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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Kraton Corporation, a leading global producer of speciality polymers and high-value biobased products derived from pine chemicals, has unveiled a comprehensive new suite of long-term sustainability goals. These ambitious 2032 targets, which build upon the company's established record of environmental stewardship, focus on substantial reductions in carbon emissions, water consumption and waste generation. This initiative underscores Kraton's strategic commitment to fostering a sustainable business that delivers lasting value.

The new objectives were formulated following an extensive internal assessment of emissions and resource efficiency. This detailed evaluation included energy audits and site-specific reviews of water and waste, resulting in a robust framework designed to solidify Kraton's position as a leader in the transition toward a low-carbon and resource-conscious economy. By 2032, the company aims to achieve a 30 percent absolute reduction in its direct and indirect (Scope 1 & 2) greenhouse gas emissions, alongside a 30 percent intensity reduction in emissions from its supply chain (Scope 3.1). Further goals include a 10 percent intensity reduction in both water use and waste production.

This environmental strategy is intrinsically linked to Kraton's product innovation. The company is expanding its portfolio of sustainable solutions, supported by lifecycle assessment data and third-party certifications like ISCC PLUS, to assist its customers in minimising their own environmental footprint. Kraton's dedication to corporate responsibility has been consistently recognised, evidenced by its receipt of the EcoVadis Platinum rating for the fifth consecutive year, highlighting its ongoing advancement in sustainability management and performance.

Marcello Boldrini, Chief Executive Officer, Kraton, said “At Kraton, sustainability is the foundation of how we create value, innovate and lead for the future. These new long-term targets reflect our commitment to drive meaningful impact across our operations and value chain while supporting our customers in achieving their own sustainability goals.”

Rogier Roelen, Chief Sustainability Officer & General Counsel, Kraton, said “Our new targets are designed to meet our customer expectations for transparency, innovation, upstream raw material decarbonisation and resource efficiency while maintaining the flexibility needed to support business growth. Kraton’s supplier engagement programme will be instrumental in achieving our goals, and we will continue to collaborate closely with our partners to drive progress together.”

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In a strategic move to bolster its international presence, HS HYOSUNG ADVANCED MATERIALS is establishing a new production subsidiary in India. The company will invest USD 30 million to form HS Hyosung India Private Limited, located in the industrially significant state of Maharashtra. This region is an economic powerhouse within India, making it an ideal location for the new tyre cord manufacturing plant, which is scheduled to be operational by 2027.

This significant investment is a direct response to India's emergence as the world's third-largest automobile market. The country's ongoing infrastructure development and a rapidly expanding logistics sector are creating a surge in demand for tyres, and consequently, for the materials used to make them. By localising production, the company aims to build a more resilient supply chain, increase its market share and respond more dynamically to the needs of the Indian market. The facility, situated on a 230,000-sqm site in the Nagpur Industrial Complex, is planned not only for tyre cord production but also for future expansion into other product lines like airbag fabrics.

As the global leader in polyester tyre cord manufacturing for over two decades, HS HYOSUNG ADVANCED MATERIALS commands approximately half of the worldwide market share. These cords are critical reinforcement components inside tyres, enhancing their safety, durability and overall performance. The company supports its market position with a global production and research network spanning Vietnam, China and United States. It is also actively innovating to meet new mobility demands, having created advanced products such as high-strength and high-modulus tyre cords tailored for electric vehicles, which has solidified its reputation with major tyre producers globally.

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According to a recent analysis by the International Rubber Study Group (IRSG), an inter-governmental organisation composed of rubber producing and consuming stakeholders located in Singapore, India's rubber industry demonstrated robust performance in the first half of 2025. The sector saw demand for both natural and synthetic rubber continue to outpace supply. Natural rubber consumption grew by 2.1 percent against a 1.9 percent production increase. The synthetic rubber market expanded even more rapidly, with consumption rising 5.6 percent and production increasing 5.4 percent.

The automotive tyre industry remains the primary market force, consuming 62.8 percent of all natural rubber and 68.9 percent of synthetic rubber. This sustained demand from tyre manufacturers occurred alongside mixed vehicle sales figures. While passenger car sales experienced a slight decline of 0.1 percent, this was counterbalanced by healthy growth in the two-wheeler and three-wheeler segments, which increased by 0.9 percent and 6.5 percent, respectively.

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The Association of Natural Rubber Producing Countries (ANRPC) has released its Monthly NR Statistical Report for September 2025, providing an overview of key developments in the global natural rubber sector.

The ANRPC Statistics and Information Committee (ISC) presented an updated perspective on the global supply-demand landscape for 2025 and examined updated 2024 statistics and growth rates during the October 2025 Annual Assembly Sessions. September saw price volatility and pressure as output increased while demand stayed low. However, tapping activities were limited in several producing regions due to rains and labour limitations, which contributed to a passive production rise that was not anticipated during the peak production season.

Global natural rubber (NR) output is expected to increase slightly by 1.3 percent in 2025 compared to 2024, according to recent reports from ANRPC member nations, after Indonesia's production base was revised downward. Concurrently, it is anticipated that NR demand would increase by 0.8 percent in 2025 due to an increase in Indonesia's consumer base. Although there were some indications of recovery in the tyre sector in a few countries, market mood remained divided.

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