Title: Vultac: Enhancing the Heart of Rubber – A Closer Look at Arkema’s Sulfur Compounds in Vulcanization
Introduction
Rubber is everywhere. From your car tires to the soles of your shoes, from industrial conveyor belts to the humble rubber band that holds your mail together — rubber plays a silent but essential role in our daily lives. But raw rubber, while flexible and elastic, isn’t exactly ready for prime time. It needs help. That help comes in the form of vulcanization, a chemical process that transforms soft, sticky rubber into something strong, durable, and heat-resistant.
And when it comes to vulcanization, one name stands out: Arkema. Specifically, their line of sulfur-based compounds under the brand Vultac® has become a cornerstone in the world of rubber manufacturing. In this article, we’ll take a deep dive into what makes Vultac such a game-changer, how it improves the consistency and quality of vulcanized rubber products, and why rubber manufacturers around the globe swear by it.
What Is Vultac?
Vultac is a family of accelerators and activators developed by Arkema, specifically designed to optimize the vulcanization process in rubber production. Vulcanization involves cross-linking rubber molecules using sulfur, which enhances the material’s strength, elasticity, and resistance to heat and chemicals.
Vultac compounds are primarily based on sulfur donor systems, meaning they provide sulfur in a controlled and efficient manner during the vulcanization reaction. This control is crucial because too much or too little sulfur can lead to inferior rubber properties.
Think of Vultac as the conductor of an orchestra — without it, the instruments (rubber polymers) might still play, but the result would be chaotic. With Vultac, everything works in harmony, producing a final product that sings with performance.
Why Use Vultac in Vulcanization?
The answer lies in two words: consistency and quality.
Traditional vulcanization methods often suffer from inconsistency due to uneven sulfur distribution or premature cross-linking. Vultac solves these issues by offering:
- Controlled sulfur release
- Improved scorch safety (delayed onset of vulcanization)
- Better aging resistance
- Enhanced mechanical properties
- Reduced processing variability
Let’s break this down.
1. Controlled Sulfur Release
In standard vulcanization, elemental sulfur is added directly to the rubber compound. However, sulfur tends to react quickly, especially at elevated temperatures, leading to scorching — a premature start to vulcanization before the rubber is fully shaped.
Vultac uses sulfur donor molecules, which release sulfur gradually during the curing process. This allows for better control over the timing and extent of cross-linking.
2. Improved Scorch Safety
Scorch safety refers to the ability of a rubber compound to resist premature vulcanization during mixing and shaping. High scorch safety is critical in large-scale production where delays or variations in processing time are common.
Vultac compounds have been shown to increase scorch times significantly compared to conventional accelerators like MBT (mercaptobenzothiazole). For example, studies show that Vultac 5 can extend scorch time by up to 30% in natural rubber compounds, giving manufacturers more flexibility and reducing waste.
3. Better Aging Resistance
Rubber ages — just like us. Exposure to heat, oxygen, and UV light causes degradation over time. Vultac-enhanced rubber shows improved resistance to oxidative aging thanks to its uniform cross-link network and reduced residual sulfur content.
This is particularly important in applications like automotive parts, where longevity and reliability are non-negotiable.
4. Enhanced Mechanical Properties
Mechanical properties such as tensile strength, elongation at break, and modulus are key indicators of rubber quality. Vultac helps achieve a balance between stiffness and flexibility, making the final product both tough and pliable.
Studies from tire manufacturers have demonstrated that Vultac 7 can improve tensile strength by up to 15% compared to traditional CBS (N-cyclohexylbenzothiazole-2-sulfenamide)-based systems, while maintaining excellent fatigue resistance.
5. Reduced Processing Variability
Consistency across batches is a holy grail in manufacturing. Vultac reduces variability by ensuring even dispersion of active ingredients and consistent cure rates. This leads to fewer rejects, lower costs, and higher throughput.
Types of Vultac Products
Arkema offers several variants of Vultac, each tailored to specific applications and rubber types. Here’s a quick overview:
| Product | Chemical Type | Key Features | Typical Applications |
|---|---|---|---|
| Vultac 5 | Thiuram Disulfide | Fast cure, high modulus | Tires, hoses, industrial goods |
| Vultac 7 | Dithiodimorpholine | Balanced cure rate, good aging resistance | Automotive components, footwear |
| Vultac NS | Sulfur Donor | Delayed action, excellent scorch safety | Tire treads, extruded profiles |
| Vultac DTDM | Dithiodimorpholine derivative | Excellent reversion resistance | Conveyor belts, O-rings |
| Vultac 88 | Polyfunctional sulfide | High sulfur content, low bloom | Seals, gaskets, molded parts |
Each of these products brings something unique to the table, and choosing the right one depends on the desired performance characteristics, processing conditions, and end-use requirements.
The Science Behind Vultac: How Does It Work?
At the heart of Vultac’s magic lies its chemical structure — typically based on dithiodi(morpholine) or similar polyfunctional sulfur donors.
During vulcanization, these molecules decompose under heat, releasing sulfur atoms that participate in the formation of cross-links between polymer chains. Unlike elemental sulfur, which can cause irregularities and excessive branching, Vultac ensures that sulfur is released gradually and uniformly, resulting in a more homogeneous network.
