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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Nynas has played a pivotal role in a landmark achievement for Croatia's energy sector by supplying its advanced NYTRO BIO 300X insulating liquid. This fully renewable fluid has been used for the first time in the Croatian market to fill a 630 kVA distribution transformer. The unit, manufactured by KONČAR – Distribution & Special Transformers, was recently installed in Zagreb for HEP ODS, the national Distribution System Operator.

This collaboration marks the inaugural deployment of a ‘Green Transformer’ in Croatia, representing a significant advancement for the country's distribution network. The project underscores a unified drive towards greater sustainability and a reduced environmental footprint for critical power infrastructure. For Nynas, this milestone highlights the practical application and reliability of its bio-based product portfolio.

NYTRO BIO 300X is engineered to provide a drop-in solution that combines high oxidation stability and superior cooling performance, allowing operators to enhance their ecological standards without compromising on operational reliability or transformer longevity. The successful installation stands as a testament to how industry partnerships are actively accelerating the transition to a more sustainable energy future.

Ivanka Radić, responsible for transformer oils at KONČAR - D&ST, said, “The thermal and dielectric tests on the transformer filled with NYTRO BIO 300X were successfully completed, and the unit is now fully operational. As expected, all test results were within the required limits, confirming the reliability and stability of this innovative fluid.”

Daniele Frustagli, General Manager Italy & the Balkans at Nynas, said, “We are very proud to have been entrusted with this project by KONČAR - D&ST and HEP ODS Zagreb, allowing us to showcase to them and the entire electrical industry the advantages of this fully renewable, bio-based hydrocarbon liquid. In addition to meeting and exceeding the IEC 60296 ed. 5 (2020) specification, the product is readily biodegradable, fully bio-based and has ultra-low viscosity.”

Vanja Burul, President of the Management Board at KONČAR - D&ST, said, “This project reflects our ongoing efforts to explore more sustainable insulating fluids. We see great potential for further use of NYTRO BIO 300X in future applications.”

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Rhodia, the Latin American polyamide leader and a Solvay Group company, has unveiled a major new multi-year investment initiative for its Santo André industrial facility in São Paulo. This strategic programme, valued at BRL 100 million (USD 18.56 million approximately) and scheduled from 2025 to 2028, is designed to drive modernisation, enhance energy efficiency and foster innovation. The funds are allocated for the creation of advanced technologies and an increase in production capacity, with a particular emphasis on high-value-added products. These include smart wires and sustainable solutions that position the national industry at the global forefront.

This substantial investment underscores Rhodia's confidence in the Brazilian market's potential, which is supported by a business environment moving toward greater competitive balance. The company highlights that predictable market rules and effective trade defence measures are crucial for enabling such long-term commitments. By expanding its operations, Rhodia will not only solidify its leadership in polyamide 6.6 production but also advance the spinning processes for polyamide 6. This move is a fundamental step in securing a reliable supply chain and strengthening Brazilian sovereignty, spanning from raw chemical materials to finished part manufacturing. Ultimately, the initiative reaffirms Rhodia's enduring commitment to the national chemical and textile sectors, ensuring enhanced competitiveness and sustained value generation for the local industry.

Daniela Manique, President – Latin America, Rhodia, said, “These investments reflect our confidence in the Brazilian market and its capacity for innovation. We are prepared to offer advanced and sustainable solutions that meet the demands of the dynamic textile sector. We believe that a fair and predictable competitive environment is the main factor for growth, the preservation of skilled jobs and technological development in Brazil.”

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At the recent Reuters Events – Sustainability Europe 2025 conference in London, Birla Carbon’s President and CEO, John Loudermilk, outlined ambitious plans for the company’s circular product, Continua Sustainable Carbonaceous Material. He revealed a strategic vision to significantly expand its availability, with a target for it to eventually comprise up to 10 percent of the company’s global product portfolio. Sourced from end-of-life tyres, Continua SCM is an industrially-produced material designed to offer the same quality, consistency and technical performance as traditional carbon black.

This innovative material allows manufacturers to integrate greater sustainability and circularity into diverse applications such as tyres, plastics and coatings without sacrificing product performance. Loudermilk emphasised that accelerating this transition requires a multi-faceted approach, including supportive regulatory frameworks, deeper collaboration with tyre pyrolysis technology partners and strengthened customer engagement.

Beyond its circular offering, Birla Carbon is also progressing other sustainability initiatives. These include developing carbon black derived from bio-based feedstocks and exploring advanced carbon capture and conversion technologies. These combined efforts support the company’s overarching aspiration to achieve net-zero carbon emissions by 2050, alongside ongoing work to enhance process efficiency and resource utilisation.

Loudermilk said, “While global carbon black consumption typically grows in line with GDP, the demand for sustainable and circular products is increasing at a much faster pace. At Birla Carbon, we see an opportunity to displace up to 10 percent of the carbon black consumption in the world with circular materials like Continua™ SCM, our brand that is derived from end-of-life tyres.”

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Continental has initiated a strategic consolidation of its operations in the United States, which includes the planned closure of its Aldora Mills textile plant in Barnesville, Georgia, by the conclusion of 2026. This decision, impacting approximately 230 employees, follows an extensive review of the company's long-term competitiveness in the Americas. The facility, which produces textile reinforcement materials, including tyre cord fabric, hose yarn and knitted fabric, for exclusive use within Continental’s Tires and ContiTech group sectors, had faced persistent cost challenges for years, with shifting global market conditions ultimately making its continued operation unviable. The company's immediate priority is to provide comprehensive support to the affected staff through career counselling and local employment resources.

Despite this specific closure, Continental is reinforcing its substantial commitment to the US market through continued and significant capital investment. In the past decade alone, the company has directed around USD 1.5 billion into its American manufacturing footprint. This is evidenced by recent projects, such as a major expansion of the ContiTech plant in Mount Pleasant, Iowa and the construction of a new, company-owned tyre distribution centre in the Dallas-Fort Worth area scheduled to open in early 2026.

The company's enduring presence in the country remains robust, with a workforce of over 8,800 people spread across its Tires and ContiTech sectors. Its tyre manufacturing plants located in Illinois, Indiana, Mississippi and South Carolina possess a combined annual production capacity of more than 16 million tyres. The closure of the Aldora Mills facility is therefore presented as a necessary step to safeguard the overall health and future performance of Continental's broader operations across the Americas.

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