and issuing an injunction that prohibits the defendants from importing and supplying their products to the Netherlands. WE Soda and the associated entities have since appealed that judgment, with the appeal currently pending.

The recently upheld EP ’138 functions as a unitary patent, which enables Solvay to pursue infringement actions through the Unitary Patent Court in a single, expedited proceeding covering at least eighteen member states. Such actions offer the potential for injunctions to block imports of infringing goods across a wide jurisdiction. Solvay has reiterated its commitment to protecting its innovations and vows to take decisive legal measures globally to enforce its intellectual property rights, viewing such enforcement as fundamental to maintaining fair market competition.

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India’s zinc oxide industry is undergoing a structural shift from volume-driven manufacturing to value-led specialisation and Punia Group’s trajectory reflects both the opportunity and the pressure within this transition. As demand from tyres, EVs and global markets intensifies, the company is expanding its capabilities while navigating volatility in raw materials, regulatory tightening and supply chain disruptions. Its evolution underscores a broader industry reality that growth is no longer defined by scale alone but by consistency, sustainability and the ability to stay competitive in an increasingly complex global ecosystem.

For over four decades, Punia Group of Industries has steadily transformed itself from a modest, commodity-focused manufacturer into a forward-looking player in zinc oxide. The company’s journey reflects not just its own resilience but also the broader evolution of India’s manufacturing ecosystem.

In its early years, the business operated in a market driven largely by volumes and cost competitiveness. However, with a clear understanding that long-term sustainability required differentiation, the organisation began investing in process improvements, quality consistency and customer-centric innovation.

Over time, strategic inflection points such as technology upgrades and introducing efficient systems enabled the company to move up the value chain and strengthen its market position.

Underpinning this evolution has been a strong foundation of ethics, transparency and disciplined governance, which has guided every phase of growth.

“The zinc oxide and rubber chemicals industry itself is undergoing a significant transformation. What was once a commoditised, price-driven sector is now being reshaped by increasing demands for performance and sustainability,” noted Chief Executive Officer Siddharth Punia.

He added, customers, particularly in the tyre and automotive sectors, are seeking materials with consistent quality and lower environmental impact. While commodity segments continue to exist, the competitive advantage today lies in innovation, compliance and the ability to meet evolving global standards.

Against this backdrop, Punia Group is charting its next phase of growth with a clear and structured vision for the next three to five years.

THE NEXT PHASE

The company is focusing on expanding production capacity in a calibrated manner, ensuring that every addition is backed by robust demand visibility and operational readiness. A key area of alignment is with the growing demand from electric vehicles, advanced tyre technologies and industrial applications that require precision-engineered materials.

The organisation’s approach remains firmly rooted in systematic growth prioritising sustainability, efficiency and long-term value creation over short-term scale. This is evident by the company obtaining IATF 16949 and REACH certifications.

“The global business environment has become increasingly complex in recent years. Supply chain disruptions triggered by the Covid-19 pandemic followed by ongoing geo-political tensions such as those in the Middle East have had a direct impact on raw material sourcing and pricing,” contended Punia.

He added that zinc, being a globally traded commodity, has experienced considerable volatility, affecting cost structures across the industry. In response, companies are rethinking their supply chain strategies by diversifying sourcing, building strategic inventories and reducing overdependence on specific geographies.

Punia Group has taken pro-active steps in this direction by strengthening supplier relationships and exploring regional procurement options, ensuring continuity while adhering to its principles of fair and responsible sourcing.

TICKING THE CONS

Operating in this environment also brings a unique set of challenges. “Raw material price fluctuations, stringent environmental regulations and demand uncertainty linked to global economic cycles remain key concerns,” said Punia.

The company’s response has been grounded in discipline and foresight, investing in energy-efficient and environmentally compliant technologies, driving process innovation to reduce waste and maintaining agile production systems.

“Importantly, these efforts are guided by a strong ethical framework that emphasises compliance, environmental stewardship and accountability to all stakeholders including customers, employees and the communities we operate in,” he noted.

GRABBING THE OPPORTUNITIES

At a macro level, India’s emergence as a strategic manufacturing and consumption hub offers significant opportunities for the zinc oxide and rubber chemicals industry. The country benefits from competitive cost structures, a rapidly expanding domestic market driven by automotive and infrastructure growth and supportive government initiatives aimed at boosting manufacturing and exports.

