Elastomer tackifiers are those that produce green tack in elastomers. The term “tack” refers to the ability of two uncured rubber materials to resist separation after bringing them into contact for a short time under relatively high pressure. Building tack of rubber components is an important pre-requisite to enable tyre building on the tyre building drum where different rubber layers are put together on the tyre building drum before they are cured. Another important property of tackifier is, it should retain its tack on storage. A good tackifier, therefore, should have the following properties :

• Very high initial and extreme long-term tackiness
• No adverse effect on the rubber compound cure on scorch
• No interference on (a) rubber to metal bonding (b) rubber to fabric bonding
• Physical properties of the cured rubber remain unchanged
• No effect on the performance of aged rubber compound properties
• Improves rubber compound process reliability
• Show extreme good performance in silica / s-SBR based rubber compound.

In general, NR has enough tack because of the presence of a very high quantity of low molecular weight fraction, having its wide molecular weight distribution. Its low molecular weight fraction also generates during its break down in machines. On the contrary, synthetic rubber lack in tack property because of the absence of enough low molecular weight fraction in them, having narrow molecular weight distribute on (Fig.1). Synthetic rubber also resists in the molecular break down upon mastication and therefore, cannot produce low molecular weight fraction. Resins are typically produced with molecular weights (Mw) between 1,000 and 2,000 with maximum Mw around 3000. The molecular weight is important since tackifying resins work at the surface of the rubber compound and must be able to migrate to the surface to be effective. If the molecular weight is too low, the resin will remain soluble in the elastomer and not migrate its way to the surface. If the molecular weight is too high, the elastomer will be insoluble in the elastomer. Rubber industries use both synthetic and natural resins for tack. Following three types are in major use in the industry :

1. Aromatic Resins (Phenolic, Cumaron Indane)
2. Petroleum based resins
3. Plant Resins ( wood rosin resins,Terpene resins)

Only plant resin is a source of natural resins. However, due to product consistency and different compatibility factors, synthetic resins are in major use. Besides tyre and other rubber applications, the major end-uses for resins are in pressure-sensitive adhesives, hot-melt adhesives, road markings, paints, caulks, and sealants. Manufacturers use hydrocarbon resins to produce hot melt adhesives (for infant and feminine) and packaging applications in addition to glue sticks, tapes, labels and other adhesive applications. All resins are sticky and because of their low molecular weight they migrate (diffuse) easily on the rubber product surface and behaves sticky and that causes tack. Tack property is apparently due to two major reasons :

• Spontaneous diffusion of molecules between two uncured rubber layers.
• Strong molecular forces resulting high degree of crystallinity

Highest level of tack in NR could be due to both the reasons, which means, NR has a high degree of crystallinity (stress induced crystallization) and it has also broad (wider) molecular weight distribution (Fig.1), so that, having plenty of lower molecular fraction can diffuse faster between two layers in contact each other. NR is reported to improve upon its tack on mastication because it generates a higher number of lower molecular weight fraction chains upon breaking down on shearing forces in machines. CR (Neoprene Rubber) shows exceptional adhesive property because it shows the highest degree of crystallinity, even much greater than NR, due to its strong intermolecular attractive force.

Honestly, NR may not require any tackifier because it has enough low molecular weight fraction of chain molecules, due to its wider molecular weight distribution (Fig.1), to be migrated on the rubber component surface and can produce enough tack. It loses its tack mostly because it might have been processed at a higher temperature and is already in the premature vulcanization stage. It can also happen due to the fact that although calendaring or extrusions were done at the right temperature stock was made before adequate cooling and thereby allowed scorching in windup liners. It also loses its tack at cold ambient temperature, in the rainy season and also if the filler level is too high or if the viscosity of the stock is substantially higher than required. However, all synthetic rubber or when synthetic rubber (SBR,BR) is blended with NR, may require to add adequate resins for compound processing.

Except C4,C5 petroleum-based resins, all other types of resins are compatible with NR and is added 1-2 phr. Comparatively C9 petroleum-based resin is better in NR.  Plant-based resins are found to work better in 100% NR. When NR is compounded with synthetic rubber, the tackifier is a must and the dose could be as high as 2-4 phr depending on the content of synthetic rubber, oil and filler in the compound matrix.  All synthetic rubber lag in rubber tack because, in general, synthetic rubber has :

• Narrow molecular weight distribution
• It resisting break down of molecular chains under mechanical shear
• Synthetic rubber is in very pure form

Aromatic Resins (Phenolic, Cumaron Indane) work better in SBR and BR than plant based resins. For hydrocarbon type of elastomers like butyl , halobutyl , EPM and EPDM , petroleum base resin (C4,C5) work better and usually added with 1-2 phr in the formulation, However, with a higher dose of filler, 2-4 phr tackifier could also be added.

