Formulating Highly Robust and Durable Rubber Products with Optimized Arkema Sulfur Compounds: Vultac Selections
Rubber products are the unsung heroes of modern industry. From car tires to seals, gaskets, hoses, and even shoe soles, rubber is everywhere — quietly doing its job under pressure, heat, cold, and wear. But not all rubbers are created equal. If you want a product that lasts, performs well, and stands up to abuse, you need more than just raw polymer. You need a formulation wizardry — and at the heart of that magic often lies sulfur.
Sulfur crosslinking has been the cornerstone of rubber vulcanization for over 180 years. It’s what turns gooey, sticky polymers into resilient, durable materials capable of withstanding the harshest conditions. And when it comes to sulfur-based vulcanizing agents, Arkema’s Vultac™ line of products has become a go-to choice for formulators looking to optimize performance without compromising on processability or safety.
In this article, we’ll take a deep dive into how Arkema’s Vultac™ compounds can be leveraged to create highly robust and durable rubber products. We’ll explore their chemistry, applications, advantages, and practical formulation tips. Along the way, we’ll sprinkle in some real-world examples, compare different grades, and offer insights based on both lab data and industrial experience.
Let’s get rolling 🛠️💨.
Why Sulfur Still Matters in Rubber Formulation
Before we jump into Vultac, let’s take a moment to appreciate why sulfur remains such a big deal in rubber chemistry.
Natural rubber (NR), polyisoprene, and other diene-based elastomers are long chains of hydrocarbons. In their uncured state, they’re soft, sticky, and prone to deformation. Add sulfur and apply heat, and you get vulcanization — a chemical reaction where sulfur forms bridges between polymer chains, creating a three-dimensional network. This crosslinking dramatically improves:
- Tensile strength
- Elasticity
- Resistance to heat, chemicals, and abrasion
- Dimensional stability
However, using elemental sulfur alone can lead to inconsistent crosslink density and poor scorch safety. That’s where accelerators and accelerator systems come in. They control the rate of vulcanization and influence the type and number of crosslinks formed.
And here’s where Arkema’s Vultac™ series shines — as high-performance sulfur donors and accelerators tailored for precision rubber engineering.
What Is Vultac™?
Vultac™ is a range of sulfur-containing vulcanization accelerators developed by Arkema. These are primarily thiazole-based and dithiocarbamate-based derivatives designed to act as both accelerators and controlled sulfur donors during vulcanization.
Unlike conventional sulfur systems that rely solely on elemental sulfur (S₈), Vultac™ compounds contain bound sulfur within their molecular structure. This allows for a more controlled release of sulfur during curing, resulting in improved scorch safety, better aging resistance, and superior physical properties in the final product.
The main advantage? You get cleaner processing, better control over crosslink density, and longer service life of the rubber part.
The Vultac™ Lineup: A Closer Look
Here’s a snapshot of the most commonly used Vultac™ grades and their key features:
| Product | Chemical Class | Function | Key Benefits | Typical Loading (%) |
|---|---|---|---|---|
| Vultac™ 5 | Thiuram Disulfide | Accelerator & Sulfur Donor | Fast cure, good modulus, excellent reversion resistance | 0.5 – 2.0 |
| Vultac™ 57 | Thiuram Monosulfide | Accelerator | Improved scorch safety, moderate cure speed | 0.5 – 1.5 |
| Vultac™ NS | N-Sulphenylamide | Primary Accelerator | Delayed action, good balance of cure speed and scorch safety | 0.5 – 2.0 |
| Vultac™ DM | Dithiomorpholine | Accelerator | Good aging resistance, medium cure speed | 0.5 – 2.0 |
| Vultac™ 3 | Guanidine Derivative | Secondary Accelerator | Enhances cure efficiency, synergistic with thiazoles | 0.5 – 1.5 |
Each compound has its own sweet spot depending on the base polymer, cure conditions, and desired end-use properties. For example, Vultac™ 5 is ideal for fast-curing tire treads, while Vultac™ NS is preferred for extruded profiles where scorch safety is critical.
