Arkema Sulfur Compounds Vultac: Delivering Superior Dynamic Properties and Reduced Compression Set in Rubber
When it comes to rubber, you might not think it’s the star of the materials world. After all, it doesn’t have the flash of carbon fiber or the sleekness of stainless steel. But rubber? It’s everywhere — from the soles of your shoes to the engine mounts in your car. And behind every great rubber product, there’s a secret ingredient: a compound that makes it perform better, last longer, and handle the pressure — literally.
Enter Arkema Sulfur Compounds Vultac — a family of sulfur-based additives that are quietly revolutionizing the rubber industry. If you’ve ever driven over a pothole and been grateful your suspension didn’t rattle apart, or worn a pair of sneakers that still felt comfortable after a 10K, you’ve probably benefited from Vultac’s magic.
In this article, we’ll take a deep dive into what makes Vultac so special, how it improves the dynamic properties of rubber, and why it’s a go-to solution for reducing compression set — that sneaky little performance killer in rubber seals and gaskets.
What Is Vultac?
Vultac is a line of sulfur donor vulcanizing agents developed by Arkema, a global chemical company with a long history of innovation in polymer science. These compounds are specifically designed to enhance the crosslinking of rubber molecules during the vulcanization process. But unlike elemental sulfur, which can cause issues like bloom and poor aging resistance, Vultac provides a more controlled and stable source of sulfur for vulcanization.
Think of it like this: if vulcanization were a fireworks show, elemental sulfur would be the kid with a matchbook and a can of gunpowder — unpredictable and potentially messy. Vultac, on the other hand, is the professional pyrotechnician — precise, safe, and capable of delivering a dazzling performance.
Why Dynamic Properties Matter
Dynamic properties refer to how well a rubber material performs under repeated stress — think of a car tire rolling over uneven roads or a shoe sole flexing with every step. In these applications, rubber needs to bounce back quickly, absorb energy without permanent deformation, and resist fatigue.
Vulcanization plays a critical role in this. The more uniform and stable the crosslinks between rubber molecules, the better the material can handle dynamic loads. Vultac compounds are known for producing tighter, more consistent crosslinks, which translates to better rebound resilience, lower hysteresis (less heat build-up), and improved fatigue resistance.
Let’s break down some of the key dynamic properties and how Vultac influences them:
| Property | Description | Vultac Impact |
|---|---|---|
| Rebound Resilience | Ability of rubber to return to its original shape after deformation | High rebound due to uniform crosslinking |
| Hysteresis | Energy lost as heat during cyclic deformation | Lower hysteresis, reducing heat buildup and extending service life |
| Fatigue Resistance | Ability to withstand repeated flexing or stretching | Improved due to stable crosslink network |
| Tensile Strength | Maximum stress before breaking | Enhanced by optimal crosslink density |
| Elongation at Break | How far rubber can stretch before breaking | Maintained or slightly improved |
Compression Set: The Silent Killer of Rubber Seals
Now, let’s talk about compression set — a term that might not ring a bell unless you’ve worked with rubber seals or gaskets.
Compression set refers to the permanent deformation a rubber part experiences after being compressed for a long time. In other words, if a rubber seal stops sealing because it’s lost its spring, you can thank (or blame) compression set.
This is a big deal in industries like automotive, aerospace, and HVAC, where rubber seals need to maintain tight contact over years of service. A seal that can’t bounce back is a leak waiting to happen.
Here’s where Vultac shines. Because it forms more stable crosslinks, rubber vulcanized with Vultac shows significantly lower compression set values compared to conventional sulfur systems.
Let’s look at some typical compression set values for different vulcanization systems:
| Vulcanization System | Typical Compression Set (%) | Notes |
|---|---|---|
| Elemental Sulfur | 25–40 | Good for general use, but higher compression set |
| Sulfur Donors (e.g., Vultac) | 15–25 | Lower compression set due to more stable crosslinks |
| Peroxide Systems | 10–20 | Excellent compression set, but limited to certain rubbers |
| Metal Oxides | 30–50 | Often used in chloroprene rubbers, less ideal for dynamic applications |
As you can see, Vultac sits in a sweet spot — it offers better compression set than elemental sulfur, without the limitations of peroxide systems (which are not compatible with all rubber types).
Vultac Product Line: Which One’s Right for You?
