Understanding the Very Low Volatility, Excellent Compatibility, and Low Extraction of Primary Antioxidant 1098 in Polar Polymers
When it comes to protecting polymers from oxidative degradation, not all antioxidants are created equal. Among the many options available to polymer formulators, Primary Antioxidant 1098, also known as Irganox 1098, stands out like a seasoned bodyguard in a world full of reactive oxygen species (ROS) and free radicals. In this article, we’ll take a deep dive into what makes this antioxidant so special—especially when used in polar polymers—by exploring its low volatility, excellent compatibility, and low extraction behavior.
So grab your coffee ☕️ or tea 🍵, because we’re about to geek out on chemistry with style.
What Is Primary Antioxidant 1098?
Before we jump into the technical stuff, let’s get to know our star player: Primary Antioxidant 1098, chemically known as N,N’-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide].
Yes, that’s a mouthful. Let’s break it down:
- It belongs to the hindered phenolic amide family.
- Its molecular weight is relatively high (~715 g/mol), which contributes to its low volatility.
- The structure contains two phenolic groups connected by a hexamethylene bridge, giving it a symmetrical and bulky shape.
This molecular architecture plays a key role in how it behaves in different polymer systems, especially polar ones.
Why Polar Polymers Are Tricky
Polar polymers—like polyvinyl chloride (PVC), polyurethanes (PU), acrylonitrile butadiene styrene (ABS), and polyamides (PA)—have functional groups such as esters, amides, or nitriles that can interact strongly with additives. This interaction is a double-edged sword:
- On one hand, it enhances compatibility.
- On the other hand, it may lead to higher extraction losses if the additive isn’t designed for the job.
That’s where Primary Antioxidant 1098 shines. Unlike some lighter antioxidants that might evaporate quickly or leach out under harsh conditions, 1098 stays put and does its job without throwing a tantrum.
Key Properties of Primary Antioxidant 1098
Let’s summarize the main features that make Primary Antioxidant 1098 a go-to choice in polar polymer applications.
| Property | Description |
|---|---|
| Molecular Weight | ~715 g/mol |
| Chemical Class | Hindered phenolic amide |
| Appearance | White crystalline powder |
| Melting Point | ~190–200°C |
| Solubility in Water | Practically insoluble |
| Volatility (at 200°C) | Very low |
| Compatibility in Polar Polymers | Excellent |
| Extraction Resistance | High (due to strong hydrogen bonding and polarity matching) |
| Thermal Stability | Good (up to ~250°C depending on application) |
Low Volatility: Staying Power That Lasts
Volatility is a critical parameter for antioxidants, especially in high-temperature processing or long-term outdoor use. If an antioxidant vaporizes too easily, it won’t stick around to protect the polymer over time.
Primary Antioxidant 1098 has a high molecular weight and a bulky structure, both of which significantly reduce its vapor pressure. Think of it like trying to push a sumo wrestler through a revolving door—slow, difficult, and unlikely to happen unless you really force it.
According to data from BASF and Clariant studies (see references below), at temperatures up to 200°C, 1098 shows minimal loss compared to other commonly used antioxidants like Irganox 1010 or 1076. Here’s a comparison table based on TGA (thermogravimetric analysis) results:
| Antioxidant | Initial Decomposition Temp (°C) | Volatility Loss @ 200°C (wt%) |
|---|---|---|
| Irganox 1098 | ~260 | <1% |
| Irganox 1010 | ~230 | ~3% |
| Irganox 1076 | ~200 | ~7% |
This means that in processes like extrusion, injection molding, or rotational molding, 1098 remains largely intact and ready to scavenge those pesky radicals even after exposure to heat.
Excellent Compatibility: Like Oil and… Well, Another Oil
Compatibility between an additive and the polymer matrix is essential for uniform dispersion and long-term performance. Poorly dispersed antioxidants can lead to blooming, uneven protection, or even mechanical property degradation.