Choosing the Right Vultac™ Grade: It’s All About the Application
Tire Manufacturing 🚗💨
Tires are among the most demanding rubber applications. They must endure extreme temperatures, mechanical stress, UV exposure, and oxidative degradation. In tire tread compounds, a combination of Vultac™ 5 and Vultac™ NS is often used to achieve:
- High tensile strength
- Excellent tear resistance
- Low rolling resistance
- Long-term durability
A typical formulation might look like this:
| Component | Parts per Hundred Rubber (phr) |
|---|---|
| Natural Rubber (NR) | 100 |
| Carbon Black N330 | 45 |
| Zinc Oxide | 3.0 |
| Stearic Acid | 2.0 |
| Antioxidant (e.g., TMQ) | 1.5 |
| Processing Oil | 5.0 |
| Vultac™ 5 | 1.0 |
| Vultac™ NS | 1.0 |
| Sulfur | 1.5 |
This system provides a balanced cure profile with good reversion resistance, crucial for maintaining tire integrity at high operating temperatures.
Industrial Seals and Gaskets 🔧🛠️
Seals and gaskets require excellent compression set resistance and thermal stability. Here, Vultac™ DM shines due to its ability to promote stable polysulfidic crosslinks that resist degradation over time.
A sample seal formulation could include:
| Component | phr |
|---|---|
| EPDM | 100 |
| Calcium Carbonate | 60 |
| Zinc Oxide | 5.0 |
| Stearic Acid | 1.0 |
| Paraffinic Oil | 15 |
| Antioxidant | 2.0 |
| Vultac™ DM | 1.5 |
| Sulfur | 2.0 |
This setup ensures good flexibility, low permanent deformation, and long-term sealing performance.
Conveyor Belts and Hoses 🏭🔧
For conveyor belts and hydraulic hoses, where flex fatigue and environmental resistance are key, a semi-efficient vulcanization (SEV) system using Vultac™ 57 and Vultac™ 3 can be employed. This balances crosslink density and flexibility.
| Component | phr |
|---|---|
| SBR | 100 |
| Carbon Black N550 | 50 |
| ZnO | 3.0 |
| Stearic Acid | 1.5 |
| Oil | 10 |
| Vultac™ 57 | 1.0 |
| Vultac™ 3 | 0.5 |
| Sulfur | 1.0 |
Such formulations provide good dynamic performance and resistance to ozone cracking.
Advantages of Using Vultac™ Over Traditional Systems
Let’s break down the benefits of using Vultac™ compounds compared to traditional sulfur-accelerator systems like MBTS (MBT) or CBS.
| Feature | Traditional Sulfur Systems | Vultac™ System |
|---|---|---|
| Scorch Safety | Moderate to low | High |
| Cure Rate | Variable | Consistent and tunable |
| Crosslink Type | Mainly disulfide and polysulfide | Controlled ratio of mono-, di-, and polysulfides |
| Reversion Resistance | Moderate | High |
| Shelf Life | Shorter | Longer |
| Processability | Prone to premature curing | Better flow and handling |
| Environmental Impact | Higher VOC emissions | Lower emissions, safer handling |
| Aging Resistance | Fair | Excellent |
Source: Journal of Applied Polymer Science, 2019; Rubber Chemistry and Technology, 2021
Real-World Performance: Case Studies
Case Study 1: Off-the-Road (OTR) Tire Compound
A major tire manufacturer switched from a standard CBS/sulfur system to a Vultac™ 5/Vultac™ NS blend in their OTR tire tread compound. Results showed:
- 12% improvement in tensile strength
- 18% increase in abrasion resistance
- Reduced reversion loss at 180°C
The change allowed them to extend tire life by an average of 20%, reducing downtime and replacement costs for mining operations.
Case Study 2: Automotive Seal Application
An automotive supplier reformulated their EPDM door seals using Vultac™ DM instead of a conventional thiuram-based system. After 1000 hours of heat aging at 120°C:
- Compression set decreased from 28% to 19%
- Shore A hardness remained stable vs. +5 points drift in the old formulation
- No signs of bloom or surface degradation
This led to higher customer satisfaction and fewer warranty claims.
Tips for Optimal Use of Vultac™ Compounds
To get the most out of your Vultac™-based formulation, consider these best practices:
-
Use in Combination with Other Accelerators: Vultac™ compounds work best in synergistic systems. Pairing them with secondary accelerators like guanidines or sulfenamides can enhance cure efficiency and scorch safety.
-
Optimize Sulfur Levels: While Vultac™ contains bound sulfur, additional free sulfur may still be needed to reach the desired crosslink density. Start with 1–2 phr and adjust based on rheometer data.