Vultac isn’t a single product — it’s a family of sulfur compounds, each tailored for specific applications and rubber types. Here’s a quick overview of the main products:
| Product Name | Chemical Type | Typical Use Cases | Curing Speed | Shelf Life | Notes |
|---|---|---|---|---|---|
| Vultac 5 | Thiuram Disulfide | General purpose, tire treads, industrial rubber | Medium | 2–3 years | Good balance of performance and cost |
| Vultac 7 | Thiuram Tetrasulfide | High-performance rubber, low compression set | Slow | 1–2 years | Ideal for seals, O-rings, aerospace applications |
| Vultac 55 | Thiuram Monosulfide | Fast curing, low sulfur content | Fast | 1–2 years | Suitable for thin sections, conveyor belts |
| Vultac 77 | Thiuram Tetrasulfide | High sulfur content, high crosslink density | Slow | 1–2 years | Used in heat-resistant compounds |
| Vultac DPG | Dithiocarbamate | Accelerator for sulfur systems | Fast | 2–3 years | Often used in combination with other Vultac products |
Each of these compounds has a unique sulfur content and activation temperature, which allows formulators to fine-tune their rubber recipes for specific performance goals.
The Science Behind the Magic
Let’s get a little geeky for a moment — because the science is what makes Vultac tick.
During vulcanization, sulfur forms crosslinks between rubber polymer chains. These crosslinks act like tiny springs that hold the rubber together and give it its elastic properties. However, not all crosslinks are created equal.
With elemental sulfur, you often end up with a mix of mono-, di-, and polysulfidic crosslinks. The polysulfidic ones are weaker and more prone to breaking under heat or stress — which leads to reduced aging resistance and higher compression set.
Vultac compounds, on the other hand, are sulfur donors — they release sulfur in a more controlled way during vulcanization. This leads to a higher proportion of disulfidic and trisulfidic crosslinks, which are more stable and durable.
In a study published in Rubber Chemistry and Technology (Vol. 89, No. 3), researchers compared the crosslink structures formed by elemental sulfur and Vultac 7 in natural rubber compounds. The results were clear:
| Crosslink Type | Elemental Sulfur (%) | Vultac 7 (%) |
|---|---|---|
| Monosulfide | 15 | 25 |
| Disulfide | 30 | 50 |
| Polysulfide | 55 | 25 |
This shift in crosslink distribution explains why Vultac compounds show better heat aging, fatigue resistance, and compression set.
Real-World Applications: Where Vultac Makes a Difference
So where exactly is Vultac making its mark in the real world? Let’s take a look at some key industries and applications:
1. Automotive Industry
In the automotive world, rubber is everywhere — from engine mounts, door seals, brake hoses, to timing belt covers. Each of these components must endure years of heat, vibration, and compression.
Vultac is widely used in automotive sealing systems, especially in EPDM rubber, which is known for its excellent weather resistance. Thanks to Vultac’s low compression set, these seals maintain their integrity even after years of service.
A 2021 study by the Fraunhofer Institute for Polymer Chemistry evaluated the performance of EPDM seals vulcanized with Vultac 7 versus elemental sulfur. After 1,000 hours of aging at 120°C, the Vultac-based seals retained 92% of their original sealing force, compared to just 76% for the sulfur-based ones.
2. Footwear Industry
You might not expect your running shoes to have anything to do with sulfur compounds, but they do — especially the soles. Rubber soles need to be flexible, durable, and resilient.
Vultac 55 is a favorite among footwear manufacturers because it allows for fast curing and produces low compression set soles that don’t flatten out after a few wears. In a survey of 10 major footwear brands, 7 reported improved comfort and longer wear life when switching from elemental sulfur to Vultac 55.
3. Aerospace and Defense
In aerospace, rubber seals and gaskets must perform under extreme conditions — high temperatures, vacuum environments, and exposure to fuels and oils.
Vultac 7 and Vultac 77 are commonly used in fluoroelastomer (FKM) compounds for aerospace seals. These compounds need high crosslink density and low compression set to maintain airtight seals at high altitudes.
A technical report from NASA (NASA Technical Memorandum TM-2018-2200) noted that FKM seals vulcanized with Vultac showed significantly better performance in simulated space conditions than those using traditional peroxide systems.
4. Industrial Belts and Rollers
Conveyor belts, timing belts, and rollers are subjected to constant flexing and tension. Vultac helps these components resist cracking, heat buildup, and fatigue failure.
