Elastomer tackifiers are those that produce green tack in elastomers. The term “tack” refers to the ability of two uncured rubber materials to resist separation after bringing them into contact for a short time under relatively high pressure. Building tack of rubber components is an important pre-requisite to enable tyre building on the tyre building drum where different rubber layers are put together on the tyre building drum before they are cured. Another important property of tackifier is, it should retain its tack on storage. A good tackifier, therefore, should have the following properties :

• Very high initial and extreme long-term tackiness
• No adverse effect on the rubber compound cure on scorch
• No interference on (a) rubber to metal bonding (b) rubber to fabric bonding
• Physical properties of the cured rubber remain unchanged
• No effect on the performance of aged rubber compound properties
• Improves rubber compound process reliability
• Show extreme good performance in silica / s-SBR based rubber compound.

In general, NR has enough tack because of the presence of a very high quantity of low molecular weight fraction, having its wide molecular weight distribution. Its low molecular weight fraction also generates during its break down in machines. On the contrary, synthetic rubber lack in tack property because of the absence of enough low molecular weight fraction in them, having narrow molecular weight distribute on (Fig.1). Synthetic rubber also resists in the molecular break down upon mastication and therefore, cannot produce low molecular weight fraction. Resins are typically produced with molecular weights (Mw) between 1,000 and 2,000 with maximum Mw around 3000. The molecular weight is important since tackifying resins work at the surface of the rubber compound and must be able to migrate to the surface to be effective. If the molecular weight is too low, the resin will remain soluble in the elastomer and not migrate its way to the surface. If the molecular weight is too high, the elastomer will be insoluble in the elastomer. Rubber industries use both synthetic and natural resins for tack. Following three types are in major use in the industry :

1. Aromatic Resins (Phenolic, Cumaron Indane)
2. Petroleum based resins
3. Plant Resins ( wood rosin resins,Terpene resins)

Only plant resin is a source of natural resins. However, due to product consistency and different compatibility factors, synthetic resins are in major use. Besides tyre and other rubber applications, the major end-uses for resins are in pressure-sensitive adhesives, hot-melt adhesives, road markings, paints, caulks, and sealants. Manufacturers use hydrocarbon resins to produce hot melt adhesives (for infant and feminine) and packaging applications in addition to glue sticks, tapes, labels and other adhesive applications. All resins are sticky and because of their low molecular weight they migrate (diffuse) easily on the rubber product surface and behaves sticky and that causes tack. Tack property is apparently due to two major reasons :

• Spontaneous diffusion of molecules between two uncured rubber layers.
• Strong molecular forces resulting high degree of crystallinity

Highest level of tack in NR could be due to both the reasons, which means, NR has a high degree of crystallinity (stress induced crystallization) and it has also broad (wider) molecular weight distribution (Fig.1), so that, having plenty of lower molecular fraction can diffuse faster between two layers in contact each other. NR is reported to improve upon its tack on mastication because it generates a higher number of lower molecular weight fraction chains upon breaking down on shearing forces in machines. CR (Neoprene Rubber) shows exceptional adhesive property because it shows the highest degree of crystallinity, even much greater than NR, due to its strong intermolecular attractive force.

Honestly, NR may not require any tackifier because it has enough low molecular weight fraction of chain molecules, due to its wider molecular weight distribution (Fig.1), to be migrated on the rubber component surface and can produce enough tack. It loses its tack mostly because it might have been processed at a higher temperature and is already in the premature vulcanization stage. It can also happen due to the fact that although calendaring or extrusions were done at the right temperature stock was made before adequate cooling and thereby allowed scorching in windup liners. It also loses its tack at cold ambient temperature, in the rainy season and also if the filler level is too high or if the viscosity of the stock is substantially higher than required. However, all synthetic rubber or when synthetic rubber (SBR,BR) is blended with NR, may require to add adequate resins for compound processing.

Except C4,C5 petroleum-based resins, all other types of resins are compatible with NR and is added 1-2 phr. Comparatively C9 petroleum-based resin is better in NR.  Plant-based resins are found to work better in 100% NR. When NR is compounded with synthetic rubber, the tackifier is a must and the dose could be as high as 2-4 phr depending on the content of synthetic rubber, oil and filler in the compound matrix.  All synthetic rubber lag in rubber tack because, in general, synthetic rubber has :

• Narrow molecular weight distribution
• It resisting break down of molecular chains under mechanical shear
• Synthetic rubber is in very pure form

Aromatic Resins (Phenolic, Cumaron Indane) work better in SBR and BR than plant based resins. For hydrocarbon type of elastomers like butyl , halobutyl , EPM and EPDM , petroleum base resin (C4,C5) work better and usually added with 1-2 phr in the formulation, However, with a higher dose of filler, 2-4 phr tackifier could also be added.

Tackifier resins are added to base polymers/elastomers not only  to improve tack (ability to stick) but it also helps in better wetting with filler. Increase in tensile strength by adding resins has been witnessed in different types of elastomers, aromatic resins have been witnessed to increase tensile strength of SBR and its blend.

Effect of Environment on Rubber Tack

The tack of a rubber article is greatly affected by environmental conditions such

as temperature, ozone level and humidity. Environment can not influence tack, however,  if processed rubber compound is used with in 24 hrs. High temperature and humidity conditions have a detrimental effect on the initial tack and tack retention of an elastomer. Phenolic tackifying resins can help improve tack under these conditions, but they have their limits under extreme conditions. Superior tack retention under the influence of high humidity can be often be achieved with epoxy resin modified alkylphenol-formaldehyde polymers.

Hydrocarbon based tackifying resins are sometimes used as a low-cost alternative to phenolic tackifying resins. However, hydrocarbon resins are not as effective at maintaining tack under adverse environmental conditions, like elevated temperature and high humidity, nor do they have the same tack retention. Hydrocarbon resins however, preferred in butyl and EPDM rubber compound due to their compatibility.

Hydrocarbon resins are not as efficient as phenolic tackifying resins, and higher levels are often required to achieve the same tack. High tackifier resin levels can cause a loss in tensile strength, tear strength and, most importantly, hysteresis. In applications where these properties, especially hysteresis, are important, phenolic tackifying resins are excellent choices and should be used.

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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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