Rubber Accelerator

What is accelerator

A rubber accelerator is a chemical additive used in the vulcanization (curing) process of rubber compounds to increase the rate of crosslinking between polymer chains, while simultaneously shortening the curing time and lowering the curing temperature required to achieve optimal physical properties.
Vulcanization, discovered by Charles Goodyear in 1839, is the process of converting raw, thermoplastic rubber into a durable, thermoset elastomer by forming sulfur bridges between polymer chains. Without accelerators, this reaction would be impractically slow — taking hours at high temperatures (above 160°C) and often resulting in uneven curing and poor mechanical performance. Accelerators act as catalysts or reaction intermediates that dramatically speed up the sulfur–rubber interaction, enabling complete vulcanization in minutes rather than hours.

Benefits of Accelerator

01/

Drastically Reduced Curing Time and Increased Throughput

The most immediate benefit of rubber accelerators is the dramatic acceleration of the vulcanization reaction. While unaccelerated sulfur vulcanization may require 4–6 hours at 140°C, the addition of a sulfenamide accelerator can reduce this to 2–5 minutes at the same temperature. This acceleration enables high-speed, continuous manufacturing processes such as injection molding, transfer molding, and extrusion, drastically increasing production throughput and reducing energy costs per unit. For manufacturers, this means shorter cycle times, higher output, and better utilization of expensive curing equipment..

02/

Lower Curing Temperatures — Energy Savings and Less Polymer Degradation

Accelerators allow vulcanization to proceed effectively at significantly lower temperatures than would otherwise be possible. Lower temperatures not only reduce energy consumption but also minimize the thermal degradation of heat-sensitive polymers (such as natural rubber and some synthetics) and prevent the breakdown of other compounding ingredients. This is particularly valuable for thick-section articles where uniform heat transfer is challenging — low-temperature curing with accelerators ensures more homogeneous crosslinking throughout the cross-section, avoiding undercured cores or overcured surfaces.

03/

Improved and More Consistent Physical Properties

Accelerators enable the formation of a more controlled and efficient crosslink network compared to unaccelerated sulfur systems. By directing the reaction toward monosulfidic and disulfidic crosslinks rather than long polysulfidic chains, accelerators produce vulcanizates with:
• Higher tensile strength and tear resistance
• Better abrasion resistance — critical for tires and conveyor belts
• Lower compression set — essential for seals and gaskets
• Improved dynamic properties — lower heat build-up and better fatigue resistance
Furthermore, the reproducibility of accelerator-based curing systems ensures batch-to-batch consistency, enabling manufacturers to meet tight quality specifications for automotive, aerospace, and medical applications.

04/

Greater Processing Safety and Scorch Resistance

Scorch — premature crosslinking during mixing, milling, or storage — is a major concern in rubber processing. Modern accelerators, especially sulfenamides, are designed with a built-in delay action: they remain dormant during mixing and early processing stages, only becoming fully active at vulcanization temperatures. This provides a wide safety margin for handling and shaping operations, allowing longer mold-filling times, better flow, and more complex part geometries. Once the compound enters the hot mold, however, the accelerator rapidly activates to produce a fast, complete cure — offering an excellent balance between processing safety and curing speed.

05/

Cost-Effectiveness — Lower Dosage, Higher Efficiency

Because accelerators are so potent, typical usage levels are only 0.5 to 2 parts per hundred rubber (phr) , representing a very small fraction of the overall compound cost. Yet, this small addition delivers huge benefits: it allows the sulfur level to be reduced (from 6–8 phr to 1–2 phr) while maintaining or even improving mechanical properties, reducing the risk of sulfur bloom, and improving aging resistance. The net result is lower raw material costs, higher product quality, and less waste — delivering a strong return on investment for compounders.

