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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Taiwan-based performance materials company CHIMEI has secured a distinguished A rating in the CDP Climate Change assessment for the second consecutive year, positioning it within the leading four percent of global organisations evaluated in 2025. This recognition from the prominent environmental disclosure platform underscores the company’s sustained excellence across critical areas such as climate governance, comprehensive risk management and transparent emissions reporting. CHIMEI’s performance demonstrates tangible progress in lowering product emissions intensity, driving self-managed reduction projects and rigorously measuring greenhouse gas outputs in accordance with international standards.

Central to the company’s strategy is its ‘Clean & Green’ vision, which directs a thorough low-carbon transformation. This commitment is operationalised through internal carbon pricing, optimised manufacturing processes and a shift towards renewable energy. CHIMEI further ensures accountability by obtaining third-party verification for the carbon footprints of its entire product range. The pursuit of sustainability extends beyond its own facilities, as the company actively promotes the use of sustainable materials and fosters collaborative decarbonisation efforts throughout its value chain.

Looking forward, CHIMEI is dedicated to engaging with customers, suppliers and partners to advance shared climate objectives, including its ambitious 2050 net-zero target. By continuously investing in innovative technologies and eco-friendly solutions, CHIMEI aims to be a catalyst for industry-wide change, supporting the transition toward a more resilient and low-carbon future for all.

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Kraton Corporation, a leading global producer of speciality polymers and high-value bio-based chemicals derived from pine wood pulping co-products, has achieved International Sustainability and Carbon Certification (ISCC) PLUS for its manufacturing facility in Panama City, Florida, United States. This independent certification tracks sustainable materials via a mass balance approach. The achievement allows Kraton to issue a formal ISCC PLUS Sustainability Declaration with shipments of its biobased polyterpene resins, providing its customers with the documentation needed to validate the renewable content in their own products.

The Panama City site becomes the company’s fourth production plant to gain this certification, building upon a commitment that started with the certification of its Sandarne, Sweden, facility in 2021. By securing these certifications across its network, Kraton strengthens its leadership in supplying circular and renewable solutions. This effort supports broader industry shifts, as customers can now more seamlessly integrate verified, sustainable materials into their supply chains and end products.

Ultimately, the company’s pursuit of such certifications aligns with a larger transition towards a more sustainable and circular economy, demonstrating how specialised chemical producers can enable tangible environmental progress through verified chain-of-custody systems.

Lana Culbert, Kraton Pine Chemicals VP of Marketing, said, “Our SYLVARES™ and SYLVATRAXX™ brands feature a portfolio of high-performance polyterpene resins. They are widely recognised for their use in adhesives and tyre applications, yet their versatility extends to other industries, like agriculture, with more opportunities ahead. While we can measure bio-based content of our pine chemicals using Carbon-14 analysis, certifying our Panama City facility under ISCC PLUS strengthens supply chain transparency, supporting the growth of the circular economy.”

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Solvay has inaugurated its new bio-circular silica facility at its plant in Livorno, Italy, a strategic investment that underscores Italy’s industrial leadership in green innovation. The facility directly anticipates evolving EU sustainability rules for tyres and supports the ambitious environmental goals of Solvay’s customers. By establishing this operation, Solvay positions itself as a proactive partner in achieving the objectives of the European Green Deal and upcoming product regulations.

The site manufactures highly dispersible silica using an innovative process that transforms rice husk ash, an agricultural byproduct, into a valuable bio-based raw material. This method creates a local circular economy, benefits the agricultural sector, and reduces associated CO₂ emissions by 35 percent compared to conventional production.

This initiative is a cornerstone of Solvay's global strategy to transition all its silica production to certified circular raw materials by 2026. While the Livorno site is the first to use rice husk ash, other global plants will utilise different local waste streams. For the tyre industry, adopting this circular silica already enables tyres to contain up to 15 percent recycled or renewable content, providing significant progress towards the sector’s 2030 material targets.

Beyond compliance, the silica produced is essential for developing energy-efficient tyres that lower rolling resistance, thereby reducing fuel consumption and extending electric vehicle range. The Livorno facility thus reinforces Solvay's market leadership in sustainable silica and highlights Italy’s vital role in the company’s broader portfolio of green investments, including projects in green hydrogen and circular soda ash.

Philippe Kehren, CEO, Solvay, said, “By acting now, Solvay is helping tyre manufacturers prepare for future EU requirements and meet their own sustainability goals. Livorno is a tangible example of how we turn circular economy principles into industrial reality, enabling progress for generations.”

Jana Striezel, Head of Purchasing at Continental Tyres, said, "Solvay has managed to transform an agricultural byproduct into a high-performance material on an industrial scale. We are looking forward to integrating more and more rice husk ash silica as a recycled material in our tyre production and are very satisfied with its performance. We are keen on innovative, renewable and recycled materials because they support our ambitious sustainability roadmap.”

An Nuyttens, President of Solvay’s Silica business, said, “Livorno sets a benchmark for circular innovation in Europe and beyond. Our goal is clear: wherever Solvay produces silica, we will integrate circular materials to reduce environmental impact and support our customers’ sustainability objectives.”

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Ecolomondo Corporation, a Canadian developer of sustainable technology for recycling scrap tyres, has announced that its Hawkesbury facility reached a key operational milestone during the week of 12 January 2026, by successfully completing a record five double processing batches. This progress signifies a major step forward as the company advances towards full commercial production at the plant. Utilising its proprietary Thermal Decomposition Process (TDP) and a new automated Human-Machine Interface system, the facility maintained consistent operations and produced high-quality recovered materials.

The week’s activity led to the recycling of an estimated 9,375 scrap tyres, processing a total of 150,000 pounds (approximately 68,038 kg) of rubber feedstock. From this, approximately 60,000 pounds (approximately 27,215 kg) of recovered carbon black and 75,000 pounds (approximately 34,019 kg) of tyre-derived oil were generated, alongside syngas used to power the process itself.

As a Canadian leader in tyre recycling technology, Ecolomondo views these results as a strong validation of the scalability and reliability of its proprietary TDP system, underscoring the ongoing ramp-up at its Hawkesbury TDP facility. This consistent performance enhances the company's position in the circular economy, turning a challenging waste stream into valuable industrial commodities and demonstrating the commercial viability of its innovative approach.

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