Polymer producers have responded to the changing tyre industry expectations, their innovations take into account a more reactive functionality within polymer architecture, and this is closely matched by increasingly greater degrees of filler surface chemistry. As a result, tyre compound properties may now be tailored to meet quite specific tyre performance targets.

Tyre processing methods also underwent progressive stages of modernisation in recent years, for example, more sophisticated reactive mixing technology together with high-speed extrusion systems allowing for direct extrusion onto the building drum become established as cost effective production routes for many of the major producers.

These advancements however bring about their own conflicts, processing pathways involving multiple stages, often with the ability to rework compound or adjust rheological properties by additional time or energy input during the process are no longer viable options for most tyre producers. It has thus become necessary to achieve processability through an increasingly narrow operating window.

Formulations optimised to achieve peak tyre performance in most cases also tend towards more challenging processing characteristics. This is to be expected; the use of high and narrow molecular weight reactive polymers alongside fillers having high surface area and chemistry, often in loadings above that of the polymer are the norm. The trend towards usage of high loading of plasticiser and resinous materials to adjust tyre tread grip and traction response all contribute to a less forgiving processing nature. Often those compounds that are highly reinforced appear the most fragile during processing and poor green strength with an easily tearing or crumbly compound appearance are often-discussed processability issues. By contrast, the use of high loadings of resins and plasticisers, for example in winter or high-performance tyre formulations, results in compounds that during processing can more resemble chewing gum than tyre treads!

The use of process additive chemicals in an attempt to overcome the processing limitations observed gives rise to further conflicts; Lubricant additives might improve compound surface appearance; however, green strength will probably further reduce due to the unwanted softening effect. The same is true for release additives where lower tack unfortunately remains at a higher value than the also lowered tensile strength of the compound. Filler dispersion is often targeted by additives, however higher loading of fillers mandate equally higher additive loadings, we should more accurately discuss loading as “parts per hundred of filler” not rubber, and under the appropriately higher additive loading, the risk of interference with vulcanisation properties or even additive migration leading to surface bloom become realistic concerns.

Conflicting performance characteristics

The development team at Schill + Seilacher has recognised the need to decouple conflicting performance characteristics found within conventional process additive chemistries. As a result, innovation within our Struktol® range offers tyre compounders opportunities to achieve processability without compromise.

Reduced viscosity leading to better extruder flow properties and improved surface appearance, whilst at the same time achieving an increased compound green strength can be realised by use of Struktol HT 300, a new generation of reactive process additive.

An extract of key processing and property influence in a typical highly silica filled sSBR tread compound are highlighted in the following data.

Significantly lowered Mooney viscosity as well as better mixer batch off with reduced sticking to the mixer rotor and gate with Struktol HT 300 are observed.

An increase in compound green strength was obtained by the addition of Struktol HT 300; this is the opposite of expectation for conventional process additive chemistry, where reduced viscosity is obtained. In addition, the filler dispersion as evidenced by a reduction in the so-called “Payne Effect” as tested in uncured compound by means of RPA strain sweep, is also improved.

Lab extrusion trials, using cold feed extruder demonstrate improved surface appearance and lower compound pressure achieved by use of Struktol HT 300, both desirable processing conditions.      

Physical properties are also acceptable, with a progressive increase in tensile strength an elongation and maintenance of stiffness with loading of 6 phr of process additive, only at higher loading of 12 phr would a balancing slight reduction in process oil be required.

Compound hardness remained unchanged alongside improved wear resistance, as measured by DIN abrasion loss testing, even when using higher loading of process additive, are important aspects.

The ability to decouple the relationship between lubrication, important for improved rheological behaviour, and the maintenance of strength and stiffness in both the uncured and vulcanised condition is only possible with such new and innovative class of process additive. This departure from conventional thinking offers the tyre compounder significant degree of freedom to retain the benefits in terms of easier processability without sacrifice of key tyre performance properties.

In this example, the use of Struktol HT 300 prioritised green strength alongside reduced viscosity. By contrast, our new Struktol HT 250 decouples release from other properties, especially effective for winter tyre tread; compound stickiness is resolved without compromise of viscoelasticity.

Ensuring that migration and ultimately bloom within rubber compounds is kept to the lowest level is important for final article aesthetics, for tyres additional considerations arise; they are composite structures, therefore it is imperative that chemicals do not migrate across boundary layers in an uncontrolled manner, which could result in changed behaviour or interfacial adhesion failure over time. In order to limit migration, the compatibility, solubility and concentration of chemicals are carefully considered. However, one method of ensuring long-term stability involves chemically binding the additive within the vulcanisation network.