06/

Enables Advanced Formulations and Specialty Applications

Rubber accelerators unlock the potential for tailored curing systems that meet the demands of modern, high-value applications:
• Ultra-fast accelerators (e.g., ZBEC, TMTD) enable low-temperature curing for heat-sensitive latex products such as medical gloves, condoms, and balloons
• Nitrosamine-safe accelerators (e.g., ZBEC, TBBS) comply with stringent EU REACH regulations and FDA food-contact standards, making them essential for medical devices, infant products, and food-grade rubber goods
• Combinations of primary and secondary accelerators allow compounders to fine-tune the cure curve for optimal performance in tire treads (low rolling resistance, high wet grip), engine mounts (heat resistance, vibration damping), and seals (low compression set, chemical resistance)
Without the versatility of modern accelerators, many of today's high-performance rubber products — from fuel-efficient tires to biocompatible medical devices — simply would not exist. As sustainability and regulatory pressures continue to reshape the industry, the development of greener, safer, and more efficient accelerators remains at the forefront of rubber innovation, ensuring that manufacturers can meet both performance goals and environmental responsibilities.

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How is Accelerator Used in Industrial Processes?

Accelerators are widely used as vulcanizing agents in the rubber industry. It helps ensure excellent mechanical properties and performance of rubber compounds. It is also used as a metal chelating agent, an accelerator of the Doen-Rubber reaction and an industrial plasticizer. In addition to rubber, it is used in the production of adhesives, coatings and dyes. In addition to its use in industrial processes, it is also used in agriculture for soil disinfection and water treatment to remove pesticides and herbicides.

What is The Difference Between Accelerator And Catalyst?

An accelerator is a substance that increases the rate of a chemical reaction. It works by providing an alternate reaction pathway with a lower activation energy. Accelerators do not participate in the reaction themselves and are often used in polymerization reactions. A catalyst is a substance that increases the rate of a reaction by lowering the activation energy without being consumed in the reaction. Catalysts do not affect the position of the equilibrium nor do they affect the thermodynamics of the reaction. Catalysts are often used in industrial chemical processes to increase the rate of the reaction or reduce the amount of energy required. The main difference between these two is that an accelerator is involved in the reaction whereas a catalyst is not.

What Are The Properties of Accelerator ?

Accelerators can include physical, chemical, and toxicological properties that may be affected by their molecular structure, reactivity, and intended application. These properties can be evaluated and monitored using a variety of analytical techniques such as spectroscopy, chromatography, and toxicity testing methods, among others. It is important to handle and dispose of such compounds with care.

Is Accelerator Compatible With Other Rubber Accelerators And Activators?

The compatibility of accelerators with other rubber chemicals and additives depends on their chemical structures, molecular weights, and functionalities. Some accelerators may be compatible and mutually reinforcing with each other, while others may be incompatible or even react with each other, leading to adverse effects on the rubber vulcanization and properties. It is essential to carefully select and balance the types and amounts of rubber chemicals to achieve desired vulcanization and performance characteristics.

Application of Accelerator

Tire manufacturing
Accelerator is widely used in the production of tires. It is used to improve the processing properties of rubber, such as its vulcanization rate, and to enhance the mechanical properties of the tire, such as its durability, toughness, and resistance to wear.

Industrial rubber products
Accelerator is also used in the production of other rubber products such as belts, hoses, seals, gaskets, and other types of industrial rubber. It helps to improve the properties of the rubber, making it more durable, resistant to wear, and able to withstand extreme temperatures.

Adhesives
Accelerators are also used in the production of adhesives. It acts as a cross-linking agent, helping to improve the bonding properties and durability of the final product.

Wire and cable insulation
Accelerator is used in the production of wire and cable insulation. It helps improve the properties of the insulation by making it more resistant to heat and aging, and enhancing its mechanical properties.

Footwear
Accelerators are used in the production of various types of footwear such as sneakers, boots and sandals. It helps improve the mechanical properties of rubber, making it more durable, wear-resistant and able to withstand the harsh conditions of daily use.

How Can The Effectiveness of Accelerator Be Maximized In Rubber Products?

Selection of the right accelerator

The selection of the right accelerator with the appropriate properties is important to maximize its effectiveness. Different types of accelerators are available in the market, and each has a set of unique properties that make it better suited for certain applications.

Proper dosage

The right amount of accelerator should be used to balance the properties of the rubber product. Overdosing or underdosing can lead to issues with the product's quality or performance.

