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.

	Control	Struktol HT 300 6 phr	Struktol HT 300 12 phr
Mooney ML (1+4) 100 °C (MU)	75	65	53
Loss of batch weight due to sticking in the mixer (%)	1.9	0.6	0.4

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.      

	Control	HT 300 6 phr	HT 300 12 phr
Hardness	66	67	65
Abrasion loss (DIN)	113	102	106

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!

Japanese chemical manufacturer Tosoh Corporation announced plans on Wednesday to construct a second chloroprene rubber production facility at its Nanyo Complex, representing an investment of approximately ¥75 billion (£460 million) to meet rising global demand for the speciality polymer.

The new facility, scheduled to begin construction in spring 2027, will add 22,000 metric tonnes of annual production capacity for Tosoh’s SKYPRENE chloroprene rubber brand. Commercial operations are expected to commence in spring 2030 at the Shunan City site in Yamaguchi Prefecture.

Chloroprene rubber serves as a critical component across multiple industries, from automotive manufacturing to medical applications. The synthetic rubber’s popularity stems from its exceptional resistance to oil, weather conditions, and flame exposure, making it suitable for demanding applications, including automotive hoses, industrial belts, adhesives, and medical gloves.

The expansion comes as global demand for high-performance polymers continues to grow, driven by increasing automotive production and stricter safety requirements across industrial sectors. Medical applications have also seen increased demand following heightened awareness of the requirements for protective equipment.

Tosoh’s decision to double down on chloroprene rubber production reflects the material’s position within what the company terms its “Chemical Chain Business” - a strategy focused on value-added speciality chemicals rather than commodity products.

The investment represents one of the larger capacity expansion projects announced by Japanese chemical companies this year, signalling confidence in long-term demand fundamentals despite current global economic uncertainties.

The Nanyo Complex already houses Tosoh’s existing chloroprene rubber operations alongside other chemical production facilities. The site’s established infrastructure and logistics capabilities influenced the decision to expand at the existing location rather than develop a greenfield facility.

Industry analysts note that the three-year construction timeline reflects the technical complexity of chloroprene rubber production, which requires specialised equipment and stringent safety protocols due to the chemical processes involved.

The expansion aligns with broader trends in the Japanese chemical industry, where companies are increasingly focusing on high-margin speciality products to offset competitive pressures in traditional commodity chemicals from lower-cost Asian producers.

Epsilon Carbon, a leading global manufacturer of carbon black, has launched N134, which it claims is a specialised ‘Hard Grade’ carbon black known for its superior abrasion resistance and durability.

At present, the high-quality N134 grade is being imported due to the lack of consistent quality and supply chain issues in the Indian market. As a result, the tyre makers have to modify their formulations using other grades of carbon black, which it shared often leads to reduced performance.

But now, Epsilon Carbon has become the first company in India to install a dedicated manufacturing unit designed for N134 grade hard carbon. The company is expanding its existing Vijayanagar Carbon complex facility to produce 215,000 tonnes of carbon black.

This will not only ensure consistent supply of N134 carbon black for tyre makers in the country, reduce import dependency, but also open up export potential to markets such as Europe and USA. Epsilon Carbon will also focus on integrate advanced processing techniques to ensure batch consistency for durability and performance.

Vikram Handa, Managing Director, Epsilon Carbon, said, “This is a proud moment for us and for India’s carbon black manufacturing sector as the high quality N134 black will significantly reduce import dependency and provide tire manufacturers in India and abroad with a reliable, high-quality product. Our goal is to match global standards while building India’s capability to serve premium markets.”

Lummus Technology, a leading provider of process technologies and energy solutions, has signed a memorandum of understanding (MoU) with InnoVent Renewables to collaborate on the global licensing and deployment of InnoVent’s continuous tyre pyrolysis technology.

Under the proposed agreement, Lummus will become the exclusive licensor for InnoVent’s proprietary pyrolysis process, which transforms end-of-life tyres into valuable outputs, including pyrolysis oil, gas, recycled carbon black and steel. Additionally, Lummus will offer integrated technology packages that combine InnoVent’s pyrolysis system with its own downstream processing solutions, enhancing the value of fuel and chemical products derived from waste tyres.

InnoVent’s technology provides a fully scalable, end-to-end solution for converting discarded tyres into renewable fuels and high-value petrochemicals, covering everything from pre-processing to purification. The company currently operates a commercial-scale facility in Monterrey, Mexico, with an annual processing capacity of up to one million passenger tyres, and has the capability to expand further.

Leon de Bruyn, President and Chief Executive Officer, Lummus Technology, said, “This is another significant step in expanding and strengthening our portfolio for the circular economy. By combining InnoVent’s tyre recycling technology with Lummus’ global licensing and engineering expertise, we will be addressing the global challenge of waste tyres and creating new pathways for sustainable product development.”

Vibhu Sharma, Chief Executive Officer, InnoVent Renewables, said, “Partnering with Lummus has the potential to accelerate the global deployment of our technology and help us address the environmental and public health challenges of one billion end-of-life tyres that are disposed of annually. Together, we can transform waste into valuable resources, reduce carbon emissions and support the transition to a more sustainable future.”

Continental is accelerating its efforts to make tyre production more sustainable, with the German tyre manufacturer expecting the share of renewable and recycled materials in its tyres to rise by up to three percentage points in 2025.

The average share stood at 26 percent in 2024, and Continental said it anticipates a further increase this year due to the expanded use of materials such as synthetic rubber derived from renewable sources, recycled PET polyester, recycled steel, and silica made from rice husk ash — a by-product of rice production.

“We are systematically increasing the share of renewable and recycled materials in our raw material portfolio. In five years, we aim to surpass the 40 percent mark,” said Jorge Almeida, Head of Sustainability at Continental Tires. “To achieve sustainable mobility, we are constantly searching for even more environmentally friendly materials. After extensive testing, we integrate them into production as quickly as possible.”

The company has set a goal of using over 40 percent renewable or recycled materials in its tyres by 2030, without compromising on performance or safety.

A key pillar of this transformation is the adoption of mass balance-certified materials. This approach, certified under ISCC Plus, enables Continental to mix certified and non-certified materials during production while maintaining strict accounting procedures to ensure traceability.

The company has already secured ISCC sustainability certification for its tyre plants in Lousado (Portugal), Hefei (China), Púchov (Slovakia) and Korbach (Germany). Continental is also scaling up its use of recycled steel, silica from rice husk ash, and PET yarns made from recycled plastic bottles via its proprietary ContiRe.Tex process.

Other sustainable innovations include COKOON, an adhesive coating system co-developed with Kordsa that replaces formaldehyde and resorcinol in bonding textile components with rubber. Continental also continues to explore alternative additives derived from renewable sources to improve the tyre vulcanisation process.

“We have developed a comprehensive portfolio of diverse, more sustainable materials and are continuously integrating them into all our products after extensive testing,” Almeida said. “In doing so, we ensure that there is no compromise in safety or performance. With this portfolio, we are getting closer and closer to our ambitious, long-term sustainability goals.”