Additionally, global supply chain re-alignments are creating opportunities for India to position itself as a reliable alternative to traditional manufacturing bases, further strengthening its role in the global value chain, informed Punia.

Reflecting on its 40-year journey, Punia underscores the importance of adaptability, cost discipline and principled decision-making. He stated, “Building a manufacturing-led business in a cyclical industry requires not just operational excellence but also consistency in values and vision.”

The company’s emphasis on systematic, step-by-step growth has enabled it to navigate multiple economic cycles while maintaining financial and operational stability. Past disruptions, whether economic downturns or supply shocks, have reinforced the importance of resilience, diversification and long-term planning.

CATERING TO DEMANDS

The company recently commissioned its new Tirupati plant that will be a modern, environmentally focused facility using the widely adopted French process to manufacture zinc oxide.

This involves vaporising zinc metal, reacting it with oxygen to form zinc oxide, then cooling, filtering, testing and packaging the final product. The plant will produce multiple grades tailored to customer requirements.

“Raw materials will largely come from zinc dross sourced locally and globally from the galvanising industry. The process is designed as a closed-loop, zero-waste system, where by-products are re-used,” he said.

“Over the past decades, technology has continually evolved and we have consistently stayed ahead of the curve, adopting innovations well before they became industry standard. We introduced efficient collection systems that are not only environmentally responsible but also enhance product quality while prioritising worker safety,” informed Punia.

He contended that the plants’ re-designed furnaces enable cleaner, more efficient combustion, reducing emissions and delivering meaningful energy savings. Automation has been integrated wherever feasible to improve consistency and operational efficiency, while the health and safety of the workforce remain central to every decision that the company makes.

“Beyond operations, we are equally committed to giving back to the community. We actively support nearby villages through healthcare initiatives, encourage and sponsor sports activities and contribute to local infrastructure development, reinforcing our role as a responsible and engaged stakeholder,” he said.

Sustainability efforts like reducing fuel consumption through heat recovery and furnace optimisation has already achieved 15–20 percent savings. The company is also enroute to install heat recuperators and planning a transition to solar energy to meet most electricity needs.The facility also set internal benchmarks for efficiency and sustainability, particularly through improved energy utilisation and process optimisation.

During the Covid period in 2020, the company expanded this plant significantly, reinforcing its role as a high-output, strategically important unit. In addition to serving domestic demand, the Gujarat location offers strong logistical advantages for exports, especially through proximity to western ports like Mundra, enabling access to global markets.

“Even as the Tirupati plant strengthens southern reach, the Gujarat facility continues to anchor the company’s western and export-oriented operations, making the two plants complementary in terms of geography and market coverage,” said Punia.

FUTURE OUTLOOK

Looking ahead, the alignment between industry and government policy will play a crucial role in sustaining growth momentum. While India has made notable progress in supporting the speciality chemicals sector, further reforms in areas such as regulatory simplification, faster environmental clearances and infrastructure development can significantly enhance ease of doing business and global competitiveness.

As the industry continues its transition from commoditisation to specialisation, companies that combine innovation with integrity will define the future. With its strong ethical foundation, commitment to systematic growth and forward-looking strategy, Punia Group of Industries is well-positioned to capture emerging opportunities while contributing meaningfully to India’s evolving industrial landscape.

Punia Group’s growth narrative is compelling, but sustaining momentum will depend on execution amid volatility and rising expectations. As the industry shifts towards specialisation, the real test lies in balancing cost pressures with innovation and sustainability, ensuring that expansion translates not just into scale but into durable competitive advantage.

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As modern automobiles evolve, especially electric vehicles, noise reduction has become essential across all segments, not just luxury models. With electric powertrains eliminating engine noise, road and tyre acoustics are now central to vehicle refinement. Henkel plays a key role in this shift, leveraging its materials science and adhesive technologies in automotive manufacturing. The company is now focused on transforming the increasingly important field of tyre acoustics through advances in chemistry, process engineering and strategy.

Dr Rainer Schönfeld, Head of Global Market Strategy for Henkel’s Automotive Components business, leads this initiative. He explains how the concept of placing foam inside a tyre has become a strategic technology in the electrification era, and how Henkel aims to redefine the process.