Proper mixing

Proper mixing is critical to ensure the accelerator is evenly dispersed throughout the rubber. Uneven dispersion can lead to inconsistent product performance.

Adequate curing time and temperature

The curing time and temperature can significantly affect the effectiveness of the accelerator. Proper curing conditions should be maintained to ensure complete curing, avoiding any detrimental effects on the product's properties.

Optimization of other formulation components

Other formulation components, such as the type and amount of cross-linkers or fillers, can affect the effectiveness of the accelerator. The optimal combination of these components should be determined to achieve the desired properties of the rubber product.

Is Accelerator Used in Food or Pharmaceutical Industries?

Accelerators are used in both food and pharmaceutical industries. In the food industry, they are used as additives to hasten the process of fermentation, ripening, and other chemical reactions. In the pharmaceutical industry, they are used to speed up the manufacturing processes of medicines like vaccines and antibiotics. Some accelerators are also used in diagnostic testing and medical research.

What Are The Safety Precautions To Take While Handling Accelerator ?

Wear appropriate personal protective equipment (PPE) such as gloves, goggles, and lab coats. Work in a well-ventilated area to minimize exposure to fumes and vapors. Use this substance only in designated areas or equipment. Do not eat, drink, or smoke while working with chemicals. Follow the storage and handling instructions provided on the product label or Material Safety Data Sheet. Use caution when opening containers to avoid spillage of substance. In case of contact with skin or eyes, wash affected area immediately with plenty of water and seek medical advice. Clearly label all containers with the chemical name, hazard and date of last inspection.

What Are The Physical And Chemical Properties of Accelerator?

Physical properties
Accelerators can be solids, liquids, or gases depending on their chemical nature and intended application. Accelerators can be colorless or have a distinct color, depending on the chemical nature and additives. The density of accelerators typically ranges from 0.8 g/cm^3 to 3 g/cm^3. Accelerators can be soluble or insoluble in water, depending on the chemical nature and intended application. The melting and boiling points of accelerators vary widely depending on their chemical nature.

Chemical properties
Accelerators are typically reactive to certain chemicals, particularly those involved in chemical reactions. Accelerators can be stable or unstable depending on their chemical nature. The pH of accelerators can vary depending on the chemical nature and intended application. Accelerators can be flammable or non-flammable depending on their chemical nature. Accelerators can be toxic or non-toxic depending on their chemical nature and concentration.

What is the composition of accelerator ?

The core composition is based on amines + carbon disulfide + (optionally) zinc/metal oxides for ultra-accelerators, or benzothiazole + amine derivatives for sulfenamides. The active chemical structure determines the reaction mechanism, while the added fillers affect physical handling characteristics. If you have a specific grade in mind, we can provide its exact compositional breakdown and SDS.

What is The Recommended Storage Condition For Accelerator?

It should be stored at room temperature and avoid high or low temperatures or even freezing. Keep out of direct sunlight and store in a cool, dry place. It should be kept as dry as possible to prevent moisture absorption and dampness. Should be stored in sealed containers or packages to avoid the effects of oxygen, moisture and other contaminants. Accelerators should be stored separately to avoid contact with other chemicals. Severe vibration and mechanical vibration should be avoided to reduce the decomposition of the accelerator.

How To Improve The Stability of Accelerator

Choose high-quality accelerator raw materials, such as chemicals with high purity and good stability. Strengthen production and quality control, strictly control the production process, and ensure that parameters such as temperature, pressure, and reaction time during the accelerator production process are reasonably and stably controlled. According to the needs of different application fields, combined with the product characteristics and physical and chemical environments of different application fields, optimize the accelerator formula. By coating the accelerator, its service life can be extended and its stability can be maintained. Pay attention to storage conditions, such as avoiding light, moisture, and high temperatures. At the same time, choosing appropriate packaging materials can effectively avoid the contamination and volatilization of accelerators. Adding a certain amount of antioxidants to the accelerator can improve the stability of the accelerator and extend its service life.

How Do Accelerators Improve Accelerated Reactions?

