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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Birla Carbon Spain has been awarded a EUR 2 million grant by the Society for Regional Development of Cantabria S.A. (SODERCAN), a public entity of the Government of Cantabria, to advance an energy autonomy initiative at its Cantabria plant. The funding announcement was made in late February during a visit attended by María José Sáenz de Buruaga, President of Cantabria; Eduardo Arasti, Minister of Industry, Employment, Innovation, and Trade of Cantabria and Ángel Pedraja, CEO of SODERCAN. The grant forms part of a broader investment project by Birla Carbon Spain aimed at strengthening energy self-sufficiency at the facility.

The funding will support the installation of a 4 MW back-pressure steam turbine at the Cantabria unit, enabling it to generate electricity and steam internally for operations. When completed, the project is expected to reduce CO2 emissions annually while also decreasing reliance on water from the Miera River for cooling purposes and reducing process water discharge. Beyond these environmental benefits, the investment will help safeguard nearly 200 direct and indirect jobs associated with the facility, reinforcing the company's commitment to both sustainability and regional economic stability.

During the visit, President María José Sáenz de Buruaga was briefed on the technical and environmental aspects of the project and described it as a collective success. She recognised Birla Carbon Spain's strategic role in the regional industrial ecosystem and its position as a benchmark for innovation in Europe. The initiative represents a significant step towards sustainable manufacturing practices while demonstrating the company's dedication to long-term operational viability and environmental stewardship in Cantabria.

Dale Clark, Chief Manufacturing Officer, Americas & EMEA, Birla Carbon, said, “We were honoured to welcome the President of Cantabria, the Minister of Employment, Innovation and Trade of Cantabria and the CEO of SODERCAN to our Cantabria plant. Their support reflects the strategic importance of our operations to the region and the industries we serve with our carbon black solutions. The steam turbine will be key in helping the plant achieve energy autonomy, reducing our carbon footprint and strengthening long-term operational resilience. At Birla Carbon, we also remain continuously focused on improving energy efficiency, reducing water consumption and advancing sustainable manufacturing practices across our global operations.”

María José Sáenz de Buruaga, President of Cantabria, said, “With this contribution, not only does Birla Carbon win, but Cantabria wins too, because we are making decisive progress in the transformation of our production model and in our commitment to industrialisation.”

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Flexsys, a global leader in advanced tyre additives and material-science solutions, has been honoured with the Chemical and Compounding Innovation of the Year Award at the Tire Technology International Awards for Innovation and Excellence. This recognition celebrates the company’s progress in creating a novel alternative to 6PPD for tyre manufacturing.

Driven by a significant challenge within the tyre industry, Flexsys’s dedicated research and development team, alongside respected federal and independent laboratories, pursued the creation of a next-generation replacement for 6PPD. Their investigation spanned hundreds of molecules from various chemical families, ultimately identifying several promising candidates that satisfy the stringent criteria for both tyre efficacy and environmental safety. Extensive laboratory testing, conducted both internally and by external parties, has confirmed that one of these candidates delivers robust antidegradant qualities while presenting a favourable toxicological profile. Significantly, this effective molecule is not a PPD chemical. Currently, performance trials are in progress with selected industrial collaborators, with further information regarding the specific molecule anticipated later this year.

The award itself is determined by a completely autonomous international jury composed of journalists and industry specialists. It is coordinated by Tire Technology International magazine, a publication owned by UKi Media & Events, which also organises the renowned Tire Technology Expo.

Neil Smith, Chief Technology and Sustainability Officer, said, “We are honoured to receive this industry recognition for our work, which reflects our commitment to delivering solutions that meet demanding performance requirements while advancing environmental responsibility. I’m incredibly proud of the Flexsys R&D team whose dedication and scientific rigor has allowed us to achieve this recognition. We believe collaboration across the tyre and materials ecosystem is essential to developing durable, scalable solutions for the industry and look forward to continuing this journey together.”

Matt Ross, Editor-In-Chief, Tire Technology International magazine, said, “The Tire Technology International Awards for Innovation and Excellence are recognised as the industry’s top accolades and aim to celebrate the best new technologies and innovations from all over the world. On behalf of all of the judges, we extend our congratulation to the Flexsys team on this win and their work to find a replacement for 6PPD in tyres.”

