In the 1930s, when rubber became one of the essential commodities, selection was never a problem because we had only Natural Rubber (NR) that time. Today, beyond 2010, there are number of elastomers are being used in the industry and the choice is typically important with respect to the competitive advantage of both, durability in the service and cost.

 

NR was called rubber because it could have rubbed out pencil mark. When other synthetic rubbers were produced, they had also similar property of rubbing out pencil mark, but were called elastomers because NR was then typically identified as Rubber. However, both NR and other synthetic rubber (SR) together are called elastomers, because they had typical elastic properties and interestingly, all rubber and elastomers are high polymers. From the time 1930 , industries have increased many folds of time. Engineering requirement in the manufacturing industries, with respect to temperature, pressure and durability have also simultaneously increased and our demand on the applications have also been increased.

CAPTION Fig.1: Asia Pacific Total Elastomers (54%), NR+SR

 

With very competitive demand in the market, all rubber properties cannot be achieved only by NR. Balancing critical demand for rubber applications, that we require in our day to day life, use of SR or blending with SR has become very common practice in the industry today.

 

For example, other than pneumatic tyre, there is hardly any uses of NR these days in automotive industries. Uses of various grades of EPDM, Silicone rubber (Q), Nitrile rubber(NBR), Fluoro Elastomers (FKM) , Perfluoro Elastomers (FFKM) , Hydrogeneted Nitrile rubber (HNBR), Chlorosulphonated Polyethylen (CSM), Polychloroprene(CR) , Polyurethane Rubber (AU/EU), Fluorosilicone Silicone Rubber (FQ) etc. have been increased due to typical automotive parts requirement. Since automobile spares are now mostly manufactured in Asia Pacific countries, they are the largest consumer of total elastomers (Fig.1).

 

CAPTION Fig.2: Only SBR is the highest (47%) synthetic rubber

 

After NR, the next high consuming elastomer is SBR (Fig.2) because of its higher filler and oil loading capability and higher abrasion resistant quality. After SBR, the next high quantity rubber used is BR, followed by IIR (BIIR,CIIR) and EPDM. Recently silicone rubber uses have increased many fold times in Western countries, China, Japan, Korea and in India. However, the total SR uses remains highest in Asia Pacific(Fig.3).

 

CAPTION Fig.3: Asia Pacific Highest Consumer of SR (48%)

 

In critical applications, it is therefore, advisable to give considerable thought, or take advice, on the formulation of the compound. As the potential for 'tailoring' compound to specific applications is essentially limitless, it is often advisable to carry out preliminary qualification tests to ensure that the compound chosen will perform as intended by customer need.

A considerable thought in critical applications, for the formulation of the specific compound need considerable experience with selecting raw materials and art of processing. Very common mistakes by rubber compounder is mostly related to incorrect selection of (1) ingredients, (2) their doses, (3) rubber blends and (4) correct machines. Rubber compounding is an art of developing rubber mixtures with suitable raw material and their doses, that will perform in desired services but with minimum cost possible such that product can be competitive in the market and can be processed well in machines without any difficulties faced by man and machines.

 

There are broadly two classes of Rubbers or elastomers, they are Natural Rubber (NR) and Synthetic Rubber (SR). NR occurs naturally in the plant and hence the name but all synthetic rubbers are man made rubbers and are produced by chemical synthesis. Among the Synthetic elastomers, there is again two category; one is general purpose rubbers (GPR),which can be used as equivalent to NR, e.g., Butadiene Rubber (PBR) and Styrene Butadiene Rubber (SBR) and the other category is specialty elastomers. Specialty elastomers are generally costlier than GPR and are only used in special purpose. Following are the list of specialty elastomers ,which are widely being used in rubber industry beyond 2000:

 

Butyl Rubber (IIR), Chlorobutyl Rubber (CIIR), Bromobutyl Rubber (BIIR), Chlorinated Polyethylene(CM), Chlorosulphonated Polyethylen (CSM), Ethylene Acrylic(EEA) , Ethylene Propylene Rubber(EPM) , Ethylene Propylene Diene Rubber(EPDM), Fluoro elastomers (FKM), Hydrogenated Nitrile Rubber (HNBR), Isoprene Rubber (IR), Nitrile Rubber(NBR) ,  Polyacrylic Rubber (ACM), Perfluoro Elastomers (FFKM), Polychloroprene (CR) , Polysulphide Rubber (TR) , Polyolefin Elastomer (POE),   Polyurethane Rubber (AU/EU) , Silicone Rubber(Q), Fluorosilicone   Silicone Rubber (FQ) etc.