At Schill + Seilacher, we have achieved this degree of crosslinking capability for a number of new-generation Struktol process additives. Their usage allows the compounder to avoid completely the risk of migration and bloom due to additive presence.

Photographs of two vulcanised rubber sheets based on the same formulation. On the left-hand side, evidence of typical surface bloom, which may occur due to migration of a conventional process additive, on the right, containing reactive additive Struktol HT 600 as replacement, it can be seen that bloom was eliminated.

This technology also opens tremendous opportunities to “fix” process additives in place within the respective component, the role of additives withinthe cross-linking mechanism may additionally lead to vulcanisate performance characteristics.

                                                                                  One interesting tyre related example involves the development of a superior tyre curing bladder performance, here we have developed new reactive plasticisers called Struktol HT 815 and Struktol HT 820, their use is directed towards resin-cured butyl rubber. This combination of polymer and curing system provides for superior heat resistance with excellent flex fatigue resistance and is used as the basis for tyre curing bladders. Here the replacement of widely used castor oil as plasticiser with new Struktol HT 800 series product leads to a significantly improved bladder performance life, with greater stability in viscoelastic properties. Reduced stiffening of the bladder, due to lower degree of plasticiser migration translated into a much lower flex-cracking rate, especially after high temperature steam ageing.

Reactive Struktol plasticisers, HT 815 and HT 820 exhibit a significantly reduced flex cracking rate when compared to the widely used castor oil, which readily migrates from the bladder; as a result, significant extension of bladder service life is possible.

New reactive process additives, with tailored functionality to closely match the specific chemistry of polymers, fillers and cure systems are actively developed. These innovative products under the Struktol brand offer tyre compounders a more comprehensive toolkit in order to tailor compound performance to meet tyre performance demands. The conflicts of property versus processability diminish and new possibilities emerge!

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In a strategic move to secure its supply chain, Aluminium Bahrain B.S.C. (Alba) has entered into a partnership with India's Epsilon Carbon. The two companies have signed a non-binding Memorandum of Understanding to explore a long-term arrangement for the supply of liquid coal tar pitch, a critical raw material for aluminium smelting.

This initiative, launched at the Gateway Gulf Forum 2025 in Bahrain, is designed to enhance Alba’s operational security and efficiency. Concurrently, it supports Epsilon Carbon's strategy to establish a new coal tar pitch melting facility within the Kingdom of Bahrain. The agreement paves the way for future detailed negotiations, which will include trial deliveries and the finalisation of quality and commercial terms.

Ali Al Baqali, CEO, Alba, said, “Our collaboration with Epsilon Carbon marks an important milestone in Alba’s journey to reinforce supply chain reliability and maintain the highest standards of quality. This partnership not only secures a key input for our operations but also supports the growth of Bahrain’s industrial sector. We are confident that this alliance will deliver lasting value for both organisations.”

Vikram Handa, Managing Director, Epsilon Carbon, said, “Our collaboration with Alba is an important step toward sustainable industrial growth. With our coal tar distillation capacity set to reach 750,000 tonnes by 2027 and a USD 20 million investment in the Kingdom of Bahrain, we aim to strengthen regional collaboration and supply chain resilience. This will not only reinforce the India – Kingdom of Bahrain industrial corridor but also help reduce the carbon footprint and realise our vision for a more sustainable and efficient aluminium industry.”

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A major new academic and industry reference, Sustainable Materials for Rubber and Allied Industries, has been released by CRC Press/Taylor & Francis. The 724-page volume brings together science, technology, policy and industrial practice to explore how one of the world’s most essential material sectors is transitioning towards sustainability.

The rubber industry plays a critical role in mobility, healthcare, defence, infrastructure and consumer products. Yet, for decades, most rubber compounds have relied on fossil-based feedstocks and additives. As the world confronts the realities of climate change, resource depletion and waste accumulation, the industry now finds itself at the centre of global discussions on sustainability and circularity.

This book addresses that challenge directly, not as a philosophical concept but as a practical and scientific journey. It examines the material, processing and policy transitions required to build a sustainable future for rubber and tyre manufacturing.

What the Book Contains

Structured across fourteen detailed chapters, the volume covers:

• Foundations of Sustainability and Circularity — explaining environmental, social and economic drivers shaping modern material science.
• Natural Rubber — explored as the industry's most significant renewable resource, along with sustainability challenges in cultivation and processing.
• Bio-Based and Sustainable Synthetic Rubbers — highlighting advances in monomers and green polymer chemistry.
• Sustainable Fillers, Fibres and Reinforcements — including biomass-derived fillers, recycled fibres and improved steel cord systems.
• Curing Systems, Antidegradants, Resins and Processing Aids — re-examined through environmental performance, toxicity and lifecycle impact.
• Thermoplastic Elastomers and Thermoplastic Vulcanisates — offering recyclable and energy-efficient solutions for multiple applications.
• Recycling, Devulcanisation and Circular Economy Models — reviewing the state of the art and emerging industrial-scale technologies.
• Global Regulation and Policy — outlining responsibility frameworks and sustainability compliance trends.