One manufacturer in Germany reported a 25% increase in belt life after reformulating with Vultac 5 and DPG. The tighter crosslink network reduced hysteresis, which in turn lowered operating temperatures — a key factor in belt longevity.
How to Use Vultac in Your Rubber Formulation
If you’re a rubber compounder or a materials engineer, you might be wondering how to incorporate Vultac into your formulations. The good news is that Vultac is easy to use and compatible with most standard rubber processing equipment.
Here’s a basic formulation guideline for a typical NR (natural rubber) compound using Vultac:
| Ingredient | Parts per Hundred Rubber (phr) | Notes |
|---|---|---|
| Natural Rubber | 100 | Base polymer |
| Carbon Black N330 | 50 | Reinforcing filler |
| Zinc Oxide | 5 | Activator |
| Stearic Acid | 2 | Processing aid |
| Antioxidant (e.g., 6PPD) | 1.5 | Protects against oxidative aging |
| Vultac 7 | 1.5–2.0 | Vulcanizing agent |
| Accelerator (e.g., CBS) | 0.5–1.0 | Controls cure rate |
| Sulfur (if needed) | 0.5–1.0 | Optional for fine-tuning crosslinking |
Curing conditions typically range from 140°C to 160°C for 20–40 minutes, depending on the thickness of the part and the desired degree of vulcanization.
Tip: For best results, optimize the accelerator system to match the Vultac compound. For example, CBS (N-cyclohexyl-2-benzothiazole sulfenamide) works well with Vultac 7, while DPG (diphenylguanidine) can be used with Vultac 55 for faster curing.
Safety and Handling
Vultac compounds are generally safe to handle, but like all chemical additives, they should be used with proper safety precautions. Here are some key points:
- Storage: Store in a cool, dry place away from direct sunlight. Shelf life varies by product but is typically 1–3 years.
- Dust Inhalation: Avoid prolonged exposure to dust. Use proper ventilation or dust masks in mixing areas.
- Skin Contact: May cause mild irritation. Wash with soap and water if contact occurs.
- Regulatory Compliance: Vultac products comply with major international regulations including REACH (EU) and TSCA (USA).
The Future of Vultac: Green Chemistry and Sustainability
As the world moves toward greener chemistry, Arkema has been proactive in developing more sustainable versions of Vultac. While the current Vultac line is already more environmentally friendly than traditional sulfur systems (due to lower sulfur emissions and reduced bloom), future formulations may include:
- Bio-based accelerators to reduce dependency on petrochemicals
- Lower-temperature curing systems to cut energy use
- Recyclable rubber compounds enhanced with Vultac for better reprocessing
In a 2022 white paper, Arkema outlined its roadmap for sustainable rubber additives, with Vultac playing a central role in enabling low-emission, high-performance rubber products.
Final Thoughts: Why Vultac Still Matters
In an age where we’re constantly chasing the next big thing — graphene, nanotubes, smart polymers — it’s easy to overlook the quiet heroes of materials science. Vultac may not be flashy, but it’s effective, reliable, and adaptable.
From the tires on your car to the seals in your airplane, Vultac is working behind the scenes to ensure that rubber stays rubber — resilient, durable, and ready for whatever life throws at it.
So the next time you zip up your boots, start your car, or open the fridge, remember: there’s a bit of Vultac in that moment of quiet confidence. And that’s no small thing.
References
- Rubber Chemistry and Technology, Vol. 89, No. 3 (2016). Crosslink Structure and Mechanical Properties of Natural Rubber Vulcanized with Sulfur Donors.
- Fraunhofer Institute for Polymer Chemistry (2021). Performance Evaluation of EPDM Seals in Automotive Applications.
- NASA Technical Memorandum TM-2018-2200. Vulcanization of Fluoroelastomers for Aerospace Seals.
- Arkema Technical Data Sheets for Vultac Series (2023).
- Journal of Applied Polymer Science, Vol. 135, Issue 18 (2018). Comparative Study of Vulcanization Systems in NR and SBR.
- European Chemicals Agency (ECHA). REACH Registration Dossier for Thiuram Disulfides.
- Rubber World, April 2022. Trends in Sustainable Rubber Additives.
- Polymer Testing, Vol. 90, 107235 (2020). Effects of Sulfur Donors on Compression Set and Aging Resistance in Rubber Seals.
💬 Got questions or want to share your experience with Vultac? Drop a comment below!
🔧 Stay tuned for our next deep dive into rubber compounding — it’s going to be elastic-ally awesome!
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