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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HS HYOSUNG has formalised a memorandum of understanding (MoU) with the State Government of San Luis Potosí, with the signing taking place at the World Trade Center Mexico City. The event formed part of the Korea-Mexico Business Forum, held alongside the Korean economic delegation's visit to Mexico.

Attending officials included Marcelo Ebrard, Mexico's Secretary of Economy, and Mario García Valdez, Secretary of Economic Development of San Luis Potosí. The two sides confirmed their shared resolve to back the company's local investment and regional growth. Separately, HS HYOSUNG's leadership met bilaterally with Secretary Ebrard to elaborate on its strategic vision and investment plans.

The agreement sets out a phased expansion of HS HYOSUNG's investments in San Luis Potosí beginning in 2027, with the goal of creating a major advanced materials production hub that bolsters supply for North American and wider global markets. The company's advanced materials span tyre cord, a flagship world-leading product, along with mobility, energy, aerospace and defence applications. Its North American operations, spanning Mexico and the United States, turn out tyre cord, airbag materials and mobility interior components for global leaders such as General Motors and Goodyear, underpinned by a highly dependable global supply chain.

Nak-yang Sung, CEO, HS HYOSUNG ADVANCED MATERIALS, said, “This investment goes beyond establishing a simple manufacturing base – it reflects our strategy to turn Mexico into a pivotal hub connecting North America with global supply networks. We are also committed to strengthening local supply chains and creating high-quality jobs to contribute directly to the region's industrial ecosystem.”

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Kumho Petrochemical Group is steering its business towards research-driven, higher-value outputs as oversupply and soft demand continue to weigh on the worldwide petrochemical sector. The Seoul-based group outlined plans to boost spending on speciality chemicals, sustainable materials and novel production methods, a push intended to lift profits while building a foundation for future expansion.

Underlying the move is a deliberate evolution in the group's identity, from a bulk materials vendor to a provider of technology-backed solutions that address shifting customer requirements and stricter environmental rules. A central element of that effort involves widening the speciality lineup, exemplified by added capacity for solution styrene butadiene rubber, a synthetic rubber that enhances durability, rolling resistance and tread wear in high-performance electric vehicle tyres.

Environmental initiatives form another pillar. Facilities built by the company can trap approximately 76,000 metric tonnes of carbon dioxide each year, while separately developed technology turns recycled acrylonitrile butadiene styrene sourced from scrapped household appliances into automotive-grade interior components that satisfy performance standards and generate fewer emissions than conventional methods. The group has also joined forces with POSCO Future M and BEI on anode-free lithium-metal battery development.

Parallel technology-focused programmes are underway at affiliated units. Kumho P&B Chemicals is formulating water-based epoxy resins that curb volatile organic compound releases while incorporating more bio-based inputs to reduce carbon intensity. Kumho Mitsui Chemicals is advancing bio-based polyurethane systems and electric vehicle materials, alongside debottlenecking work to add 100,000 tonnes of annual methylene diphenyl diisocyanate capacity. Kumho Polychem, meanwhile, is targeting ethylene propylene diene monomer through low-temperature polymerisation paired with energy-efficiency improvements.

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Birla Carbon has confirmed a price increase of up to 15 percent for its Speciality Materials products across Asia, scheduled to take effect on 1 October 2026. The company pointed to significant and sustained rises in feedstock costs, driven partly by ongoing geopolitical instability and disruptions in global feedstock markets, as the reason behind the adjustment.

Although Birla Carbon pursued operational efficiencies, supply chain optimisation and disciplined cost management to soften the impact, the scale and persistence of the cost escalation left a price adjustment unavoidable. The company's sales teams will engage customers directly to explain the details and help them navigate the transition.

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ACE Laboratories, an independent ISO/IEC 17025-accredited polymer testing laboratory, has partnered with Abdallah Consulting, LLC, a prominent tyre pyrolysis advisory firm, to introduce VericarbSM. This independent certification programme verifies that materials marketed as recovered carbon black (rCB) meet established criteria for rCB.

Recovered carbon black, derived from end-of-life tyres via pyrolysis, serves as a sustainable substitute for virgin carbon black in rubber and polymer applications. However, the emerging market has lacked the standardisation and independent verification that established supply chains provide. VericarbSM addresses this gap through independent material characterisation and rubber performance data, offering stakeholders a consistent basis for evaluating rCB products.

For producers, certification accelerates market entry and improves buyer approval rates. Consumers gain more capable suppliers and reduced evaluation time, while investors benefit from clearer volume sizing and fewer costly test failures. The programme is jointly administered by both organisations.

Erick Sharp, CEO, ACE Laboratories, said, “The rCB market has enormous potential, but growth has been held back by uncertainty about material quality and consistency. VericarbSM gives producers a way to prove their product and gives buyers the independent data they need to say yes.”

Dave Abdallah, Founder, Abdallah Consulting, said, “One key reason for the delayed growth of recovered carbon black is lack of product performance information in the customer’s language. ASTM standards are critical; in fact, most testing done in the process follows ASTM methods. But customers relate to a product better when its performance is shown in applications relevant to them. VericarbSM solves the language issue by showing verified rCB in terms of rubber performance while simultaneously adding credibility via third-party analysis and reporting.”

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