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Pyrum Innovations AG has announced an immediate update to the nomenclature of its recycled material outputs as part of a strategic effort to reinforce its brand identity and underscore the distinctiveness of its offerings. The company’s thermolysis oil, formerly referred to as recycled oil, will now be designated TTO (ThermoTireOil). Similarly, what was previously known as recovered Carbon Black (rCB) will adopt the new name TTB (ThermoTireBlack).

This decision stems from inconsistencies observed across the broader market for recycled commodities. Materials sold under generic labels such as rCB or pyrolysis oil often vary significantly in composition, largely because they may contain residual additives or lack standardisation. In the case of rCB, for instance, the presence of inorganic elements from tyres can lead to blends that are unsuitable for certain high-performance applications. Pyrum’s output, by contrast, is produced through its patented thermolysis technology, which yields materials with a consistent and well-defined makeup. The new names are intended to reflect this precision and set them apart from less uniform alternatives.

The underlying production process remains centred on breaking down end-of-life tyres into their constituent elements. TTB has already entered series manufacturing in the tyre industry and is gaining recognition for use in products such as conveyor belts, seals, and protective coatings. TTO, meanwhile, functions as a renewable input for polymers used in clothing, automotive components and food-safe packaging.

Rollout of the new terminology begins at once and will be phased into all technical records, official certifications and customer communications. Although the labelling is new, the formulations and quality levels of the products themselves are unchanged.

Pascal Klein, CEO, Pyrum Innovations AG, said, “Our products are the result of years of development and intensive research. With the new designations TTO and TTB for our oil and our rCB, we make it clear that these are unique materials obtained from our unique thermolysis process.”

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KRAIBURG TPE has earned gold medal from EcoVadis for the second consecutive year. This recognition reflects the performance of the company’s entire global operations, which collectively achieved this distinguished honour. The company posted new peak scores across all four evaluation categories, which include environmental impact, labour and human rights, ethical conduct and sustainable sourcing. Ranking in the 98th percentile, KRAIBURG TPE now stands among the top two percent of all companies rated by EcoVadis globally, reinforcing its status as a frontrunner in responsible corporate practices.

Within the plastics sector, sustainability has evolved into a fundamental driver of success. Growing public attention now extends beyond isolated topics, calling instead for businesses to offer clear and reliable sustainability reporting. Measurable indicators that track advancements and allow for objective comparisons across industry peers have thus become indispensable.

Having evaluated over 150,000 businesses, EcoVadis has cemented its role as one of the most trusted frameworks for assessing corporate sustainability. The benchmarks applied by the Paris-based organization across its categories are both rigorous and comprehensive. Given this demanding standard, KRAIBURG TPE’s 2022 achievement of a silver award in its debut year was particularly meaningful.

In 2025, the company reached a new milestone by receiving its first gold medal covering all global facilities, a testament to inter-site collaboration and the dedication of its entire workforce. This distinction was reaffirmed during the scheduled reassessment in January 2026, accompanied by even higher marks in every category. Such ongoing improvement demonstrates the company’s steadfast commitment to advancing its sustainability objectives consistently across international operations.

Oliver Zintner, CEO, KRAIBURG TPE, said, “For us, this second Gold Award is confirmation in many respects of the extraordinary achievements we have made in the field of sustainability in the past years. On the one hand, it demonstrates how strong our position is in international comparison. But above all, the award emphasises how continuously and persistently we pursue our sustainability goals in all categories. Results like that are not at all a matter of course in our competitive environment. They only become possible because our colleagues at all sites worldwide are closely working together in a partnership-based manner.”

Michael Pollmann, Sales & Marketing Director EMEA, said, “In addition to product quality, price and delivery reliability, sustainability criteria are a more and more important factor for our customers’ purchase decisions. The EcoVadis award represents the consistency and transparency with which we implement our sustainability promises. It is a relevant strategic competitive factor and is gaining in importance, particularly in view of increasing legal requirements in fields such as supply chain assessment.”

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