Tackifier resins are added to base polymers/elastomers not only  to improve tack (ability to stick) but it also helps in better wetting with filler. Increase in tensile strength by adding resins has been witnessed in different types of elastomers, aromatic resins have been witnessed to increase tensile strength of SBR and its blend.

Effect of Environment on Rubber Tack

The tack of a rubber article is greatly affected by environmental conditions such

as temperature, ozone level and humidity. Environment can not influence tack, however,  if processed rubber compound is used with in 24 hrs. High temperature and humidity conditions have a detrimental effect on the initial tack and tack retention of an elastomer. Phenolic tackifying resins can help improve tack under these conditions, but they have their limits under extreme conditions. Superior tack retention under the influence of high humidity can be often be achieved with epoxy resin modified alkylphenol-formaldehyde polymers.

Hydrocarbon based tackifying resins are sometimes used as a low-cost alternative to phenolic tackifying resins. However, hydrocarbon resins are not as effective at maintaining tack under adverse environmental conditions, like elevated temperature and high humidity, nor do they have the same tack retention. Hydrocarbon resins however, preferred in butyl and EPDM rubber compound due to their compatibility.

Hydrocarbon resins are not as efficient as phenolic tackifying resins, and higher levels are often required to achieve the same tack. High tackifier resin levels can cause a loss in tensile strength, tear strength and, most importantly, hysteresis. In applications where these properties, especially hysteresis, are important, phenolic tackifying resins are excellent choices and should be used.

Perth-based CTS Tyre Recycling is forging ahead with its plans to reshape the options for disposal of end-of-life tyres in Western Australia.

The company, a part of the wider Cometti Group, a family-owned business with more than 40 years of experience in the tyre industry, has invested more than USD 40 million in a state-of-the-art recycling plant at Neerabup, north of Perth, that processes waste tyres into crumb rubber, tyre derived products, reusable high tensile steel wire and reusable textile. The company also made some additions to its management ranks and expanded its links with industry associations as it moves forward with its strategy. These tyres, along with all other sizes, will be remanufactured in the new Neerabup factory into new, high-value goods like load-restraining matting, gym matting, equestrian and farm matting and acoustic underlay.

Leigh Cometti, the company’s Managing Director, identified a potential to diversify into the recycling of end-of-life tyres, concentrating on some of the huge off-the-road tyres utilised in the mining services and agricultural industries. Over 90 percent of the bigger OTR tyres now in use in Western Australia are thought to end up in landfills. Tyres are commonly buried in pits left behind during excavation, which results in the greatest landfill disposals in the Pilbara area. The recycling programmes will lessen the need for more virgin products in addition to decreasing landfill discharge.

Cometti has brought on two seasoned senior level managers to support him as the company grows. Joseph Jeevaraj has joined as Chief Financial Officer, while Darren Rodwell has been named Chief Operating Officer. Both positions work for the Cometti Group, which also owns the Bunbury Trucks Sales and Service dealership, CTS People and Mechanics Recruitment.

Continental and the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH have extended their project to improve sustainability in smallholder natural rubber farming by three years. About 5,000 indigenous smallholders in West Kalimantan, Borneo, Indonesia, have already received training since 2018 on how to grow premium natural rubber in accordance with well-defined sustainability standards. Co-funded by Continental and the German Federal Ministry for Economic Cooperation and Development (BMZ), the initiative aims to engage an additional 1,000 smallholders by 2027.

Lack of knowledge and low farmer income are two major issues in natural rubber farming that are addressed by the Continental and GIZ initiative in the region of Kapuas Hulu, which is home to a UNESCO biosphere reserve. Farmers are taught sustainable agriculture practices and cultivation techniques through the training offered by Continental and GIZ. This enhances the rubber's quality, boosts yield, streamlines the supply chain and raises rubber producers' profits. Additionally, this aids in putting into practice the crucial subject of preserving or reviving biodiversity in the project region. Transparency is also guaranteed across the natural rubber supply chain, from the rubber tree to its usage in Continental's manufacturing, thanks to the implementation of a digital tracking system.

