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.

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Flexsys has created what it says is the tyre industry’s first practical and scalable alternative to 6PPD, marking a major step toward replacing a chemical used for decades but now under regulatory pressure.

The company said the new antidegradant is the result of several years of research and testing with federal laboratories, independent scientific groups and tyre makers. Early results show the material could match the performance and safety of 6PPD while avoiding the environmental risks linked to 6PPD-quinone, a transformation product identified in 2020.

Flexsys said the new chemistry provides the short- and long-term protection needed to stop tyres cracking or ageing. It is also designed to fit into existing rubber compounds with minimal changes, which could help manufacturers adopt it quickly. The company added that the product meets environmental and regulatory benchmarks, including criteria set by the Washington State Department of Ecology.

Importantly, the new molecule is not part of the “PPD” family, meaning it does not form quinone during use. Flexsys said this would remove the environmental impact associated with 6PPD-quinone. The company is also using many of the same intermediate chemicals already used in 6PPD production. This could allow manufacturers to rely on existing factory assets and speed the shift to the new technology.

“This achievement reflects our unwavering commitment to responsible innovation, built on decades of expertise in tire protection chemistry,” said Carl Brech, Chief Executive Officer of Flexsys. “Our solution is formulated to deliver the performance and reliability that tire makers expect and is designed for future environmental and regulatory standards.”

6PPD has been essential to tyre durability for 50 years. But studies published in 2020 showed that 6PPD-quinone could harm aquatic species, including coho salmon. Regulators and tyre producers have been looking for a safer option since then. Flexsys said its new antidegradant meets this challenge without reducing tyre safety.

“Our team set out to develop a next-generation antidegradant that meets the tire industry’s highest performance standards without compromising tire safety, while also reducing toxicity,” said Neil Smith, Chief Technology and Sustainability Officer. “I could not be more proud of the perseverance and dedication of the Flexsys R&D team. Our group has been highly motivated by both the technical challenges of this project as well as the positive societal impact that this work will ultimately have.”

Flexsys acknowledged support from the Sustainable Polymers Tech Hub in Akron, Ohio, part of the U.S. EDA Tech Hubs programme.

The company is now working on process optimisation to allow large-scale production. It is also in discussions with regulators around the world to secure approvals for commercial use. Testing with tyre makers is continuing.

“Flexsys is helping set the direction of the tire industry for the coming decades with this development,” Brech said. “We will continue to work tirelessly to bring this breakthrough to the market as soon as possible.”

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Wacker Chemie AG has strengthened its position in China’s fast-growing market for silicone specialities by opening a new application development centre with joint-venture partner SICO Performance Material in the eastern city of Jining.

The 2,300-square-metre facility brings together several laboratories focused on organofunctional silanes, which are used as high-performance additives in plastics, coatings and adhesives. By locating the centre next to SICO’s production and scale-up lines, Wacker aims to shorten development cycles and move new products into the market more quickly. The companies said investment in the site is in the mid-six-figure euro range.

Tom Koini, who leads Wacker’s silicones division, said the opening marks an important step in its China strategy. “As a provider of innovative silicone specialties and solutions, we can use this development center to achieve a key milestone for our business in China. Our focus is on high-margin specialty silanes, for which demand in China is rising continuously. This investment together with our partner SICO strengthens our presence and commitment to the region,” he said.

Wacker, which took a majority stake in SICO in 2022, is seeking to build a larger share of China’s specialty chemicals market, where demand for hybrid polymers has increased for years. These materials help improve the mechanical and chemical properties of adhesives, sealants, coatings and engineered plastics, all of which are used in sectors such as electric mobility, electronics and power equipment.

At the opening ceremony, SICO General Manager Kevin Qu called the centre an investment in the long term. “We can now pool all of our silane expertise here at our application development centre. This know-how ranges from chemical product properties and supply chain matters through to questions of process engineering and current marketing trends. We will leverage this in-depth knowledge to develop forward-looking innovations for our customers. This marks a new chapter of success in the history of our joint venture,” he said.

The companies said the centre will act as a link between research, technical service and manufacturing teams. Scientists will focus on developing additives, adhesion promoters and stabilisers based on organofunctional silanes and functional silicone fluids.

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The Association of Natural Rubber Producing Countries (ANRPC) has released its Monthly NR Statistical Report for October 2025, providing an overview of key developments in the global natural rubber sector.

According to the report, the global natural rubber market in October was characterised by a distinct bearish trend in pricing. This decline can primarily due to a significant surge in production and export activities, which were initially stimulated by the higher prices seen earlier in the year. Meanwhile, overall demand has remained relatively subdued.

Looking ahead to the full year, projections indicate a modest 1.3 percent increase in global production for 2025, a figure that follows a recent downward revision for Indonesia. On the demand side, consumption is anticipated to grow by a slight 0.8 percent, influenced by an upward adjustment to Indonesia's consumption data. Despite the current price pressures, market sentiment shows some mixed signs of improvement, particularly within the tyre trade of certain specific markets.

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DuPont commenced construction on a new MOLYKOTE speciality lubricants production facility in Zhangjiagang, Jiangsu Province, East China, on 18 November 2025 with a groundbreaking ceremony that was attended by Senior DuPont leadership from the MOLYKOTE business and the Asia-Pacific region, alongside government officials and key customers. This strategic investment, situated within the Yangtze River International Chemical Industrial Park, is projected to be fully operational by the beginning of 2027. The initiative is a key component of the brand's global expansion, designed to significantly enhance its responsiveness to regional market needs and foster local innovation.

The new plant will primarily focus on meeting the robust and growing demand for advanced lubricant solutions across several critical sectors in China, including transportation, industrial manufacturing, energy and electronics. By establishing a local manufacturing presence, DuPont aims to create a dynamic platform for collaboration with regional customers. This will enable the company to deliver next-generation lubricants with greater speed, precision and agility, ultimately shortening lead times and strengthening supply chains.

The MOLYKOTE brand, with a legacy spanning over 75 years, is globally recognised for its expertise in solving complex lubrication challenges and improving energy efficiency. Its comprehensive product portfolio, which includes greases, oils, anti-friction coatings and pastes, serves the automotive and industrial maintenance, repair and overhaul markets worldwide. Supported by a global network of manufacturing and research facilities, the brand continues to build on its reputation for performance and reliability.

Eugenio Toccalino, Vice President and General Manager, DuPont MOLYKOTE, said, “Today’s groundbreaking is the beginning of a new chapter in our journey to better serve our customers in China, innovate faster and to be a partner of choice for solving wear and friction challenges across industries. This facility will boost local capabilities for application and new formulation development, empowering customer collaboration and response in real time.”

Yi Zhang, Global VP and Regional President, DuPont Asia Pacific, said, “We are thrilled to be breaking ground on the MOLYKOTE China production facility in Zhangjiagang. This manufacturing unit will enable us to address current needs and future trends for speciality lubricants. It reflects our confidence in the long-term potential of customers in China and Asia-Pacific region and reinforces our commitment to deliver faster, more resilient and locally tailored solutions.”

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