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!

Comments (0)

ADD COMMENT

Link Copied!

Germany's rubber industry continues to face significant headwinds, with fresh data from the German Rubber Industry Association (wdk) revealing a persistent downturn. The figures show employment falling for the fifth year in a row, while production levels have declined for the fourth consecutive year, underscoring the sector's struggle to regain its footing.

The association attributes this stagnation to waning enthusiasm for German rubber goods in both domestic and international markets. Michael Berthel, wdk Chief Economist, described a fundamental shift in procurement behaviour, even within Germany. He noted that purchasing decisions are now driven almost exclusively by price, a stark departure from the historical emphasis on quality and reliability. This change has opened the door to intense international cost competition, placing immense pressure on Germany's medium-sized suppliers. Berthel highlighted that prohibitive domestic costs related to energy, bureaucracy, taxation and labour make it nearly impossible for these firms to compete effectively. Consequently, many are compelled to relocate their investments abroad as a necessary escape from these local burdens, even though their preference would be to maintain and revitalise their operations within Germany after years of strategic transformation.

Against this backdrop, wdk President Michael Klein issued an urgent appeal to the federal government. He acknowledged that the broader struggles of German industry are well documented but stressed the immediate need for decisive political intervention. Klein called for concrete measures to stimulate demand and bolster the nation's competitive edge within Europe without further delay. He warned against allowing the rubber sector to decline quietly, emphasising its critical role in essential areas such as healthcare, infrastructure, security and mobility.

Comments (0)

ADD COMMENT

Link Copied!

Punia Metox Private Limited has commenced production at a new manufacturing facility in Thottambedu, Tirupati, Andhra Pradesh, with operations starting on 12 February 2026.

The plant has an initial production capacity of 12,000 tonnes a year. Its structural design allows capacity to be doubled within four to six months, providing scope for rapid scale-up as demand grows, the company said.

Punia Metox said the facility has been equipped with modern technology to support operational and energy efficiency, safety, sustainability and consistent product quality. The company added that the plant has been designed to enable smooth and seamless operations from the outset.

The expansion forms part of Punia Metox’s strategy to align capacity growth with customer requirements and strengthen its position as a long-term supply partner. The company said the new unit reflects its focus on customer satisfaction, ethical business practices and value-based growth.

Comments (0)

ADD COMMENT

Link Copied!

Cabot Corporation said it can now produce circular reinforcing carbons in the Asia-Pacific region after validating manufacturing capability at its plants in Cilegon, Indonesia, and Tianjin, China.

The materials are produced using tyre pyrolysis oil derived from end-of-life tyres and an International Sustainability & Carbon Certification (ISCC) PLUS mass-balance approach. With the addition of the two Asian sites, Cabot said it now has circular reinforcing carbon production capacity across Asia, Europe and the Americas.

Tyre manufacturers are pursuing targets to increase sustainable material use in tyre production, with many aiming for 40 per cent by 2030 and 100 per cent by 2050, the company said. Cabot’s circular reinforcing carbons are designed as a drop-in replacement for conventional carbon black, allowing manufacturers to increase sustainable content without affecting tyre performance.

Aatif Misbah, Vice-President and General Manager for sustainable solutions in Cabot’s reinforcement materials segment, said: “This achievement reflects our deep commitment to delivering sustainable solutions across Asia Pacific and globally. Scaling our circular reinforcing carbon capabilities helps strengthen our role as a trusted partner to the tire industry, while helping to drive meaningful sustainability progress. Looking ahead, we remain focused on supporting our customers’ evolving needs and helping enable a more sustainable future.”

Cabot’s facilities in Ville Platte, Louisiana; Mauá, Brazil; and Valasske Mezirici in the Czech Republic had previously demonstrated circular reinforcing carbon production capability. The products are ISCC PLUS-certified and marketed under the recovered category of Cabot’s EVOLVE Sustainable Solutions platform.

The company said it has 13 ISCC PLUS-certified sites supporting circular reinforcing carbon production across Asia, Europe and the Americas, along with two certified masterbatch and compounding sites in Europe.

Comments (0)

ADD COMMENT

Link Copied!

The Rathi Group has formalised a partnership with the Indian Tyre Technical Advisory Committee (ITTAC) through a Memorandum of Understanding aimed at advancing technical collaboration on recovered carbon black (rCB). The agreement focuses on the responsible integration of rCB into tyre manufacturing, with an emphasis on detailed evaluation and enhancement of its material properties. This initiative will be driven through structured engagement between industry and academia, supported by ITTAC’s technical expertise.

The collaboration is facilitated by the Automotive Tyre Manufacturers’ Association (ATMA) and ITTAC, which have brought together leading technical experts, tyre manufacturers and research institutions on a unified platform. Their coordinated efforts are fostering a science-based approach to accelerate the assessment and adoption of circular materials within the tyre sector. This partnership is seen as a significant step in strengthening industry–academia linkages to advance sustainable practices.

Through this alliance, the Rathi Group aims to contribute to the evolving landscape of tyre-to-tyre circularity. The joint initiative underscores a shared commitment to developing innovative solutions that support environmental responsibility while maintaining technical performance standards in tyre applications.

Comments (0)

ADD COMMENT

Link Copied!