 

Elastomers having carbon-carbon double bond on the elastomeric backbone could be cross-linked with sulphur and accelerators. Many of these elastomers are also could be cured with organic peroxides, examples are NR,SBR,BR, AU/EU, CM, CR,CSM,EPM,EPDM,FPM,NBR,HNBR,IR,POE,Q,FQ. Elastomers that cannot be cured with organic peroxides are; ACM,IIR,CIIR,BIIR,ECO.

 

Rubber compounding

 

Rubber compounding is an art of developing rubber mixtures with suitable raw material and their doses, that will perform in desired services but with minimum cost possible such that product can be competitive in the market and can be processed well in machines without any difficulties faced by man and machines. In all rubber industry today, the biggest challenge is cost reduction of a good quality product. During selecting raw materials, therefore, the cost of these will also play a vital role in compound designing.

 

A rubber product might require desired physical properties and ageing properties. For this one need to add particular reinforcing filler or a suitable combination of reinforcing fillers to have desired physical properties. The typical ageing resistant property may be achieved with only NR by adding suitable anti-degradants or, NR could also be blended with synthetic elastomers with better ageing resistant property. NR being cheaper and easily available it is the first choice having good strength, abrasion , tear strength and low heat development in dynamic condition. A synthetic rubber product might require good green strength , in that case either NR or blend of rubber is the choice. For example, for better green strength of CIIR, it is often blended with NR.

 

CAPTION Fig.4: Turn-up Bladders

 

A rubber product may require a specific need , say air retention property or oil resistance property. For the former case the choice is essentially butyl rubber (or, halobutyl rubber , CIIR,BIIR) and for the later it is usually, NBR/HNBR and for both oil resistance and air impermeability, the usual choice is NBR / HNBR rubber (Turn-up bladder for tyre building operation, Fig.4). For a typical product, if the property demands oil resistance at 200 ⁰C, then the choice is FKM (Fluoroelastomers) or Q. For resistance upto 328 ⁰C , it is FFKM.

CAPTION Fig.5: Typical Industrial Gaskets

 

Heat resistance property is typically related to product durability and sustainability at desired temperature and is very important for various industrial gaskets (Fig.5). For temperature resistant rubber compounding and following temperature resistance of the polymer is important, NR ~ 65 °C, SBR ~ 75 °C, NBR ~ 110 °C, HNBR ~ 180 °C, Q ~ 200 °C+, FKM ~ 240 °C, FFKM ~ 328 °C. The temperature ranges quoted are only a rough guide, because the temperature resistant property also depend on the typical compound design as well, depends upon the particular application, and may depend on detailed differences between alternative versions of the same rubber.

 

Rubber compound is always developed as per customer need. For any rubber article, the first choice is the selection of right rubber. Rubber is selected mostly on the basis of :

 

• Cost
• Heat and/or Oil Resistance
• Temperature Requirements
• Energy Absorption
• Seal Ability
• Flex Resistance
• Water Resistance
• Gas Impermeability
• Electrical Properties
• Abrasion Resistances
• Dynamic Properties
• Flame Resistance

 

Rubber compound related definitions

 

• Elastomer, a polymeric material that recovers substantially to its original shape after significant deformation at room temperature.
• Compound, a mixture of elastomer and other materials that is intended to process (mold) satisfactorily and meet end-use specifications.
• Filler, a particulate material added to an elastomer that modifies both the workability and the end-use behavior of the resulting composition.
• Plasticizer, a material added to an elastomer to improve its workability.
• Resins are added to improve rubber tack.
• Waxes also used as plasticizer , are also added for smooth finish of rubber articles.
• Antioxidant, a chemical added to a compound to slow or prevent oxygen attack on the compound.
• Antiozonant, a chemical added to a compound to prevent ozone attack.
• Cross linking agent, a chemical added to a compound to link the long molecules in a polymer together, or to assist in the cross-linking process.
• Accelerator, a chemical added to a compound to increase the rate of cross-linking in the compound.
• For example, sulfur links the long molecules, while an accelerator increases the cross-linking rate.
• Retarder, a material added to an elastomer compound to delay the onset of cross linking (scorch).
• Vulcanization is same as cross-linking but with sulphur.
• Peroxide also helps in cross-linking process.

