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) released its April 2026 report, highlighting rising prices despite lower production. Output fell 2.59 percent year-on-year due to the seasonal wintering period, dry weather across South and Southeast Asia and El Niño concerns. Brent crude surged to USD 117.29 per barrel, up 13.72 percent from March, driven by Middle East disruptions, which boosted centrifuged latex valuations.

Physical prices rose across all major grades. SMR-20 in Kuala Lumpur increased 4.61 percent to USD 2.13 per kilogramme, while STR-20 in Bangkok climbed 3.53 percent to USD 2.27. RSS-3 in Bangkok jumped 8.10 percent to USD 2.77, and RSS-4 in Kottayam rose 6.53 percent to USD 2.50. Centrifuged latex in Kuala Lumpur gained 12.47 percent to USD 1.93 per kilogramme. Futures markets remained firm, with the Shanghai Futures Exchange September 2026 contract averaging CNY 17,009 per tonne.

For 2026, global production is projected at 15.322 million tonnes, up 2.2 percent, with upward revisions for China and Malaysia. Consumption is forecast to grow 1.3 percent to 15.550 million tonnes, driven by electric vehicle production and recovery in rubber goods. In April alone, estimated output was 772,000 tonnes, while consumption reached 1,235,000 tonnes, a 2.3 percent annual rise.

Trade patterns diverged sharply. China’s imports fell 13.35 percent to 538,200 tonnes due to high inventories, while India’s imports surged 38.79 percent on strong manufacturing demand. Thailand’s exports contracted 4.28 percent to 378,000 tonnes, but Cambodia’s exports soared 106.49 percent. The Malaysian ringgit strengthened to near 3.96 against the US dollar, while the Thai baht stabilised around 3.07 after volatile trading.

The macroeconomic environment remained tense, with US-China trade friction, the Middle East conflict and the US Federal Reserve holding interest rates at 3.50 to 3.75 percent. The near-term outlook for natural rubber is cautiously positive but subject to heightened volatility.

The ANRPC reaffirmed its commitment to objective analysis for the sustainable development of the natural rubber sector. Member governments and stakeholders were encouraged to use the report’s findings for evidence-based policies.

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Indorama Advanced Oxides, a subsidiary of Indorama Corporation, has successfully restarted production at Huelva facility in Spain, achieving its first tonne of Titanium Dioxide (TiO₂) output. The plant, which has an annual capacity of 80,000 tonnes, represents the company’s strategic entry into the global titanium dioxide market. This milestone follows Indorama’s recent completion of the site acquisition from Venator P&A Spain.

The restart marks a crucial step in returning the facility to full operation after the acquisition, ensuring continued supply of the essential white pigment to customers across Europe and global markets. The Huelva team demonstrated strong collaboration and safe execution in resuming activities. This white pigment remains critical for the European paints, coatings and plastics industries.

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Synthos, recognised as Europe’s foremost synthetic rubber producer and a global leader in solution styrene butadiene rubber, has secured the EcoVadis Gold Medal once again. The company, also a top European manufacturer of expanded polystyrene, continues to rank among the world’s most sustainable businesses.

The 2026 assessment placed Synthos in the 97th percentile, with its highest marks received in labour rights, human rights, ethics and environmental stewardship. This achievement underscores steady advancement across multiple sustainability fronts and highlights a sustained dedication to responsible expansion and continuous innovation.

EcoVadis operates as a premier global evaluator of corporate sustainability, judging firms on environmental impact, social responsibility, ethical conduct and supply chain management using international standards. The Gold Medal’s annual renewal demands that Synthos consistently remain within the top three percent of all rated companies worldwide.

This recognition affirms that Synthos’ sustainability measures are both persistent and methodical. The company supports its long-range climate and circular economy goals through participation in the UN Global Compact and reporting aligned with ESRS and GRI standards. Synthos will keep leveraging EcoVadis feedback to refine future priorities and advance its ongoing sustainability journey.

Agata Gładysz-Stańczyk, CEO, Synthos, said, “Receiving the EcoVadis Gold Medal again confirms the importance of sustainability within our strategy and the commitment of Synthos teams across all locations. While we are proud of this achievement, we also see sustainability as a continuous journey. It is embedded in how we innovate, how we operate, and how we create value for our customers, employees, partners and communities. This recognition encourages us to continue strengthening our ambitions and driving further progress.”

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The Rubber Board Statistics Consultative Panel reviewed the performance of India’s natural rubber sector during its 29th meeting at the Rubber Board Headquarters in Kottayam. The panel, which includes representatives from small and large growers, producers’ societies, dealers, processors and tyre manufacturers, examined key indicators such as production, consumption, imports and exports. India remains the sixth-largest natural rubber producer globally.

Indian natural rubber production grew by 3.4 percent in the 2025-26 period, rising to 905,000 tonnes from 875,000 tonnes the previous year. Favourable weather across major rubber-growing regions increased tapping days and productivity. Board initiatives like rain guarding, self-tapping, scientific practices, skill programmes and disease control supported output, while Kerala’s Rubber Production Incentive Scheme also encouraged continued tapping.

Domestic natural rubber prices strengthened, renewing grower interest in tapping. Prices that rose sharply in 2024–25 showed relative stability in 2025–26, narrowing the gap with international rates. The trend continued into early 2026, with RSS-4 peaking at INR 262 per kg on 14 May. Meanwhile, total natural rubber demand rose 1.2 percent, though the auto tyre sector, accounting for nearly 64 percent of consumption, declined by 4.0 percent. The general rubber goods sector posted robust growth instead.

The panel noted a 16.7 percent decline in natural rubber imports, falling to 459,000 tonnes from 551,000 tonnes. However, imports of compounded rubber under HS Code 4005 increased significantly, reaching 349,000 tonnes from 245,000 tonnes in the previous year. Consumption of natural rubber rose 1.2 percent to 1,427,000 tonnes from 1,410,000 tonnes in 2024-25.

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