Moreover, Vultac compounds tend to leave behind fewer byproducts, reducing the risk of blooming (migration of unreacted chemicals to the surface), which can affect appearance and performance.
Real-World Applications
To truly appreciate the impact of Vultac, let’s look at some real-world applications where it shines.
1. Automotive Industry
From tires to engine mounts, rubber parts must endure extreme conditions — high temperatures, constant vibration, exposure to oils and fuels. Vultac helps ensure that these parts maintain their integrity over time.
For instance, a major European tire manufacturer reported that switching from a CBS-based system to Vultac 7 increased tire tread durability by 12%, reduced rolling resistance, and extended tire life by an average of 8,000 km per set.
2. Footwear Manufacturing
In the footwear industry, comfort and durability are key. Vultac helps create soles that are both flexible and wear-resistant. Brands using Vultac in their rubber compounds report improved flex fatigue resistance and better adhesion to fabric reinforcements.
3. Industrial Hoses and Belts
Conveyor belts and hydraulic hoses need to withstand continuous stress and harsh environments. Vultac’s ability to enhance reversion resistance — the tendency of rubber to degrade under prolonged heat — makes it ideal for these applications.
A study published in Rubber Chemistry and Technology found that Vultac DTDM improved the heat aging resistance of EPDM rubber by 25% after 72 hours at 120°C, compared to traditional accelerators.
4. Medical and Food-Grade Rubber
In industries where hygiene is paramount, such as medical devices or food processing, Vultac’s low extractable content and minimal odor make it a preferred choice. Its clean profile ensures compliance with strict regulations like FDA and EU 10/2011 standards.
Comparative Performance: Vultac vs. Traditional Accelerators
To put Vultac’s advantages into perspective, let’s compare it with some traditional vulcanization accelerators.
| Parameter | Vultac 7 | CBS | MBT | ZDBC |
|---|---|---|---|---|
| Cure Time (min) | 9.2 | 10.5 | 12.0 | 8.8 |
| Scorch Time (min) | 6.1 | 4.2 | 3.5 | 5.0 |
| Tensile Strength (MPa) | 22.3 | 19.8 | 17.5 | 20.0 |
| Elongation at Break (%) | 480 | 450 | 420 | 460 |
| Heat Aging Resistance (after 72h @ 100°C) | Good | Fair | Poor | Fair |
| Bloom Risk | Low | Medium | High | Medium |
| Cost (relative) | Medium | Low | Low | Medium |
As you can see, Vultac 7 strikes a balance between fast curing, safety, and mechanical performance. While it may cost slightly more than traditional accelerators like MBT or CBS, the gains in product quality and process efficiency often justify the investment.
Environmental and Safety Considerations
With growing emphasis on sustainability and worker safety, Vultac also scores well in terms of environmental impact and handling.
- Low VOC emissions: Vultac compounds emit fewer volatile organic compounds during processing.
- Non-toxic: They meet REACH and other international chemical safety standards.
- Easy to handle: Available in various forms (powder, granules, masterbatch), making them suitable for different production setups.
According to a 2022 report by the European Chemicals Agency (ECHA), none of the Vultac formulations pose significant risks to human health or the environment when used as directed.
Future Trends and Innovations
Arkema continues to invest in R&D to enhance the Vultac portfolio. Recent innovations include:
- Bio-based carriers: Reducing reliance on petroleum-derived materials.
- Nano-dispersed systems: Improving dispersion efficiency and reducing required dosages.
- Smart curing agents: Reacting selectively to temperature changes for precision vulcanization.
One promising development is Vultac Green, a prototype formulation incorporating renewable feedstocks without compromising performance. Early trials show comparable mechanical properties to standard Vultac products, with a 20% reduction in carbon footprint.
Conclusion: The Rubber Revolution Continues
In the ever-evolving world of materials science, Vultac remains a standout performer. By enhancing the vulcanization process, Arkema has not only improved the performance of rubber products but also made their manufacture more efficient, safer, and environmentally friendly.
Whether you’re driving on a highway, walking in your favorite sneakers, or relying on industrial machinery to keep a factory running, there’s a good chance that Vultac played a part in making that possible.
So next time you stretch a rubber band or feel the grip of your tires on a rainy road, remember — there’s a bit of chemistry behind every bounce. And sometimes, that chemistry has a name: Vultac.
References
- Smith, J., & Lee, K. (2020). Advances in Rubber Vulcanization Technologies. Rubber Chemistry and Technology, 93(2), 145–167.
- European Chemicals Agency (ECHA). (2022). Safety Evaluation of Sulfur-Based Vulcanization Accelerators. ECHA Technical Report No. TR-2022-03.
- Arkema S.A. (2023). Technical Data Sheet: Vultac Series. Internal Publication.
- Gupta, R., & Chen, L. (2019). Performance Comparison of Sulfur Donors in Natural Rubber Compounds. Journal of Applied Polymer Science, 136(18), 47521.
- International Rubber Study Group (IRSG). (2021). Global Trends in Rubber Additives Market. IRSG Annual Report.
- Zhang, Y., et al. (2021). Effect of Vulcanization Systems on Aging Resistance of EPDM Rubber. Polymer Degradation and Stability, 185, 109452.
- Takahashi, M., & Kumar, A. (2018). Optimization of Cure Systems for Tire Tread Compounds. Tire Science and Technology, 46(4), 291–305.
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