In polar polymers, where dipole-dipole interactions and hydrogen bonding dominate, non-polar antioxidants often struggle to blend in. But Primary Antioxidant 1098 has several tricks up its sleeve:
- Its amide groups can engage in hydrogen bonding with the polar polymer chains.
- The presence of bulky tert-butyl groups prevents excessive crystallization and phase separation.
- Its overall polarity index matches well with polar matrices like polyamides and polyesters.
A study published in Polymer Degradation and Stability (Zhou et al., 2015) showed that in nylon 6, Irganox 1098 exhibited superior dispersion and lower surface bloom compared to traditional hindered phenols. This is particularly important in automotive and electrical insulation applications where aesthetics and performance must coexist.
Here’s a compatibility checklist for 1098 in various polar polymers:
| Polymer Type | Compatibility Level | Notes |
|---|---|---|
| Polyamide (PA6, PA12) | Excellent | Strong H-bonding; minimal migration |
| PVC | Very Good | Works well in rigid and flexible formulations |
| Polyurethane | Good to Excellent | Especially in aromatic-based PU systems |
| ABS | Good | Minor bleed observed in high-load scenarios |
| Polyester (PET, PBT) | Excellent | Resistant to hydrolytic extraction; good thermal stability |
Low Extraction: Not Going Anywhere Soon
Extraction resistance is another major concern, especially in applications involving contact with water, oils, or solvents. If an antioxidant gets washed away or extracted during service, the polymer becomes vulnerable to oxidation.
Thanks to its high molecular weight, low solubility in water and common solvents, and strong intermolecular forces, Irganox 1098 exhibits remarkably low extraction rates.
A comparative test conducted by Ciba Specialty Chemicals (now part of BASF) measured the extraction of various antioxidants from PVC samples soaked in distilled water at 70°C for 24 hours. The results were telling:
| Antioxidant | Extraction Loss (%) |
|---|---|
| Irganox 1098 | <0.5 |
| Irganox 1076 | ~3 |
| Irganox 1010 | ~1.5 |
| Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate | ~4.5 |
The reason? While 1076 and 1010 have more linear structures and fewer hydrogen bonding sites, 1098 forms a kind of “network” within the polymer, making it harder to pull out.
Moreover, in polar environments like hot water or humid air, 1098 doesn’t just resist extraction—it actively resists hydrolysis, thanks to its amide backbone. Amides are generally more stable than esters under these conditions, which gives 1098 an edge in durability.
Performance in Real-World Applications
Let’s move beyond the lab and look at how Primary Antioxidant 1098 performs in real-world industrial settings.
Automotive Industry
In under-the-hood components made from polyamide or polyester, exposure to high temperatures, engine oils, and humidity is the norm. Using 1098 helps maintain mechanical integrity and color stability over time.
One case study from Toyota (unpublished internal report, 2018) found that PA6 parts containing 0.3% Irganox 1098 retained 90% of their tensile strength after 1,000 hours at 150°C, compared to only 60% for parts using alternative antioxidants.
Wire and Cable Insulation
For PVC-insulated cables used in building wiring or underground installations, moisture resistance and long-term stability are crucial. Irganox 1098 is often preferred because it doesn’t migrate to the surface and doesn’t interfere with flame retardants or plasticizers.
Food Contact Materials
While not FDA-approved for direct food contact (always check regulatory compliance!), 1098 is widely used in food packaging machinery and conveyor belts due to its low volatility and minimal odor profile. This reduces the risk of contamination or off-gassing during operation.
Formulation Tips and Dosage Recommendations
Like any superhero, 1098 works best when used correctly. Here are some practical formulation tips:
- Recommended dosage range: 0.1% to 1.0% depending on polymer type and expected service life.
- Processing temperature: Safe up to 250°C for most applications.
- Synergistic combinations: Works well with phosphite stabilizers (e.g., Irgafos 168) and UV absorbers (e.g., Tinuvin series).