For over a decade, ‘silent tyres’ have featured in premium vehicles. These tyres use polyurethane foam inside the cavity to dampen resonance generated as the tyre rolls, often likened to a drum sound. As the tyre rotates, a standing wave forms within the cavity, typically between 200 and 250 hertz, and this energy travels through the chassis into the cabin, making it audible.

“In the early years, it was a very small business. For nearly eight years, there was limited traction. Over the last five years, however, we have seen significant growth,” Dr Schönfeld says.

The shift is closely tied to electric vehicles. Without the masking effect of an internal combustion engine, road noise becomes far more prominent, particularly at lower speeds. Foam-based solutions, Dr Schönfeld argues, address a problem that cannot be solved by tyre compounds alone.

“You can influence noise through the compound, but you will never reach the same level of effect as with foam. The cavity noise will always exist,” he says,

Laboratory tests show reductions of roughly 10 to 20 decibels at the critical frequency – enough to produce a noticeable improvement in cabin refinement.

However, the current manufacturing model for these tyres is inefficient. Foam is produced in blocks, cut to various sizes and shipped to tyre plants, where it is bonded inside the tyre with adhesives. While effective, this method adds significant complexity.

Manufacturers must manage dozens of foam variants across tyre sizes. Warehousing requirements expand, as foam – largely air – occupies significant volume. Internal logistics become cumbersome, with material repeatedly moved between storage and production lines. The cutting process generates waste, while bonding introduces additional quality control challenges.

“You are dealing with up to 10 or 20 different foam dimensions. And you are essentially storing and transporting air. That creates both cost and complexity,” Schönfeld notes.

It is this structural inefficiency that prompted Henkel to rethink the process from first principles. The result is its patented LOCTITE LASER-FIT process, a system that replaces pre-formed foam and adhesives with a fully integrated, three-step approach: cleaning the tyre, applying a liquid foam precursor and activating the structure through laser processing.

At its core, the innovation lies in applying a reactive liquid formulation directly into the tyre. The material expands and cures at ambient temperature, forming an acoustic foam in the place. The approach eliminates pre-cut foam patches, manual handling and the adhesive bonding stage altogether.

“The idea itself is quite obvious. But making it work reliably in a production environment is highly complex,” Dr Schönfeld says.

One of the central technical challenges relates to the nature of polyurethane foam. When it forms, it naturally develops a surface skin. While necessary during expansion, this skin reduces the acoustic effectiveness and the mechanical durability of the foam. Henkel’s process addresses this through an integrated laser step, developed with specialised partner 4Jet Laser System, which removes the surface layer and exposes the open-cell structure beneath.

Dr Schönfeld explains, “The acoustic performance depends on having an open-cell surface. The sound energy must be able to enter the foam and be dissipated.”

The process is both rapid and precise. The liquid precursor is applied within seconds, begins expanding almost immediately and completes foaming within roughly 30 seconds, with full curing achieved shortly thereafter. The tyre is rotated during application, using centrifugal force to distribute the material evenly and prevent sagging.

What distinguishes the system is not only its chemistry but also its adaptability. The application pattern can be adjusted dynamically for different tyre sizes and geometries without the need for retooling. This removes one of the most persistent constraints of the traditional model, where each tyre dimension requires a specific foam insert.

The implications extend well beyond process simplification. By eliminating pre-formed foam, manufacturers reduce material waste entirely. Storage requirements shrink, as liquid precursors occupy a fraction of the space required for foam blocks. Logistics become more efficient, while automation ensures consistent application quality.

“The whole system becomes simpler. You remove complexity, reduce waste and improve consistency at the same time,” Dr Schönfeld says.

As with any automotive innovation, however, trade-offs must be managed carefully. The addition of foam increases tyre weight by approximately 300 to 400 grammes – modest but not insignificant in a sector where efficiency gains are often incremental.

Thermal behaviour presents another consideration. Foam inherently provides some insulation, raising the risk of heat build-up under high-speed conditions. Dr Schönfeld emphasises that mitigating this effect was a central development requirement. “You have to ensure that the foam does not lead to critical temperature increases. The integrity of the tyre must never be compromised,” Dr Schönfeld adds.

