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.

 

Yokohama Rubber completed enforcement action to halt the production and distribution of counterfeit versions of its “ADVAN Racing” aluminium wheels in China following a coordinated investigation with local authorities.

The Japanese tyre and wheel manufacturer filed an administrative complaint with the Municipal Administration for Market Regulation in Anlu City, Hubei Province, after uncovering a local manufacturer producing unauthorised copies of its high-performance wheels for sports cars.

Authorities in Anlu conducted a raid at the site in November 2024, seizing all counterfeit wheels. A subsequent investigation led to the identification of another company that had commissioned the counterfeit production. Administrative penalties were imposed on the ordering party, including a fine and an order to cease all illegal activity and surrender any remaining fake products.

This marks Yokohama Rubber’s latest successful enforcement action in China. The company had previously filed complaints targeting distributors of counterfeit wheels, resulting in the removal of fake products from the market.

“Yokohama Rubber remains resolute in its stance against the infringement of intellectual property rights, including the production and sale of counterfeit goods, and will strengthen its efforts against such illegal activities in Japan and overseas to ensure that its customers around the world are confident and secure in the knowledge that they are using genuine YOKOHAMA products,” the company said in a statement.

Japanese chemical manufacturer Tosoh Corporation announced plans on Wednesday to construct a second chloroprene rubber production facility at its Nanyo Complex, representing an investment of approximately ¥75 billion (£460 million) to meet rising global demand for the speciality polymer.

The new facility, scheduled to begin construction in spring 2027, will add 22,000 metric tonnes of annual production capacity for Tosoh’s SKYPRENE chloroprene rubber brand. Commercial operations are expected to commence in spring 2030 at the Shunan City site in Yamaguchi Prefecture.

Chloroprene rubber serves as a critical component across multiple industries, from automotive manufacturing to medical applications. The synthetic rubber’s popularity stems from its exceptional resistance to oil, weather conditions, and flame exposure, making it suitable for demanding applications, including automotive hoses, industrial belts, adhesives, and medical gloves.

The expansion comes as global demand for high-performance polymers continues to grow, driven by increasing automotive production and stricter safety requirements across industrial sectors. Medical applications have also seen increased demand following heightened awareness of the requirements for protective equipment.

Tosoh’s decision to double down on chloroprene rubber production reflects the material’s position within what the company terms its “Chemical Chain Business” - a strategy focused on value-added speciality chemicals rather than commodity products.

The investment represents one of the larger capacity expansion projects announced by Japanese chemical companies this year, signalling confidence in long-term demand fundamentals despite current global economic uncertainties.

The Nanyo Complex already houses Tosoh’s existing chloroprene rubber operations alongside other chemical production facilities. The site’s established infrastructure and logistics capabilities influenced the decision to expand at the existing location rather than develop a greenfield facility.

Industry analysts note that the three-year construction timeline reflects the technical complexity of chloroprene rubber production, which requires specialised equipment and stringent safety protocols due to the chemical processes involved.

The expansion aligns with broader trends in the Japanese chemical industry, where companies are increasingly focusing on high-margin speciality products to offset competitive pressures in traditional commodity chemicals from lower-cost Asian producers.

Epsilon Carbon, a leading global manufacturer of carbon black, has launched N134, which it claims is a specialised ‘Hard Grade’ carbon black known for its superior abrasion resistance and durability.

At present, the high-quality N134 grade is being imported due to the lack of consistent quality and supply chain issues in the Indian market. As a result, the tyre makers have to modify their formulations using other grades of carbon black, which it shared often leads to reduced performance.

But now, Epsilon Carbon has become the first company in India to install a dedicated manufacturing unit designed for N134 grade hard carbon. The company is expanding its existing Vijayanagar Carbon complex facility to produce 215,000 tonnes of carbon black.

This will not only ensure consistent supply of N134 carbon black for tyre makers in the country, reduce import dependency, but also open up export potential to markets such as Europe and USA. Epsilon Carbon will also focus on integrate advanced processing techniques to ensure batch consistency for durability and performance.

Vikram Handa, Managing Director, Epsilon Carbon, said, “This is a proud moment for us and for India’s carbon black manufacturing sector as the high quality N134 black will significantly reduce import dependency and provide tire manufacturers in India and abroad with a reliable, high-quality product. Our goal is to match global standards while building India’s capability to serve premium markets.”

Lummus Technology, a leading provider of process technologies and energy solutions, has signed a memorandum of understanding (MoU) with InnoVent Renewables to collaborate on the global licensing and deployment of InnoVent’s continuous tyre pyrolysis technology.

Under the proposed agreement, Lummus will become the exclusive licensor for InnoVent’s proprietary pyrolysis process, which transforms end-of-life tyres into valuable outputs, including pyrolysis oil, gas, recycled carbon black and steel. Additionally, Lummus will offer integrated technology packages that combine InnoVent’s pyrolysis system with its own downstream processing solutions, enhancing the value of fuel and chemical products derived from waste tyres.

InnoVent’s technology provides a fully scalable, end-to-end solution for converting discarded tyres into renewable fuels and high-value petrochemicals, covering everything from pre-processing to purification. The company currently operates a commercial-scale facility in Monterrey, Mexico, with an annual processing capacity of up to one million passenger tyres, and has the capability to expand further.

Leon de Bruyn, President and Chief Executive Officer, Lummus Technology, said, “This is another significant step in expanding and strengthening our portfolio for the circular economy. By combining InnoVent’s tyre recycling technology with Lummus’ global licensing and engineering expertise, we will be addressing the global challenge of waste tyres and creating new pathways for sustainable product development.”

Vibhu Sharma, Chief Executive Officer, InnoVent Renewables, said, “Partnering with Lummus has the potential to accelerate the global deployment of our technology and help us address the environmental and public health challenges of one billion end-of-life tyres that are disposed of annually. Together, we can transform waste into valuable resources, reduce carbon emissions and support the transition to a more sustainable future.”