In addition to increasing local capacity, both the companies are actively assisting in enhancing smallholders' quality of life and encouraging environmentally friendly methods of growing natural rubber. The objectives of the EU Regulation on Deforestation-Free Supply Chains (EUDR) are clearly supported by Continental, which has long been actively dedicated to increased supply chain sustainability and transparency. In addition to Continental's tyre facilities, other manufacturers can purchase the sustainably sourced natural rubber produced as part of the project, and more partners are being invited to join.

Dr Michael Radke, Head of Sustainability in Purchasing, Continental, said, “As one of the largest tyre manufacturers in the world, we have a particular responsibility in the natural rubber supply chain. That is why we are committed at all levels and are building capacity locally. Over the past few years, together with GIZ, we have shown that we can make the natural rubber supply chain transparent and at the same time increase farmers’ incomes. Now we want to reach even more smallholders and create the framework conditions for the successes achieved to be sustained.”

The German speciality chemicals company recently inaugurated the first India Application Development Centre (IADC) in the country’s financial capital, reinforcing its commitment and outlook for the country. 

For Lanxess India, tyre industry accounts for almost 25 percent of its business, as against global average of around 10 percent. And the company’s management continues to be upbeat about the growth story for Indian tyre makers.

“India, from our point of view, will play a very important detrimental role (for Lanxess). Because when you want to grow your industry, which Prime Minister Narendra Modi clearly has as an ambition, you need the chemical industry and all their precursors. And if you want to help the Indian industry to further develop (new solutions), you need to have local application for local needs,” remarked Matthias Zachert, Chairman of the Board of Management of Lanxess.

He was speaking on the sidelines of the inauguration of the India Application Development Centre (IADC) in Thane, Mumbai, which also marks a significant commitment by the German chemical major for the country.

Lanxess is said to be the world’s largest supplier of rubber additives focusing on solutions around rubber chemicals, speciality chemicals and processing aids for the rubber industry. The company’s solutions find their way in high-performance rubber products such as tyres, treads, seals and even drive belts.

At present, Lanxess has established two production facilities in India – Jhagadia in Gujarat and Nagda in Madhya Pradesh. The tyre industry is primarily supported by Lanxess Rhein Chemie Additives Divisions, which manufactures Rhenogran and Rhenodiv at the Jhagadia facility. The company has invested over EUR 70 million in the Jhagadia facility, which not only supports the domestic customer base for Lanxess but also its customers in the Asia-Pacific region. The company has a longstanding presence in India, with representation from all 10 of its business units and a workforce of around 800 employees.

It comes as no surprise that Zachert sees India as a critical growth region for Lanxess, offering immense opportunities for collaboration and innovation.

INDIAN TYRE INDUSTRY A KEY GROWTH DRIVER

Globally, the automotive industry in particular is transitioning from being seen as a seller of products to a mobility solutions provider, what’s with new business models or service solutions.

Zachert sees that while the tyre market was consolidated for many years, it has started opening up in the last decade.

“The global tyre market has opened up, strongly driven by Chinese tyre manufacturers but also Indian tyre manufacturers. We have rising stars here in India. Mobility has always led to liberty and flexibility for mankind. This will be a trend that in the next 10-20 years is not going to vanish. Mobility will be important, which means the tyre industry is important. And therefore, I look positively at the tyre industry going forward, notably the one that is located here in India,” said an optimistic Zachert.

It is important to understand that the company has almost 25 percent of its business exposure to the Indian tyre segment, which could be amongst the highest for the company.

“For our group, the mobility exposure that we have worldwide as a company is 10 percent. We are over-proportionally present here in India, which is good and normal because the industry is expanding. The Indian tyre market is expanding not only locally but globally,” he said.

The recent setting up of IADC is part of Lanxess’ strategic focus on India as a key market and innovation hub. The strengthening of R&D will enable the company to enhance its ability to deliver high-value, specialised solutions tailored to local needs.

To begin with, the company has integrated expertise from two key businesses in India: Lubricant Additives (high-performance additives and additive systems, synthetic base fluids and ready-to-use lubricants) and Material Protection Products (antimicrobial, disinfection and preservation solutions). Going forward, the idea is to be present with all business units’ expertise at the IADC.

Namitesh Roy Choudhury, Vice-Chairman and Managing Director, Lanxess India, said, “By establishing the IADC, we are bringing our expertise closer to our Indian customers. This centre will not only support innovation but also strengthen our ability to address evolving market trends with speed and precision.”

