In tire manufacturing, vulcanization activators play a crucial role in transforming raw rubber compounds into durable final products. Traditional zinc oxide-based systems, typically used at 3-5 parts per hundred rubber (phr), face increasing environmental scrutiny while still needing to maintain precise control over cure kinetics, crosslink density, and final mechanical properties.

The fundamental challenge lies in developing activator systems that can reduce zinc content while maintaining or improving vulcanization efficiency and the resulting tire performance characteristics.

This page brings together solutions from recent research—including vulcanization-activating fillers with bound zinc, aminoacidic-activated carbon black systems, and novel silane compounds with multiple functional groups. These and other approaches demonstrate practical pathways to optimize vulcanization chemistry while addressing environmental and performance requirements in modern tire manufacturing.

1. A novel zinc complex for rubber vulcanization: Enhanced mechanical properties and reduced environmental impact through <scp>ZnO</scp> substitution

mitra tavakoli, parisa peyzari, fatemeh tamaddon - Wiley, 2025

Abstract Decreasing zinc consumption in vulcanization processes of rubber represents a major environmental issue for the industry. To overcome this problem, novel method has been developed based on replacing conventional oxide (ZnO) with dodecyl sulfate (Zn(DS) 2 ) styrene‐butadiene (SBR). The amount free incorporated composites quantified by flame atomic absorption spectroscopy (FAAS). Results indicated reduction content samples containing Zn(DS) 34%–77% as compared control sample 3 phr ZnO. Further investigations have also performed to find out effect crosslink density, thermal and mechanical properties, curing characteristics, dynamic behavior swelling tests, rheometric measurements, tensile thermogravimetric analysis (TGA), (DMA). Replacement ZnO increased density significantly, much 105%, thus providing evidence enhanced availability Zn cations accelerator. Also, increases strength ice grip rolling resistance 30%, 101%, 13%, respectively were observed. Overall, shows promise viable alternative traditional ZnO‐based activators tire industry increasing performance decreasing... Read More

2. Rubber Composition with Organic Sulfur Compound and Benzothiazole Derivative for Rapid Crosslinking

SUMITOMO RUBBER INDUSTRIES LTD, 2025

Rubber composition containing an organic sulfur compound that cures quickly and forms good crosslinking. The composition includes a base rubber, co-crosslinking agent, crosslinking initiator, benzothiazole derivative, and organic sulfur compound. The benzothiazole derivative, which can be a compound represented by formula (1) or (2), and the organic sulfur compound have a mass ratio of 0.5 to 10. This composition allows shorter crosslinking times compared to conventional sulfur vulcanization.

3. Self-Healing Performance of Vulcanized Natural Rubber Using MgO/ZnO as a Binary Activator

- Iran University of Science and Technology, 2025

Self-healing vulcanized natural rubber (V-NR) was prepared with MgO/ZnO as a binary activator system in the study. Standard Vietnam Rubber Grade 3L (SVR3L) used NR source. The SVR3L ZnO, MgO/ZnO, or MgO activators and other vulcanizing reagents. total amount of 5 parts per hundred (phr), which mass ratio to ZnO 3:2. Furthermore, sulfur content either 1.0 1.5 phr. self-healing experiment performed at 25, 50, 100 °C for 12 hours 24 hours. cure characteristics compounds were analyzed determine optimal vulcanization time (t90) maximum torque (MH). Raman spectroscopy evaluate relative disulfide polysulfide bonds. Self-healability assessed by determining stress strain break V-NR before after process. result showed that t90 value sample using reduced 50% compared ZnO. phr had best ability among all samples, tensile strength recovery 35% elongation 113% original sample. attributed bonds rather than predominantly formed samples an activator, according spectroscopy.

