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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Tokyo Zairyo Co., Ltd., a wholly owned subsidiary of Zeon Corporation, marked a significant milestone in November 2025 by establishing a new branch office in Chennai, Tamil Nadu, India. Following the completion of all necessary preparations, this location has now commenced full-scale operations. The move represents a deliberate effort to broaden the company’s commercial reach across the Indian market while simultaneously constructing an organizational structure capable of responding with greater agility to the evolving and increasingly diverse requirements of its customers.

This southern expansion comes approximately 15 years after the company first established its Indian subsidiary, Tokyo Zairyo (India) Pvt. Ltd., with an office in Gurugram, Haryana, in 2011. By positioning a second office in Chennai, the firm now operates a coordinated network spanning the northern and southern regions of the country. Close collaboration between the two locations is intended to strengthen information services and enhance user support, leveraging both internal capabilities and external partnerships to better serve Japanese automotive parts manufacturers and processors operating throughout India.

Through this dual-office structure, Tokyo Zairyo is poised to advance its core business of purchasing and selling a broad spectrum of materials, including rubber, resins and elastomers. The synchronised operations in Gurugram and Chennai enable the company to deliver more responsive support, ensuring that clients across the Indian automotive supply chain benefit from efficient service and a reliable supply of essential materials.

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Kuraray Co., Ltd. has announced a comprehensive global price adjustment for its portfolio of Liquid Rubber products and ISOBAM alkaline water-soluble polymer. These changes, which are set to take effect on 16 April 2026, will see prices rise by at least USD 2 per kg.

The driving forces behind these significant pricing actions are multifaceted, rooted in substantial disruptions to global supply chains. These disruptions are largely attributed to the ongoing conflict in the Middle East, which has had a cascading effect on logistics. Compounding this issue are the sharply rising costs associated with transportation and essential raw materials.

This strategic move is essential for the company to maintain operational stability and continue the supply of Liquid Rubber and ISOBAM amidst the volatile market conditions.

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German chemical group WACKER has announced a price hike across its silicones product range, responding directly to significant upheavals in international commodity markets triggered by the recent military conflict in the Middle East. This geopolitical instability has created pronounced distortions throughout the supply chain, leading to a sharp escalation in the costs of essential inputs. The company is experiencing substantially higher prices for energy as well as for various other raw materials and logistics services.

To address this challenging economic landscape and offset the considerable burden of increased raw material and transportation expenses, the chemical group is implementing price adjustments effective 1 April 2026. The updated pricing will be communicated to the customers accordingly. This strategic move is essential for the company to maintain operational stability and continue delivering its products reliably amidst the volatile market conditions.

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Scandinavian Enviro Systems AB publ has signed a letter of intent with an undisclosed partner to explore the possibility of licensing its advanced tyre pyrolysis technology for deployment in North America.

The collaboration will focus on conducting a comprehensive feasibility study to evaluate the technical and commercial viability of establishing one or multiple facilities dedicated to processing end-of-life tyres using Enviro’s proprietary method. This study is designed to provide the potential licensee with the necessary insights to assess the prospects of entering into a long-term commercial arrangement and formal technology licensing agreement.

It is important to note that any definitive agreements will depend entirely on the study's outcomes and subsequent negotiations. At this stage, there is no guarantee that the evaluation will lead to binding commitments or that the proposed transaction will ultimately materialise.

Fredrik Aaben, CEO, Scandinavian Enviro Systems, said, “We continue to see strong international interest in Enviro’s technology, and this letter of intent is yet another proof of this.”

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