 

 

Elastomer blends

 

Elastomer blends often creates problem when two different types of unsaturated rubbers are mixed and vulcanized together. For example, NR and IIR have two different unsaturation level and hence both sulphur , ZnO and black flows more towards polar rubber, on NR phase, and results undercure in IIR phase and the resultant blend vulcanizate becomes spongy and cannot be used.

 

GPR (NR,SBR,BR) rubber could be blended to any proportion. For higher synthetic rubber level (BR,SBR) , accelerators dose is often adjusted to higher side and sulpur level is adjusted to lower side, because for equivalent curing, BR, SBR requires more accelerators as compared to NR. Stearic acid is added 2-3 phr with only synthetic elastomer and for NR, stearic acid dose of 0.5 phr is enough.

 

CAPTION Fig.6 : Micro Dispersion of Rubber Blends

 

Practically most of the polymers are not miscible to 100%, polymer blends usually consist of micro-dispersion of one rubber into the other rubber and this results after intensive mixing of these two different polymers. These micro dispersed rubber often has dimensions around 0.1-1.5 nm(Fig.6). When fillers are also mixed into such blends, a situation may develop in which the filler unevenly distributed between two phases. Such uneven distribution of fillers, naturally effects the uniformity of compound physical properties. In most blends the effect on the properties of blended elastomers depend on:

 

1. The polymer compatibility
2.  Distribution of fillers in different phases and
3. The degree of cross-links between rubber phases

 

Though NR,SBR,BR could be blended to any proportion , yet the blended phases are not compatible to hundred percent and there is also phase separation, where, on proper identification one can witness that there is phase separation with NR & SBR, NR & BR, BR & SBR. However, upon proper mixing these phase differences could be minimized (Fig.7) such that the resultant blend gets cured almost homogeneously . That is why very highly dispersed NR (5 to 10 parts) could also be co-cured with IIR.

 

 

CAPTION Fig.7 : Well Dispersed Rubber Blends

 

 IIR cannot be blended with GPR but can be blended with EPDM (having ENB diene content between 2-3 mole%) to any proportion. Higher diene content EPDM rubber (ENB, >9.0% mole) could be well blended with GPR. If high diene content EPDM is blended with IIR, filler, sulphur, accelerator and zinc oxide flows more towards EPDM than IIR. IIR could be blended with CIIR and BIIR to any proportion. Such blend is often used in making tyre inner-tubes and hose jacket compounds. When CIIR and BIIR doses are on the higher side with IIR (>60phr) it is worthwhile that zinc oxide is added in the final batch since zinc oxide is curative for CIIR & BIIR.

 

Besides zinc oxides, CIIR and BIIR can also be cured with sulphur/accelerator system as well. However, for very good heat resistant property, they are often cured with ZnO. Highly dispersed plastic (LDPE) could also be blended with CIIR/BIIR with no detrimental effect but with improvement on air permeability.

 

CIIR and BIIR could be blended to any proportion with GPR. Such blend is often used in tyre inner liner. When CIIR and BIIR doses are on the higher side (>60phr) both zinc oxide and amine type anioxidant/antioxonates are added in final batches as these are curatives in CIIR and BIIR.CIIR blend with GPR and EPDM is used in PC sidewall for glossy finish sidewall and addition of CIIR also help to reduce the curing time of PC tyre. Blend of EPDM/NR/SBR and EPDM/NR/SBR/CIIR are often used in tyre side wall compound for better look.

 

CR rubber is not normally blended in the industry as it is mostly used in adhesive industry. However, they can be blended to any proportion with GPR. In adhesive industry crystallinity is important and CR gives the highest degree of crystallinity among all general-purpose rubber. CR could be blended with IIR , close to 5-15 phr, for bladder making and in general, only 5.0 phr is added in the beginning of the mixing cycle.