Durability is equally demanding. The foam must withstand sustained mechanical stress over tens of thousands of kilometres without cracking or degrading. Early-stage materials exhibited such weaknesses, requiring significant refinement to achieve the necessary fatigue resistance.

The technology must also coexist with other evolving features of modern tyres. Sensors for monitoring pressure and temperature are increasingly standard, and integrating these components within foam-based systems remains an area of ongoing development. Similarly, compatibility with puncture sealants is being evaluated, although the foam itself – being open-cell – does not provide sealing capability.

From a market perspective, silent tyre technology has followed a familiar trajectory, beginning in luxury vehicles before gradually moving into premium and mid-range segments. Electric vehicles have accelerated this transition, as the absence of engine noise heightens the importance of road noise mitigation.

“In electric vehicles, the application rate is much higher. But we also see it moving into other segments over time,” Dr Schönfeld notes.

Adoption remains concentrated in original equipment markets, with limited penetration in the aftermarket. While replacement silent tyres are available, widespread retrofitting is constrained by economics, scale and regulatory requirements.

Geographically, interest is broadly distributed. Dr Schönfeld points to engagement from tyre manufacturers across Europe, North America and Asia, with India emerging as a market of growing relevance. Road surface conditions, climatic factors and rapid infrastructure expansion create distinct acoustic challenges that may favour such solutions.

Perhaps the most consequential dimension of Henkel’s approach lies in sustainability. Conventional silent tyre designs face a critical limitation: recyclability. Certain adhesives used in bonding processes can interfere with tyre shredding, causing operational issues such as equipment clogging and even fire hazards. As a result, some recyclers exclude silent tyres altogether.

By eliminating adhesives from the process, Henkel’s system enables tyres to be processed through standard recycling streams. “Recyclability is becoming increasingly important. Our solution avoids the issues that exist with some traditional bonding systems,” Dr Schönfeld says.

This aligns with emerging regulatory frameworks, particularly in Europe, where stricter requirements around end-of-life tyre management are expected. Concepts such as digital product passports – capturing data on materials, usage and recyclability – are likely to become standard.

Henkel’s LOCTITE LASER-FIT process is currently undergoing validation with tyre manufacturers, with commercial deployment expected towards the latter part of the decade. “We are still in the optimisation phase. Full validation takes time, but the direction is clear,” Dr Schönfeld says.

In many respects, the evolution of silent tyres reflects a broader shift in automotive engineering. Performance is no longer defined solely by speed or efficiency; it increasingly encompasses refinement, comfort and sensory experience.

“It is about comfort. And comfort is becoming more important as vehicles evolve,” Dr Schönfeld reflects.

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HS HYOSUNG ADVANCED MATERIALS made a significant impact at InLEX KOREA 2026, the international defence exhibition hosted from 9 to 11 June at the Daejeon Convention Center. The company placed its advanced material technologies at the forefront, positioning them as future cornerstones of the defence industry.

The exhibition, organised by the Ministry of National Defense and the Army Headquarters, gathered military and civilian stakeholders to chart the sector’s trajectory. HS HYOSUNG ADVANCED MATERIALS used the platform to unveil defence applications of its proprietary carbon fibre, aramid and lyocell while actively building customer networks and hunting for global defence contracts.

Three specialised units collaborated on the ground. The Carbon Materials PU featured aerospace-grade propulsion tanks for drones and satellites alongside chopped fibre and 3K carbon fabrics. Concurrently, the Aramid PU presented ballistic helmets and body armour woven from heat-resistant, high-strength aramid yarns aimed at maximising soldier safety.

In a separate showcase, the Tire Reinforcement Materials PU introduced eco-friendly lyocell yarn and carbonised lyocell fabrics. The Aramid PU’s protective gear and the Carbon Materials PU’s lightweight composites collectively demonstrated how HS HYOSUNG ADVANCED MATERIALS is broadening the use of advanced composites in military applications.

Lim Jin Dal, Chief Executive Officer of HS HYOSUNG ADVANCED MATERIALS, said, “Through this exhibition, we hope to demonstrate how our advanced high-performance materials technologies can be applied to Korea’s defence industry. Building on our continuous R&D efforts and commitment to localising advanced materials, we will contribute to establishing a stable supply chain and continue growing together with the defence industry.”

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