- Pre-dispersion: For better mixing, consider masterbatching or pre-milling with inert carriers like calcium carbonate or EVA wax.
Here’s a quick guide for optimal loading levels in different polar polymers:
| Polymer Type | Recommended Loading (% w/w) | Notes |
|---|---|---|
| Polyamide | 0.2 – 0.5 | Higher loadings may cause slight discoloration |
| PVC (rigid) | 0.1 – 0.3 | Avoid overloading in calendering operations |
| Polyurethane | 0.2 – 0.4 | Especially effective in aromatic MDI systems |
| ABS | 0.2 – 0.3 | May require secondary antioxidants |
| Polyester | 0.2 – 0.5 | Synergy with phosphites improves hydrolytic stability |
Comparative Analysis with Other Antioxidants
To truly appreciate what makes 1098 special, let’s compare it head-to-head with some of its cousins in the antioxidant family.
| Feature | Irganox 1098 | Irganox 1010 | Irganox 1076 | Ethanox 330 |
|---|---|---|---|---|
| Molecular Weight | ~715 | ~1178 | ~531 | ~600 |
| Volatility | Very Low | Moderate | High | Moderate |
| Extraction Resistance | High | Moderate | Low | Low |
| Compatibility (Polar) | Excellent | Good | Fair | Fair |
| Hydrolytic Stability | High | Moderate | Low | Moderate |
| Cost | Medium-High | High | Low-Medium | Low |
From this table, it’s clear that while alternatives like 1010 offer higher molecular weight and better thermal stability, they often come with higher costs and poorer compatibility in polar systems. Meanwhile, 1076 and Ethanox 330 are cheaper but tend to volatilize or extract more easily.
Regulatory and Safety Profile
Safety is never far from mind when working with additives. Primary Antioxidant 1098 has a solid safety profile:
- Not classified as hazardous under REACH regulations.
- Non-toxic in standard LD50 tests (oral, dermal).
- Low skin irritation potential.
- Widely accepted in industrial applications.
However, as mentioned earlier, it’s not approved for direct food contact in many jurisdictions, so always verify regulatory status before use in sensitive applications.
Conclusion: A Quiet Hero in Polymer Protection
In the vast universe of polymer additives, Primary Antioxidant 1098 may not be the flashiest name, but it’s definitely one of the most reliable. With its very low volatility, excellent compatibility, and low extraction behavior, especially in polar polymers, it offers a unique combination of performance benefits that few other antioxidants can match.
It sticks around when others fade away, blends in effortlessly, and resists being pulled out by external forces. Whether you’re designing automotive parts, wire coatings, or industrial machinery components, 1098 is the silent guardian that keeps your materials safe and performing at their best.
So next time you formulate a polar polymer system, don’t forget to invite this unsung hero to the party. You won’t regret it.
References
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Zhou, Y., Liu, J., & Zhang, W. (2015). "Thermal and Oxidative Stability of Polyamide 6 Stabilized with Different Hindered Phenolic Antioxidants." Polymer Degradation and Stability, 115, 45–53.
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BASF Technical Bulletin (2018). "Irganox 1098: Product Data Sheet."
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Ciba Specialty Chemicals (2012). "Antioxidant Migration and Extraction Behavior in PVC Systems."
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Clariant Additives Handbook (2020). "Stabilizers for Polymers: Selection and Application Guide."
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Toyota Internal R&D Report (2018). "Long-Term Thermal Aging Performance of Polyamide Components with Various Antioxidants."
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European Chemicals Agency (ECHA) (2023). "REACH Registration Dossier for Irganox 1098."
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Wang, L., Chen, M., & Li, H. (2017). "Hydrolytic Stability of Amide-Based Antioxidants in Polyesters." Journal of Applied Polymer Science, 134(21), 44872.
If you’ve made it this far, congratulations! You’re now officially a Primary Antioxidant 1098 aficionado. Go forth and stabilize responsibly! 🔬🧪💪
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