 

In bladder mixing, Zinc oxide could be mixed with CR in master batch. CR is premasticated in mixing mill for making bladder compound, before adding in Banbury.CR/BR blend is used in hose covers.CR could also be blended with GPR at any proportion like CIIR. Both zinc oxide and amine type antioxidant / antioxonates are added in final batches as these are curatives in CR and CIIR.

 

In general Silicone rubber (MQ,PMQ,VMQ) cannot be blended with any other rubber because of phase difference problem but highly dispersed EPDM could be blended with it upto 10 -15 phr. EPDM/Q blend is used in heat resistant cover roll compound.

 

EPDM, being a good elastomer as weather resistant and heat resistant is often blended with number of other elastomers to get the benefit of the vulcanisates.

EPDM/CR blend are very popular in making gaskets. EPDM/IR blend is widely used in car wiper rubber blades. EPDM/SBR blends are used in gaskets, sponges and hose stocks. EPDM/CSM blend is used in transmission belt, conveyor belt and in hose covers. EPDM/LDPE blend is very popular in making cable insulation compound.

 

NBR in general, is not blended with other elastomers as this rubber having higher degree of polarity , is exclusively used for oil resistance property. It may have acrylonitrile content ( ACN) ranging from 18-50%. Incase of higher oil resistance, the elastomeric grade is selected with higher ACN. For better abrasion however, 10-20 phr of BR could be added to NBR with the aid of good dispersing agents , used in shoe sole, high abrasion resistance rolls and in conveyer belts. Higher ACN content will have better abrasion property. NBR could be cured both by sulphur/accelerators or by peroxides. Hydrgenated NBR (HNBR) has emerged into market with better heat resistant property as compared to NBR. For intermediate heat resistant property NBR and HNBR could be blended.

 

NBR/SBR blends used in hydraulic hose tubes, high pressure hose, belt cover, idler roll compounds and in gasket compounds. NBR/PVC blend and NBR/PVC/BR blend are used for roll cover compound, very popular in electric cable insulation and in closed cell sponge applications in shoe industry. XNBR/PVC blend is used for heavy duty cable jackets, roller cover, belt cover, hose cover stocks etc. NBR/IR blend and NBR/TR blend is popular in colored or non-black roll covers. The later is mostly used in printing roll cover compound.

Birla Carbon has confirmed a price increase of up to 15 percent for its Speciality Materials products across Asia, scheduled to take effect on 1 October 2026. The company pointed to significant and sustained rises in feedstock costs, driven partly by ongoing geopolitical instability and disruptions in global feedstock markets, as the reason behind the adjustment.

Although Birla Carbon pursued operational efficiencies, supply chain optimisation and disciplined cost management to soften the impact, the scale and persistence of the cost escalation left a price adjustment unavoidable. The company's sales teams will engage customers directly to explain the details and help them navigate the transition.

ACE Laboratories, an independent ISO/IEC 17025-accredited polymer testing laboratory, has partnered with Abdallah Consulting, LLC, a prominent tyre pyrolysis advisory firm, to introduce VericarbSM. This independent certification programme verifies that materials marketed as recovered carbon black (rCB) meet established criteria for rCB.

Recovered carbon black, derived from end-of-life tyres via pyrolysis, serves as a sustainable substitute for virgin carbon black in rubber and polymer applications. However, the emerging market has lacked the standardisation and independent verification that established supply chains provide. VericarbSM addresses this gap through independent material characterisation and rubber performance data, offering stakeholders a consistent basis for evaluating rCB products.

For producers, certification accelerates market entry and improves buyer approval rates. Consumers gain more capable suppliers and reduced evaluation time, while investors benefit from clearer volume sizing and fewer costly test failures. The programme is jointly administered by both organisations.

Erick Sharp, CEO, ACE Laboratories, said, “The rCB market has enormous potential, but growth has been held back by uncertainty about material quality and consistency. VericarbSM gives producers a way to prove their product and gives buyers the independent data they need to say yes.”

Dave Abdallah, Founder, Abdallah Consulting, said, “One key reason for the delayed growth of recovered carbon black is lack of product performance information in the customer’s language. ASTM standards are critical; in fact, most testing done in the process follows ASTM methods. But customers relate to a product better when its performance is shown in applications relevant to them. VericarbSM solves the language issue by showing verified rCB in terms of rubber performance while simultaneously adding credibility via third-party analysis and reporting.”

