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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Orion S.A., a global speciality chemicals company, has successfully secured the prestigious ISCC – the International Sustainability and Carbon Certification for its manufacturing facility located in Qingdao, China. This significant achievement is the direct result of a rigorous, independent audit process which validated that the plant’s operations fully comply with the comprehensive sustainability criteria established by ISCC.

The certification serves as a formal verification of both the transparency and the complete traceability of the sustainable raw materials integrated into the facility’s production value chain. This milestone is a key component of Orion’s overarching corporate strategy to implement and enhance sustainable practices throughout its international operations.

By achieving this globally recognised standard, the company reinforces its commitment to supplying clients with high-performance carbon black and other speciality chemical products that adhere to leading international environmental and sustainability benchmarks, thereby supporting customer goals for more responsible manufacturing.

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Ecolomondo Corporation, a Canadian developer of sustainable technology for recycling scrap tyres, has secured a provisional financing agreement with Export Development Canada (EDC) for USD 2.7 million. The funds are intended to support the final ramp-up phase of its Hawkesbury thermal decomposition plant by covering necessary capital investments and operational working capital.

Following months of negotiation, both parties have agreed in principle to the loan terms, which include augmenting an existing USD 2 million credit facility established by a subsidiary, Ecolomondo Environmental (Hawkesbury) Inc, in January 2025.

Furthermore, EDC has conditionally approved a temporary suspension of principal and interest payments for loans from 2024 and 2025, applicable during the facility's 2026 ramp-up period. This financial arrangement is designed to provide the liquidity required to advance the project to full operational capacity, pending the finalisation of formal documentation.

Jean-François Labbé, Interim CEO, Ecolomondo Corporation, said “We have been working steadily in Hawkesbury, hiring, training, increasing production, increasing sales and, most of all, improving efficiency. This additional financing from EDC is greatly appreciated and should allow the Hawkesbury TDP facility to achieve its full potential.”

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Cabot Corporation said it has received improved environmental ratings from CDP, reflecting continued progress in water management and steady performance on climate disclosures.

In CDP’s 2025 assessment, the company was awarded an A- rating for Water Security, up from a B in 2024, and a B rating for Climate Change, unchanged from the previous year. Cabot said the water score exceeded both global and industry averages, recognising its approach to managing water-related risks and implementing sustainable water practices.

The Climate Change rating remained stable year on year, with improvements reported in areas including climate risk disclosure, value chain engagement and industry collaboration.

The latest scores extend a five-year pattern of incremental improvement, achieved amid more demanding reporting standards and rising expectations from regulators, investors and customers.

“We are proud that CDP’s independent assessment reflects our ongoing efforts to enhance environmental performance and transparency,” said Jennifer Chittick, senior vice-president for Safety, Health and Environment and chief sustainability officer. “The improvement in our Water Security score demonstrates our leadership in this critical area, and we remain committed to advancing our sustainability strategy across all domains. This progress was made possible by our dedicated, global team, and we remain focused on driving further improvements in the years ahead.”

CDP assesses companies on environmental impact across climate change, water security and deforestation, using a scale from D for Disclosure to A for Leadership. In 2025, more than 24,800 companies were rated, representing about two-thirds of global market capitalisation.

Cabot said the results underline its focus on transparency and responsible environmental management as it continues to execute its sustainability strategy.

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A USD 1.4 million equipment enhancement at Liberty Tire Recycling’s Cameron, North Carolina, facility is set to significantly boost its processing capabilities. This upgrade, enabled by the state’s sustainable financial backing of its scrap tyre programme, will allow the facility to handle an extra 3,300 tonnes of material annually, representing nearly 300,000 passenger tyres.

A key improvement is the increased capacity to process truck tyres, which are more challenging to recycle due to their size and durable steel components. The resulting crumb rubber, highly sought after by manufacturers, will be directed towards producing floor mat bases and rubber tiles made entirely from recycled material. This material also serves as a component for athletic tracks, synthetic turf, rubberised asphalt and various moulded products.

This capital investment follows North Carolina’s legislative action to redirect tyre disposal fees into the state’s scrap tyre management system, a move that includes compensating counties for collection and recycling expenses. With North Carolina establishing itself as a centre for tyre recycling, Liberty Tire indicates it is evaluating further multi-million-dollar investments and job creation across its other operations in the state.

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