Lowering the Activation Energy of Crosslinking

Accelerators reduce the thermal energy barrier required for sulfur to react with rubber chains. This means vulcanization can proceed at lower temperatures or in shorter time at the same temperature compared to unaccelerated sulfur systems, making the reaction kinetically faster.

Generating More Reactive Intermediate Complexes

Accelerators (especially sulfenamides and thiurams) react with sulfur, zinc oxide, and stearic acid to form highly reactive zinc‑accelerator‑sulfur complexes. These intermediates are much more electrophilic than elemental sulfur alone, enabling rapid attack on the allylic hydrogen atoms of the rubber backbone and drastically speeding up crosslink formation.

Shifting the Reaction Pathway to a More Efficient Route

Without an accelerator, sulfur vulcanization follows a slow, inefficient free‑radical pathway that produces long, unstable polysulfidic crosslinks. Accelerators redirect the reaction through a concerted ionic or polar mechanism, which not only accelerates the overall rate but also ensures more uniform crosslink distribution—achieving optimum cure in minutes instead of hours.

Enabling Synergistic Activation with Secondary Accelerators

When used in combination (e.g., a primary sulfenamide plus a secondary thiuram or dithiocarbamate), accelerators create a synergistic effect that further boosts the cure rate. The secondary accelerator rapidly activates at vulcanization temperature, while the primary provides scorch safety during processing. This dual system accelerates the reaction more effectively than either component alone, giving compounders the ability to fine‑tune cure speed for high‑output manufacturing.

FAQ

Q: What is an accelerator?

A: An accelerator is a chemical substance used to speed up certain chemical reactions. They are widely used in the manufacture of various products such as plastics, rubber, paints, glues, cosmetics, etc.

Q: What types of accelerators are there?

A: There are many types of accelerators, which can be divided into many types according to different chemical reactions and application fields, such as oxidants, reducing agents, acid catalysts, alkali catalysts, metal catalysts, etc.

Q: What is the function of accelerator?

A: The role of accelerators is to speed up chemical reactions and increase their efficiency. Promoters can also change reaction selectivity and product structure.

Q: How do I choose the right accelerator for my rubber compound?

A: Selecting the right accelerator depends on your rubber type (NR, SBR, NBR, EPDM, etc.), curing temperature, processing safety requirements, and final product properties. Accelerators are generally classified by cure speed and scorch safety

• Sulfenamides (CBS, TBBS, DCBS) – offer the best processing safety (delayed action) and are the most commonly chosen primary accelerators for general-purpose elastomers
• Thiazoles (MBT, MBTS) – provide intermediate scorch safety and moderate cure speed
• Thiurams (TMTD, TMTM) – ultra-fast accelerators, often used as secondary accelerators
• Dithiocarbamates (ZDBC, ZDEC, ZBEC) – very fast, low-temperature curing; ZBEC offers the best scorch resistance among dithiocarbamates
In practice, a single accelerator rarely achieves optimal results
. We can recommend a primary/secondary accelerator system tailored to your specific formulation and processing conditions.

Q: What is scorch (premature vulcanization) and how can I prevent it?

A: Scorch is the premature crosslinking of rubber during mixing or processing, before the compound reaches the mold. It leads to poor flow, surface defects, and scrapped material.
To prevent scorch:
• Choose an accelerator with adequate scorch safety for your processing window – sulfenamides offer the best delay action
• Keep processing temperatures below the accelerator's activation threshold
• Ensure proper dispersion of all compounding ingredients
• Consider using a retarder (e.g., PVI) to extend scorch time for complex or high-temperature operations
If scorch occurs, reduce the accelerator dosage, switch to a slower accelerator, or lower your processing temperature

Q: What is "blooming" on the rubber surface, and how can I prevent it?

A: Bloom appears as a white, powdery, or oily substance on the surface of vulcanized rubber parts. It occurs when an ingredient (accelerator, sulfur, or other additives) exceeds its solubility limit in the rubber matrix and migrates to the surface.
To prevent blooming:
• Keep accelerator and sulfur dosages within their solubility limits for your rubber type
• Ensure uniform dispersion during mixing
• Avoid over-curing, which can force additives out of the matrix
• For ultra-fast accelerators like thiurams and dithiocarbamates, use them sparingly or in combination with slower accelerators
Bloom is not always harmful – in some cases it can provide surface protection – but for aesthetic or adhesion-critical applications, it should be avoided.