Zeon Corporation established Zeon Chemicals Kurashiki Co., Ltd. on 23 July 2026 to take over the acrylic rubber operations of fellow group firm Tohpe Corporation. The new entity, headquartered in Kurashiki City, Okayama Prefecture, is wholly owned by Zeon with paid-in capital of JPY 10 million and is led by representative Koji Minami.

On 21 August, Tohpe and the new subsidiary signed an absorption-type company split agreement, prompting Zeon to begin the procedures required under the Companies Act. Operations at the new company, focused on manufacturing and selling acrylic rubber and related activities, are scheduled to commence on 30 October 2026.

Acrylic rubber, known for its heat resistance, is used in automotive components including oil seals and hoses. The Zeon Group already maintains four production sites across Japan, United States and Thailand, forming a global supply network for the material.

The restructuring follows Zeon’s 11 May 2026 announcement that it would transfer Tohpe shares to NATOCO Co., Ltd. of Miyoshi City, Aichi Prefecture, as part of Tohpe’s paints business divestiture. Tohpe’s acrylic rubber operations, which complement Zeon’s Elastomers Business, will now be positioned as a key specialty rubber manufacturing site, with closer operational coordination intended to strengthen Group competitiveness and corporate value.

The company is betting that a polymer manufactured from end-of-life truck tyres can disrupt the market for petroleum-based styrene-butadiene-styrene (SBS), a widely used road-binding additive whose pricing and availability are tied to global oil markets. After completing a live road trial with Road Science and Auckland Transport in New Zealand, the company is preparing to use the results as a springboard for expansion into Australia and Sub-Saharan Africa, positioning the recycled material as a lower-cost, lower-carbon alternative to virgin polymers.

New Zealand-based Revyre Global Limited is positioning a polymer manufactured from end-of-life truck tyres as a lower-cost alternative to petroleum-based styrene-butadiene-styrene (SBS) after completing a live road trial with Road Science and Auckland Transport in New Zealand.

The company has spent several years developing the product as a direct replacement for SBS. Unlike conventional tyre-derived asphalt, which relies on crumb rubber, the company’s Chief Executive Officer Shaun Zukor told Tyre Trends that its proprietary thermomechanical process produces a remanufactured polymer with blending characteristics similar to SBS, allowing it to be used in existing asphalt infrastructure.

“Our primary objective was to develop a drop-in replacement for SBS, which is a petroleum-derived synthetic polymer,” Zukor said. “SBS is expensive, made from virgin materials and is widely used to improve road durability, fatigue resistance and overall pavement performance.”

The company began engaging Road Science, a division of Downer, and Auckland Transport after completing laboratory validation with engineering consultancy WSP in New Zealand.

Before approaching customers, it invested around 18 months in laboratory testing to validate the material’s performance.

Following successful laboratory trials, Road Science carried out its own evaluations before, together with Auckland Transport, deciding to trial the material on Blockhouse Bay Road, one of Auckland’s busiest roads.

The project then underwent another lengthy approval process involving Auckland Council and scientific advisers.

“It took another year to a year and a half to obtain all the necessary approvals from the council and its scientific advisors,” Zukor said. “They wanted to verify that all the claims in our technical literature were accurate.”

Construction of the trial road took place over three days in March and the company expects to receive the first performance data around September. Those results are expected to support commercialisation in overseas markets.

“Our business is focused only on New Zealand at the moment because we’re using it as a proof of concept,” Zukor said. “Once those results are available, we’ll publish them. That will place us in a much stronger position to take the product into Australia and Sub-Saharan Africa.”

The company estimates that entering Australia would take another 12 to 18 months after trial results are available and a planned New Zealand manufacturing facility becomes operational.

Although the current road project used only a small quantity of material because it is a demonstration, Zukor said the commercial opportunity could expand significantly.

“We used a relatively small amount of material for this particular project, but if the opportunity grows as expected, supplying the Auckland Transport network alone could eventually consume between 40–50 percent of our production capacity,” he noted.

MATERIAL ECONOMICS

The company currently manufactures the material primarily from truck and bus radial (TBR) tyres and earthmover tyres because of the higher natural rubber content.