Throughout the book, laboratory research, practical industrial experience, and case-study insights are blended to provide a realistic and applicable reference for scientists, engineers, educators, sustainability strategists, and manufacturing leaders. The work recognises the progress already made by leading manufacturers while setting a scientific and technological roadmap for the years ahead.

The message is clear: sustainability is not merely a direction for the rubber industry — it is its future operating principle.

Short Note About the Authors

The book is authored by five recognised leaders in rubber science and sustainability:

• Professor Anil K. Bhowmick
• A globally respected polymer scientist and Research Professor at the University of Houston, formerly Professor of Eminence at IIT Kharagpur and founder of IIT Patna. He has over 600 research publications, multiple patents, numerous international awards and a distinguished record of advancing rubber science worldwide.
• Dr Rabindra Mukhopadhyay
• Director & Chief Executive of HASETRI and Director (R&D) at JK Tyre. With more than 45 years of industrial leadership, he is known for his contributions to reverse engineering, sustainable materials, circular economy practices and technology development in tyres and elastomers.
• Dr Jagannath Chanda
• Senior Research Scientist at HASETRI, specialising in sustainable composites, failure analysis and structure–property relationships, with significant contributions to academic literature and industrial innovation.
• Dr Barun Kumar Samui
• Principal Scientist at HASETRI with extensive industry experience in reinforcement textiles, composite materials and the performance optimisation of rubber products.
• Dr Riya Koley
• Postdoctoral Fellow at Polytechnique Montréal with research expertise in polymer chemistry, green additives, elastomer processing and nanomaterial-enhanced sustainable rubber systems.

Together, the authors bridge academic excellence, industrial experience and long-term engagement with global sustainability efforts — making this book both authoritative and practical for the future of the rubber and allied industries.

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The global natural rubber (NR) market experienced fluctuating prices in August 2025 as supply constraints coincided with signs of improving demand, the Association of Natural Rubber Producing Countries (ANRPC) said in its latest Monthly NR Statistical Report.

The association noted that seasonal factors supported stronger consumption, particularly in China, where declining port inventories signalled healthier demand. However, heavy rainfall and labour shortages in key producing regions curtailed tapping activities, tightening supply conditions.

“Natural rubber prices experienced a fluctuating trend due to several factors, including constrained supply and improving demand,” ANRPC said. “Seasonal factors boosted consumption, particularly in China, where inventory reductions at major ports indicated improved demand. However, rainfall and labour shortages in producing regions limited tapping activities, tightening supply.”

According to updated data from member countries, global natural rubber production is projected to increase by 0.5 percent in 2025 compared with 2024, while demand is expected to grow by 1.3 percent over the same period.

The association said market sentiment had turned “increasingly optimistic” with stronger purchasing interest, driven by the traditional peak season for natural rubber, especially from the all-steel tyre and heavy-duty truck segments.

The ANRPC encouraged subscribers and stakeholders seeking more in-depth insights to refer to the full report or contact the ANRPC Secretariat for subscription details.

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India has launched an anti-dumping investigation into imports of Halo-Isobutene-Isoprene Rubber (HIIR) from China, Singapore and the United States, following a complaint from Reliance Sibur Elastomers Private Limited, the Directorate General of Trade Remedies (DGTR) said in a notification.

The domestic producer alleged that the three countries were exporting the rubber to India at unfairly low prices, causing injury to the local industry. The company has sought the imposition of anti-dumping duties on the product, which is used in tyre inner liners, hoses, seals, tank linings, conveyor belts and protective clothing.

The DGTR said there was prima facie evidence that imports had risen “significantly” and were being sold below normal value, resulting in price depression and affecting the domestic manufacturer’s capacity utilisation and profitability. The authority noted that the dumping “is causing material injury to the domestic industry”.

The investigation will cover the period from July 2024 to June 2025, with an examination of injury trends dating back to April 2021.

HIIR, also known as halobutyl rubber, is classified under the broader synthetic rubber tariff category. Reliance Sibur Elastomers is currently the only producer of the material within India.

If the investigation confirms dumping and injury, the DGTR may recommend the imposition of duties to offset the impact and “remove the injury to the domestic industry”. Interested parties have 30 days to submit data and make their representations to the authority.

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