Q: How to choose the appropriate accelerator?

A: Selecting a suitable accelerator requires consideration of multiple factors, such as required modification effect, processing conditions, cost, etc. At the same time, it is also necessary to consider whether the accelerator is compatible with other materials and whether it is stable.

Q: How to store accelerator?

A: The accelerator should be stored in a dry, cool, and ventilated place to avoid contact with air, moisture, sunlight, etc. At the same time, safety operating procedures should be followed and avoid storage near fire and heat sources.

Q: Can accelerators increase the purity of reaction products?

A: The role of accelerators in reactions is mainly to increase reaction rate and efficiency, but some accelerators can also be used to adjust the chemical configuration and product selectivity of reaction products, thereby improving the purity of reaction products.

Q: What is the difference between accelerator and catalyst?

A: Both accelerators and catalysts are used to increase the rate and efficiency of chemical reactions, but catalysts react with the substrate but do not participate in the reaction themselves, while accelerators participate in the reaction and play a role in the reaction process.

Q: Why is it necessary to use accelerators?

A: The use of accelerators can significantly increase reaction rate and efficiency, reduce reaction activation energy, speed up the reaction process, increase yield and purity, and save production costs.

Q: What is the difference between accelerator and catalyst?

A: Promoters and catalysts are similar but not identical concepts. Accelerator is a broad concept, including all substances that can promote chemical reactions, promote material changes and transformations; catalysts are one of them, specifically referring to those substances that can reduce the reaction activation energy, increase the reaction rate, and do not participate in the reaction itself.

Q: Will the use of accelerator affect the quality of the product?

A: The use of accelerators may have a significant impact on product quality. However, this effect depends on the type of accelerator used, its dosage and the specific application scenario. Correct use of accelerators and reasonable control of their usage can produce better results and enhance product quality.

Q: What are the applications of accelerators in production and research reactions?

A: In production, accelerators are widely used in reaction processes in chemical, biological, pharmaceutical, food and other industries to promote reaction speed, reduce energy consumption, improve yield and selectivity, etc. In research, accelerators can help researchers delve deeper into reaction mechanisms and analyze intermolecular interactions.

Q: What are the applications of accelerators in chemical reactions?

A: Accelerators are used in a wide range of applications, including chemical industry, bioengineering, pharmaceutical manufacturing, etc. They can help chemical reactions proceed faster, increasing product yield and purity.

Q: When is it necessary to use accelerators?

A: Enhance material properties: Adding accelerators will improve the strength, hardness, toughness and other properties of the material. Increase adhesion: In the production of adhesives or coatings, adding accelerators can speed up curing or increase adhesion.

Q: What are the ways to use accelerators?

A: The accelerator can be added to the reaction system by adding raw materials, dissolving, precipitating, etc., or it can be directly added to the reactants during the reaction process for promotion. Pay attention to operational safety and dosage control.

Q: Can I get a free sample before placing a bulk order?

A: Yes, we provide free samples for most of our rubber accelerator products. Samples are available for lab testing, formulation evaluation, and cure curve analysis. While the samples are free of charge, the shipping cost is typically borne by the buyer

Q: What is your minimum order quantity (MOQ) and delivery lead time?

A: Our MOQ varies by product and grade:
• Standard accelerators (CBS, TBBS, MBT, MBTS): typical MOQ of 500 kg – 1 ton
• Specialty or ultra-fast accelerators (ZBEC, ZDBC, TMTD): we can accommodate trial quantities starting from 25 kg
• For some products, we accept sample quantities as low as 1 kg with sample charges applied
Delivery lead time: Typically 7–15 working days after order confirmation, depending on the product and quantity
. For large-volume contracts (above 30 tons), lead time may be extended and is subject to negotiation.
We accept T/T (30% deposit, 70% before shipment) and L/C as standard payment terms.

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