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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Solvay is expanding its global circular economy strategy by converting its Asian production of highly dispersible silica (HDS) to use certified circular raw materials. Beginning in 2026, its plants in Qingdao, China, and Gunsan, South Korea, will transition to using ISCC+ certified waste sand. This major initiative is projected to make over half of the region’s HDS output circular, directly aiding tyre makers in their goal of incorporating over 40 percent sustainable materials by 2030.

This transition provides tyre manufacturers with a cost-effective, high-volume circular Zeosil silica that integrates seamlessly into existing processes without the need for reformulation. The move builds on the successful conversion of Solvay’s Livorno, Italy, facility to using rice husk ash and reflects a coordinated, global shift towards circular sourcing. It also supports the broader sustainability goals of Solvay Silica, including the adoption of low-emission technologies like electric furnaces to minimise the carbon footprint of its products worldwide.

By pioneering circular silica from diverse feedstocks and regions, Solvay is fostering more resilient and sustainable supply chains through innovative partnerships across the entire value chain.

An Nuyttens, President of Solvay’s Silica Business unit, said, “Solvay’s circular silica helps improve fuel efficiency and EV range, offers long-lasting wear benefits, improves safety, while advancing sustainability. This is more than innovation - it’s a reinvention of how we source, produce and collaborate across the value chain.”

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Following the formal approval of its foundational design, Sinopec has announced the construction of a new green, high-end rubber materials facility in Tianjin, China. The project, which was initially revealed in 2023, represents a total investment of CNY 2.452 billion (approximately USD 344.65 million). Its production output will include 100 kilotonne per annum (ktpa) of solution styrene butadiene rubber and an equal volume of nickel-based butadiene rubber.

Operated by Sinopec’s Beijing Yanshan branch, the venture will be funded through a combination of 70 percent bank loans and 30 percent company capital. The initial construction phase, focused on piling work for processing units, storage areas and auxiliary facilities, is valued at CNY 28 million (approximately USD 3.94 million) and scheduled for completion within 31 days.

This new rubber plant is an integral component of the larger Sinopec Nangang high-end materials industrial cluster, which also features a recently completed 1.2 million tonne-per-year ethylene complex. Encompassing a 277,004 sqm site with a built area of 43,522 sqm, the facility is projected to become operational in 2027.

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Elkem ASA, a global leader in advanced silicon-based materials, has announced a significant advancement in silicone sustainability with the successful validation of a new mechanical recycling process for High Consistency Rubbers (HCR). This innovation provides a scalable method for recycling crosslinked HCR waste and reintroducing it into new product formulations. The process achieves re-incorporation rates of over 50 percent while maintaining the excellent mechanical properties required for high-performance applications. This breakthrough demonstrates how material engineering can enable a more circular economy for silicones, helping to reduce waste and the carbon footprint while meeting rising market demand for sustainable solutions.

This mechanical recycling process expands Elkem's comprehensive silicone recycling strategy, which now encompasses both chemical and mechanical pathways. The ability to integrate multiple recycling technologies allows the company to tailor its approach based on the type of waste material, specific carbon reduction goals and the performance needs of the final product.

The development is a key outcome of the open innovation project ‘RENOV’ (Recycling & Reincorporation of Elastomer Materials), focused on creating technologies for recycling and reincorporating crosslinked elastomer waste. The project, supported by the French environment agency ADEME, unites Elkem with industrial partners Hutchinson and Nexans, as well as several CNRS-affiliated laboratories. A primary objective is to evaluate market acceptance and identify the most promising commercial and environmental applications for mechanically recycled HCR.

High Consistency Rubbers are valued for their exceptional strength, thermal stability and electrical insulation properties, making them critical components in industries ranging from electric vehicles and aerospace to medical devices and electronics. Elkem will present samples of the recycled material and detail this new technology at the K 2025 trade fair in Düsseldorf, Germany, from 7–14 October 2025.

Joséphine Munsch, R&T sustainability leader at Elkem, said, “This breakthrough demonstrates the power of purpose-driven innovation aligned with market expectations. After two years of development, we are proud to present a first proof of concept for mechanical recycling of HCR, opening the door to new industrial applications and reinforcing our ambition to leverage pragmatic, science-driven solutions to lead and accelerate the transition to a circular economy for silicones.”

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ContiTech, a group sector of Continental, has officially launched production at its new USD 90-million hydraulic hose manufacturing facility in Aguascalientes, Mexico. This significant investment is a strategic move to reinforce local supply chains, boost regional production capacity and position innovative fluid power solutions closer to its customer base across North America.

The new 900,000-square-foot plant will produce high-performance hoses for numerous industrial and mobile applications, serving vital sectors such as construction, agriculture, mining and energy. It has been designed to operate in a tightly coordinated network with ContiTech’s existing facility in Norfolk, Nebraska. This dual-plant strategy enhances production flexibility, improves operational efficiency and allows the company to be more responsive to evolving customer demands by strategically balancing technology, volume and lead times.

This expansion underscores ContiTech's long-term commitment to growth in key markets through substantial investment in local infrastructure and talent. Production at the Aguascalientes site will be gradually increased, with the first customer deliveries anticipated to commence in the fourth quarter of 2025.

Philip Nelles, Member of the Continental Executive Board and CEO of the ContiTech group sector, said, “The start of production in Aguascalientes marks a key milestone in ContiTech’s journey towards being a more agile, regionalised partner to our customers. At ContiTech, we build on 150 years of materials expertise. While our portfolio is broad and diverse, all our solutions are grounded in the same strength: high-performance materials that are mission critical, innovative and engineered to perform. Whether they connect, convey or cover, our products play essential roles across industries and applications.”

Andreas Gerstenberger, CEO of ContiTech USA and Head of Business Area Industrial Solutions Americas, said, “We are ready to lead in this segment. This new plant reflects our commitment to both innovation and proximity. With our customers increasingly looking for responsive and innovative solutions, we are proud to deliver with local production, advanced technology and a skilled workforce. More than just expanding our footprint, this investment is about creating mutual value with our customers, partnering closely to help them succeed in their own markets. By placing customer needs at the centre of everything we do, we aim to be their first choice for material-driven solutions, now and in the future.”

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