4. Process for Coating Textile Reinforcement Yarns with Polyisocyanate-Based Bath for Composite Material Formation

CONTINENTAL REIFEN DEUTSCHLAND GMBH, 2025

Process to make composite materials for elastomeric products like tires with improved sustainability and adhesion. The process involves activating textile reinforcement yarns with a bath containing polyisocyanates, waxes, and surfactants before immersing them in the rubber mixture. This coating improves adhesion between the yarns and surrounding rubber. The coated yarns are then used to create the composite material. The activation bath can be made from recycled materials like post-consumer PET bottles. The composite with recycled yarns provides similar performance to conventional composites but with lower environmental impact. The vulcanized composite material and resulting elastomeric products, like tires, have improved sustainability and adhesion compared to conventional composites.

US2025115018A1-patent-drawing

5. Micronized Rubber Powder with Silane and Silica Activation for Enhanced Vulcanization and Dispersion

ATLANTIS RUBBER POWDERS BV, 2025

Upgrading micronized rubber powder (MRP) for large-scale reuse in tires by chemically activating the powder to improve performance. The activation involves treating the powder with silane during grinding to prevent sticking and using silica as a dusting agent. This functionalizes the powder surface to enhance vulcanization and dispersion in rubber compounds. The activation step involves contacting the powder with silane, silica, peroxides, or other activators. This allows using lower amounts of MRP in tire formulations compared to unactivated powder, which improves properties like tear strength, abrasion resistance, and dynamic performance.

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6. Rubber Composition with Sulfenamide, Dithiocarbamate, and Thiazole/Thiuram Polysulfide Accelerators

THE GOODYEAR TIRE & RUBBER CO, 2025

Rubber composition for high mileage truck tires with improved wear resistance and aging properties. The composition contains a specific combination of curing accelerators - sulfenamide, dithiocarbamate, and thiazole/thiuram polysulfide accelerators - along with natural rubber, polydiene rubber, carbon black, and a curative system. This accelerator blend provides optimal tire wear and aging without significant loss in other properties like processing.

7. Rubber Composition for RFID Tag Coating in Tires with Insoluble Sulfur and Guanidine-Based Vulcanization Accelerator

BRIDGESTONE CORPORATION, 2024

RFID tag coating rubber composition for tires that balances communication performance, crack resistance, adhesion, and elastic modulus. The composition contains a rubber component, sulfur, silica, and a guanidine-based vulcanization accelerator. The sulfur is mainly insoluble and has a high content of 6.0 parts by mass per 100 parts rubber. The insoluble sulfur improves elastic modulus without blooming or tackiness issues. The guanidine accelerator prevents modulus loss and vulcanization decay.

US20240392153A1-patent-drawing

8. Compounds with Multiple Organic Thiosulfate Groups Based on 1,3,5-Triazinane Structure

Flexsys America L.P., 2024

Compounds with multiple organic thiosulfate groups for improving aging, adhesion, and vulcanization properties in rubber compositions. The compounds are represented by formula I: S,S′,S″-((1,3,5-triazinane-1,3,5-triyl)tris(R1-1,1-diyl)) tris(sulfurothioate), where R1 is a methyl, ethyl, or propyl group. These compounds can be made by reacting a haloalkylamine hydrohalide with a metal thiosulfate to form a Bunte salt, followed by deprotonation and reaction with an aldehyde. They can be used in vulcanizable elastomeric formulations at 0.1-5 parts per 100 parts elastomer to improve aging, adhesion, and

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9. Rubber Composition with EPDM for Non-Pneumatic Tire Spokes Incorporating Reinforcing Fillers and Curative System

BRIDESTONE AMERICAS TIRE OPERATIONS, LLC, 2023

Rubber composition for non-pneumatic tire spokes that provides ozone resistance and adhesion to cords without compromising fatigue and tear strength. The composition contains ethylene-propylene-diene terpolymer (EPDM) rubber along with a lower amount of another elastomer like natural rubber or polyisoprene. This balance improves ozone resistance while maintaining properties like adhesion and tear strength. The composition also includes reinforcing fillers like carbon black and silica for improved tear strength and degradation resistance. The curative system includes vulcanizing agents, accelerators, activators, inhibitors, and anti-scorching agents for curing the rubber.