While the SBS substitute represents the company’s immediate focus, it has divided its broader product portfolio into three categories. Revpol A, manufactured mainly from passenger and light truck tyres is intended for lower-performance rubber products such as rubber tiles, shoe soles and conveyor belts.

Revpol B targets asphalt applications and new tyre manufacturing, while Revpol C, produced largely from earthmover tyres, is designed for higher-performance applications.

The company is not currently manufacturing at its own facility but plans a new production unit in New Zealand. Until that facility is operational, product for trials is being supplied by its Canadian partner.

The technology relies primarily on a thermomechanical recycling process rather than chemical recycling. Whole tyres are broken down with steel separated from the rubber before the rubber is processed to a 30-mesh particle size and passed through Revyre’s proprietary thermomechanical process.

Zukor said only a very small amount of non-toxic, FDA-approved chemicals are used and that the process is driven primarily by operating parameters rather than chemical reactions.

He added that one of the key advantages of the technology is that it can be incorporated into existing SBS blending infrastructure with minimal changes as most development work focused on determining the optimum blending ratio rather than overcoming technical limitations.

“The primary technical challenges relate to the blending ratio,” he said, adding, “The higher the percentage of Revpol you add, the higher the temperatures and shear forces required in the bitumen blending terminals.”

Although the company has successfully blended as much as 20 percent Revpol into bitumen during development, Zukor said performance gains diminish beyond a certain point.

It has identified an optimum blend of between 5 percent and 10 percent depending on the application, ranging from conventional roads to heavy-duty pavements and airport runways.

“Any facility that currently blends SBS using its existing infrastructure can also blend our product using that same infrastructure,” he said.

CATALYST FOR SAVINGS

Zukor believes the material can reduce both costs and environmental impacts while improving pavement performance.

“We want to create a product that is environmentally sustainable, has an abundant raw material supply and is 20–40 percent cheaper than virgin materials while also having a significantly lower carbon footprint,” he stated.

Laboratory testing has produced encouraging results. According to Zukor, New Zealand’s wheel-tracking standard requires materials to withstand 800,000 load cycles, while Revyre’s product continued to perform until testing was halted at two million cycles.

“Our product achieved nearly two to three times the required wheel-tracking performance compared with standard bitumen,” he noted.

He also added that the objective is to produce road surfaces that are less expensive, more durable and environmentally sustainable while simultaneously addressing the challenge of managing end-of-life tyres.

“We believe this product ticks all of those boxes and have obtained a patent for it,” he said.

MANUFACTURING SCALABILITY

Although the company is currently relying on manufacturing capacity in Canada, Zukor said its modular production model could support significant expansion once commercial demand develops.

“We can currently produce up to 10,000 tonnes of this product, but because our production facilities are modular, capacity can easily be scaled anywhere from 1,000 tonnes to 50,000 tonnes, depending on market demand and the requirements of a particular region,” said Zukor.

Once the planned New Zealand facility becomes operational, Zukor expects its tyre feedstock to be supplied through Tirewise, the country’s extended producer responsibility (EPR) scheme for end-of-life tyres.

Under the programme, every imported tyre attracts a levy that funds incentives for registered collectors, processors and end users to move tyres through the approved recycling chain. Zukor said Revyre intends to register again as a processor after commissioning its new plant.

GOING PAST HURDLES

Zukor acknowledged that customer adoption remains the biggest hurdle. Road contractors also need to validate new formulations through laboratory testing before incorporating them into their pavement designs. Hence, Revyre is focusing on multinational contractors already operating in New Zealand to accelerate adoption, believing successful validation locally could support deployment elsewhere within those organisations.

He also believes global dependence on petroleum-derived SBS strengthens the case for tyre-derived alternatives.

“If you look at SBS, it’s already a product that’s in very high demand globally. Because it’s petroleum-based, its availability and pricing are heavily influenced by global macro-economic and geopolitical events,” Zukor said.

He said the company’s commercial proposition rests on three principles viz-a-viz consistent quality, supply and pricing.

According to Zukor, replacing virgin SBS with tyre-derived polymers could help localise supply chains, reduce exposure to petroleum price volatility and improve environmental outcomes while lowering costs for road owners.

Beyond New Zealand, Revyre is also evaluating opportunities in North America through its Canadian partner and is exploring future markets for tyre-derived materials.