For Lanxess India, the IADC aligns with its transformation journey towards a speciality chemicals company. The aim is to focus less on cyclical business areas and solutions for critical applications and move towards a partner for sustainable mobility or consumer protection. And the company sees India’s growing industrial base and expanding consumer markets as an ideal platform for driving such advancements.

SUPPORTING THE TYRE INDUSTRY

The production of the plain looking black tyre is more than just moulding of rubber; it is a complex process, which includes incorporating various raw materials and scientific steps to ensure that the tyres are built up to a particular specification. After all, tyres remain and are supposed to be the sole point of contact between a vehicle and the road when in motion.

Lanxess, for its part, supplies solutions across mixing, batch-off, extrusion & tread marking, tyre inspection & repair, tyre curing, green tyre spraying and tyre building processes.

According to the company, a durable car tyre is the result of a complex manufacturing process in which the tyre is built-up from various rubber compounds and reinforcing materials. It explains that by using rubber chemicals and various fillers, the raw material rubber is turned into a high-performance product. This is because rubber is soft and not very durable until vulcanisation. By selecting the type of rubber, the crosslinking chemicals and additives required for the desired technical properties of the end-product, high-performance products such as tyres and other rubber products are created.

EUROPEAN COMPANIES TO STEP OUT OF PETROCHEMICALS

The chemicals industry has undergone a sea of change, especially given the evolving trend from geography-focused development to globalisation. For the last few years, there has been a growing pressure, especially given the focus on sustainability.

To support the sustainability drive, the company recently introduced Vulkanox HS Scopeblue, a next-generation rubber additive designed to help tyre manufacturers produce more durable and environmentally friendly tyres. The anti–degradant effectively protects tyres from the damaging effects of oxygen and heat while offering reduced environmental impact. Its low volatility and minimal migration tendency further enhance tyre performance and longevity, making it an optimal solution for modern, eco-conscious manufacturing.

The company claims that the Vulkanox HS Scopeblue boasts a carbon footprint more than 30 percent lower than its conventionally produced counterpart thanks to the use of bio-circular acetone and renewable energy in its production process. It is being currently manufactured at an ISCC PLUS-certified plant in Germany; this mass-balanced additive retains the same chemical structure as the original product, allowing tyre manufacturers to adopt it seamlessly without altering their existing production processes.

Zachert further said, “Times lead to change. The industry dynamics of chemicals has been adjusting to change for the last decade and will continue to see changes for the next decades. If I look into the next 10 years of the chemical industry, my personal prognosis is that you will see that the European chemical companies will more and more step out of petrochemicals and go upstream. And this is happening as we speak. My thesis also is that the European industry will focus more on niche polymers and speciality chemicals. The upstream and volume polymers will go elsewhere, where you have the raw materials and cheap energy. Countries that are destined to dominate these kinds of chemicals over the next 10 years, is the Middle East and the United States. Europe used to be the epicentre of chemicals 20-30 years ago from polymers to chemicals to pharmaceuticals.”

Then there is the shift from global supply chain to more of regional supply chain given the geopolitical situation.

“I see that with the current world with geopolitical tensions, the likelihood is high that we will go back to trade zones. And therefore, the global value chain in chemicals is one where many companies will have to rethink the global approach and turn towards a more regional approach,” added Zachert.

Japanese speciality chemicals manufacturer Zeon Corporation and US-based biotechnology firm Visolis Inc. announced plans to begin preparatory steps towards constructing a commercial-scale production facility for bio-based isoprene and sustainable aviation fuel (SAF).

The companies are evaluating multiple potential sites for the new facility, which will use Visolis’ proprietary fermentation and downstream processing technology. The announcement follows a successful joint feasibility study that confirmed the platform’s competitive advantage for commercial-scale production.

“Visolis has proven to be a valuable innovation partner, and we are excited to take this important next step together,” said Tetsuya TOYOSHIMA, President and CEO of Zeon. “Bio‐based isoprene and SAF are key to our long‐term vision for sustainable growth, and this project reflects our commitment to delivering impactful technologies in collaboration with leading startups."

According to the companies, the next phase of planning activities will include detailed engineering, site assessment, permitting, and stakeholder engagement.

The initiative forms part of Zeon’s broader sustainability objectives and decarbonisation strategy while advancing Visolis’ mission to commercialise its technology.

The two companies have collaborated for several years to develop and scale next-generation, bio-based materials.

Industry analysts note that bio-based alternatives for chemical production and aviation fuel have gained significant attention as companies across various sectors seek to reduce their carbon footprint.

Both companies indicated that further updates will be provided as the project advances.