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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The Association of Natural Rubber Producing Countries (ANRPC) confirmed the participation of its Secretary-General, Dr Suttipong Angthong, in a high-level dialogue held on 9 July 2026. The engagement took place during the official visit of Thailand's Prime Minister, His Excellency Anutin Charnvirakul, to Malaysia. Dr Angthong joined a prominent assembly that included the Prime Minister, Thailand's Deputy Prime Minister and various cabinet delegates from both nations.

The meeting also brought together representatives from international intergovernmental bodies and leading corporate figures from Thai and Malaysian industries. Given that both Thailand and Malaysia are founding members of the ANRPC and serve as cornerstones of the global natural rubber market, the session was deemed a crucial venue for harmonising regional strategies. It offered the ANRPC a platform to elevate sector-specific priorities within top-tier governmental discussions.

Through the facilitation of productive exchanges between policymakers and private-sector leaders, the ANRPC continues to foster cross-border collaboration, reinforce the stability of supply chains and advance sustainable growth initiatives. The organisation has reiterated its steadfast dedication to supporting its member states with professionalism and collaborative effort, aiming to secure the long-term vitality and resilience of the natural rubber industry across the region.

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The Association of Natural Rubber Producing Countries (ANRPC) hosted a high-level delegation from PEFC International at its headquarters on 9 July 2026. The visiting team, led by Remco van Merm, engaged in strategic talks with ANRPC Secretary-General Dr Suttipong Angthong and his senior staff, marking a significant moment for inter-organisational collaboration.

The discussions provided a critical forum for exchanging perspectives on ongoing global initiatives and the shifting sustainability dynamics affecting the natural rubber sector. With mounting market pressures regarding environmental stewardship and social accountability, the conversation centred on harnessing joint efforts to fast-track the implementation of responsible practices throughout the entire production and distribution network.

Both organisations underscored the necessity of strengthened coordination among all industry participants to secure a robust and enduring future for natural rubber. The dialogue culminated in a shared pledge to deepen cooperation, with the goal of cultivating a more transparent and ecologically sound value chain. This mutual commitment is expected to deliver tangible benefits across the board, reinforcing the industry's capacity to meet emerging global standards.

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Natural Rubber (NR) plantations developed under Project INROAD (Indian Natural Rubber Operations for Assisted Development) have reached 179,376 hectares across north-east India after the completion of planting for the 2025-26 financial year, bringing the initiative close to its original target of 200,000 hectares.

Launched in the 2021-22 financial year, the project has established new NR plantations across 113 districts in the region over the past five years. According to the project partners, this represents the country's largest expansion of natural rubber plantations achieved within such a period.

Project INROAD is funded by tyre manufacturers Apollo Tyres, CEAT, JK Tyre and MRF, and is implemented by the Rubber Board of India. It is described as the first initiative of its kind in which the Indian tyre industry directly supports the development of rubber plantations.

"Despite several operational challenges including Covid-induced disruptions in the beginning, nearly 90% of the ambitious target of 2 lakh hectares of new plantation has been achieved under Project INROAD during the last five years. Beyond plantation expansion, the project has also made significant progress in strengthening local nurseries and building grower capacities — a testament to the collaborative efforts of the tyre industry and the Rubber Board," said Mohan Kurian, chairman of Project INROAD.

The project has distributed a record 83m quality planting materials during the five-year period. It has focused on supporting resource-constrained communities in the designated states, particularly small and marginal farmers, most of whom own less than one hectare of land. More than 200,000 beneficiaries have been supported through the initiative, with the project aiming to improve livelihoods and promote socio-economic development.

Project INROAD has also expanded nursery infrastructure across the region. More than 200 nurseries are supplying high-yielding planting materials to growers, while new and improved rubber clones suited to the north-east's agro-climatic conditions are being distributed through the programme.

"With plantations reaching a critical stage, the next component of the project — development of supporting infrastructure such as model smokehouses and dissemination of improved practices among rubber growers — is progressing well under the INROAD Skilling and Production Efficiency Enhancement Drive (iSPEED) initiative," Kurian added.

Under the iSPEED initiative, infrastructure development is intended to improve the quality of rubber produced by farmers through value addition at source. The programme also plans to roll out large-scale digital and in-person training for growers, supported by newly developed training materials that are ready for release.

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