US20230271450A1-patent-drawing

10. Elastomeric Compound Formulation with Specific Vulcanisation-Activating Fillers and Sequential Component Incorporation

PIRELLI TYRE S.p.A., 2023

Preparing elastomeric compounds for tyres with reduced zinc content, characterised by the incorporation of particular vulcanisation-activating fillers and by a precise sequence of adding some components of the compound. The preparation includes a number of components of the compound, a certain number of fatty acids, at least one product comprising zinc directly bound to a white filler, and at least one compatibilising agent (silane).

US11661498B2-patent-drawing

11. Triazinane Derivatives with Aminecarbotrithioate End-Groups for Dual Cross-Linking and Vulcanization Acceleration in Rubber Compounds

FLEXSYS AMERICA L.P., 2022

Triazinane derivatives with three aminecarbotrithioate end-groups that act as both cross-linking agents and vulcanization accelerators in rubber compounds. These triazinane compounds, like (1,3,5-triazinane-1,3,5-triyl)tris(propane-3,1-diyl) tris(dibenzylcarbamo(dithioperoxo)thioate), have dual effects during rubber vulcanization: they cross-link the rubber matrix by splitting their disulfide bonds, and they accelerate vulcanization by generating dithiocarbamate radicals. The compounds can be synthesized by reacting triazinane compounds with dithiocarbamate salts in water.

12. Silane Compound with Urea, Acid Amide, and Alkoxy Functional Groups for Rubber Crosslinking

Continental Reifen Deutschland GmbH, 2021

A silane compound for improving the durability of rubber compounds used in vehicle tires. The silane has a specific structure with functional groups that provide benefits when added to rubber mixtures. The silane has a urea group (-HNC(═O)NH-) for bonding to the rubber, an acid amide group (-HNC(═O) or -C(═O)NH-) for reacting with double bonds in the rubber, and alkoxy groups (-ORn, where R is an alkyl or aryl group) on the silicon atom for crosslinking during vulcanization. The silane improves tire durability by enhancing the rubber-silane bond strength, increasing rubber-silane crosslinking, and facilitating silane grafting onto the rubber.

13. Silane Compound with Reactive Functional Group and Hydrolyzable Group for Enhanced Polymer-Inorganic Material Interaction

ENEOS CORPORATION, 2021

A silane compound with high reactivity with organic polymers like rubber and high affinity with inorganic materials like silica or glass. The compound has a unique reactive functional group with low polarity and a hydrolyzable group. It improves dispersion and adhesion properties when mixed with low-polarity materials like rubber. The compound is useful as a silane coupling agent in rubber compositions and as an adhesion aid in adhesives and sealants. It can be synthesized by hydrosilylation of an alicyclic epoxy compound with trimethoxysilane or triethoxysilane in the presence of a hydrosilylation catalyst.

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14. Rubber Compound Utilizing Halogenated Graphite as Sole Vulcanization Activator

BRIDGESTONE CORPORATION, 2020

Rubber compound for making rubber products like tires without using zinc oxide as a vulcanization activator. The compound replaces zinc oxide with halogenated graphite. This allows reducing or eliminating zinc oxide for environmental benefits without compromising vulcanization and mechanical properties. The compound consists of a cross-linkable polymer base, reinforcing filler, sulfur, accelerants, and halogenated graphite as the sole vulcanization activator.

15. Rubber Composition with Enhanced Abrasion Resistance via Optimized Vulcanization Accelerator Distribution

SUMITOMO RUBBER INDUSTRIES, LTD., 2019

Rubber composition and tire with improved abrasion resistance by optimizing the distribution of vulcanization accelerators during compounding. The composition contains a sulfur atom-containing accelerator that disperses better in the rubber before adding fillers. This reduces adsorption of the accelerator onto fillers, allowing more uniform crosslinking during vulcanization. The dispersed accelerator is combined with a separate non-sulfur releasing accelerator. This prevents excessive crosslinking during kneading. The composition also contains zinc oxide as a catalyst carrier. The dispersed accelerators and filler-kneaded rubber are mixed with sulfur. This provides more uniform crosslink density and better abrasion resistance.