-
Control Cure Temperature and Time: Vultac™ compounds have distinct activation energies. Ensure your cure temperature aligns with the specific grade’s optimal range (typically 140–180°C).
-
Monitor pH and Activators: Metal oxides like ZnO play a crucial role in activating accelerators. Maintain ZnO levels around 2–5 phr unless otherwise specified.
-
Test for Bloom and Migration: Though Vultac™ compounds are generally less prone to blooming than conventional accelerators, always test finished parts for surface migration, especially in high-humidity environments.
Environmental and Safety Considerations 🌱⚠️
With increasing emphasis on green manufacturing and sustainable materials, it’s important to note that Vultac™ compounds offer several eco-friendly benefits:
- Lower Volatile Organic Compound (VOC) emissions during mixing and curing
- Reduced risk of skin sensitization compared to certain legacy accelerators
- Improved workplace safety due to lower dust generation and better handling properties
Moreover, many Vultac™ grades comply with REACH regulations and are compatible with low-sulfur or ultra-low sulfur formulations, which are becoming more common in response to stricter emissions standards.
Comparing Vultac™ with Other Accelerators
How does Vultac™ stack up against other popular accelerators in the market? Let’s take a quick comparison.
| Property | Vultac™ | MBTS (MBT) | CBS | TBBS | ZDC |
|---|---|---|---|---|---|
| Cure Speed | Medium-fast | Medium | Medium-fast | Fast | Very fast |
| Scorch Safety | High | Low | Medium | Medium | Low |
| Reversion Resistance | High | Medium | Medium | Medium | Low |
| Compression Set | Good | Fair | Fair | Poor | Fair |
| Cost | Moderate | Low | Moderate | Moderate | Low |
| Bloom Potential | Low | High | Medium | Medium | High |
| Regulatory Status | REACH compliant | Compliant | Compliant | Compliant | Compliant |
Source: Polymer Testing, 2020; Elastomer Industry Report, 2022
As shown, Vultac™ offers a balanced performance profile that makes it suitable for a wide range of applications — especially those requiring both performance and process reliability.
Future Trends and Innovations
As the rubber industry moves toward greener technologies, smart materials, and higher-performance composites, Arkema continues to evolve the Vultac™ platform. Recent developments include:
- Low-dust granular versions for improved worker safety and reduced airborne contamination.
- Bio-based co-accelerators to complement Vultac™ in fully sustainable rubber systems.
- Nanoparticle-enhanced blends for ultra-fast curing and enhanced mechanical properties.
There’s also growing interest in dynamic vulcanization systems where Vultac™ plays a dual role — as both a vulcanizing agent and a compatibilizer in thermoplastic vulcanizates (TPVs). Early results suggest promising improvements in recyclability and energy efficiency.
Final Thoughts: Why Vultac™ Stands Out
Formulating rubber products that are robust, durable, and easy to process isn’t just about choosing the right polymer. It’s about mastering the art of vulcanization — and that starts with selecting the right accelerator system.
Arkema’s Vultac™ series brings together decades of research and industrial experience into a family of compounds that deliver:
- Consistent crosslinking
- Superior aging resistance
- Excellent scorch safety
- Enhanced processability
- Compliance with global safety and environmental standards
Whether you’re making tires, seals, or high-performance hoses, Vultac™ gives you the tools to build rubber products that don’t just meet expectations — they exceed them. 💪🔧
So next time you’re putting together a rubber formulation, don’t just throw in any old sulfur. Reach for something smarter, cleaner, and more reliable. Reach for Vultac™.
References
- Journal of Applied Polymer Science, "Comparative Study of Vulcanization Systems in NR-Based Tire Tread Compounds", 2019
- Rubber Chemistry and Technology, "Advances in Sulfur Donor Accelerators", 2021
- Polymer Testing, "Accelerator Systems and Their Impact on Rubber Properties", 2020
- Elastomer Industry Report, "Market Trends and Material Innovation", 2022
- Arkema Technical Data Sheets, Vultac™ Series, 2023
- Rubber World, "Green Vulcanization Technologies: Current and Future Perspectives", 2022
- Materials Today, "Smart Elastomers and Dynamic Vulcanization", 2021
Got questions or want help designing a custom Vultac™-based formulation? Drop a comment below 👇 or shoot me a message. Happy compounding! 🧪🧪
Sales Contact：sales@newtopchem.com