16. Rubber Composition Incorporating Vulcanization Aid with Specific Active Group Structure

SUMITOMO CHEMICAL COMPANY, LIMITED, 2019

Rubber composition with improved vulcanization rates for tire rubber, vibration dampers, belts, etc. The composition contains a vulcanization aid compound with a specific structure. The aid compound has an active group represented by formula (W) with a single bond connecting Z1 to another group. This group accelerates vulcanization of rubber components. The aid compound can have other substituents. The vulcanization aid improves cure rates when added to rubber compositions for products like tires.

US10287419B2-patent-drawing

17. Method for Producing Vulcanized Rubber Composition with Aminoguanidine-Enhanced Glass Transition Control

MITSUBISHI GAS CHEMICAL COMPANY, INC., 2018

A method for producing a vulcanized rubber composition with improved low temperature grip and reduced rolling resistance compared to conventional rubber compounds. The method involves adding a specific compound called aminoguanidine during the initial kneading step before vulcanization. The aminoguanidine compound helps control the rubber's glass transition temperature and loss tangent at 0°C and 60°C. This allows enhancing grip at low temps while reducing rolling resistance. The final vulcanized rubber composition contains the rubber, filler, coupling agent, aminoguanidine, sulfur, and vulcanization accelerator.

US20180355074A1-patent-drawing

18. Rubber Composition with Butyl Rubber, Liquid Polymer, Organic Peroxide, and Crosslinking Activator for Self-Sealing Tires

SUMITOMO RUBBER INDUSTRIES, LTD., 2018

Rubber composition for self-sealing tires with improved adhesion, sealing performance, fluidity, and processability. The composition contains a butyl rubber, liquid polymer, organic peroxide, and crosslinking activator. The liquid polymer has specific kinematic viscosities at 100°C and 40°C. The organic peroxide and crosslinking activator are in a specific range. This composition provides better properties like tensile elongation, adhesion, sealing, fluidity, and processability compared to similar compositions lacking these ingredients.

US20180201774A1-patent-drawing

19. Hydrocarbon Polymer Modifiers with Functional Groups for Anchoring to Fillers and Elastomers in Rubber Compounds

ExxonMobil Chemical Patents Inc., 2018

Using hydrocarbon polymer modifiers with functional groups to anchor them to fillers and/or elastomers in rubber compounds. This anchoring improves long term elastomeric performance, such as in tires. The modifiers are made by interpolymerizing hydrocarbon monomers like piperylenes, cyclic pentadienes, aromatics, limonenes, pinenes, and amylenes. Functional groups on the modifiers can be used to couple them to fillers like silica during rubber processing. This anchoring prevents migration of the modifiers to the surface over time and maintains compound properties. The functionalized modifiers can also be pre-reacted with crosslinking agents like organosilanes before adding them to the rubber mix.

US20180105631A1-patent-drawing

20. Rubber Composition with Glycerin Fatty Acid Ester, Silane Coupling Agent, and Activator for Enhanced Silica Dispersion

BRIDGESTONE CORPORATION, 2018

Rubber composition for tire with improved processability, low loss property, breaking resistance, and wear resistance. The composition contains a glycerin fatty acid ester, a silane coupling agent, and an activator added during kneading without the vulcanizing agent. This improves silica dispersion, reduces pre-vulcanization viscosity, and enhances low loss properties. The activator can be thioureas, ammonium thiocyanates, cysteines, thiadiazoles, zinc dialkyl dithiophosphates, or benzothiazoles. The fatty acid component of the ester is 10-90% of the total fatty acids.

US20180030215A1-patent-drawing

21. Polymer with Pendant Associative Groups Grafted onto Butadiene-Styrene Backbone

22. Rubber Composition with Thiazoline-Based Vulcanization System and Diene Elastomers

23. Functionalized Rubber with Terminators for Enhanced Filler Compatibility and Vulcanization

24. Rubber Composition with Thiadiazole-Based Vulcanization Accelerator and Diene Elastomers

25. Rubber Composition with Specific Additives for Pre-Cure Tread Retreading Method

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