Understanding the Low Volatility and Excellent Compatibility of Primary Antioxidant 1135 with Diverse Polymer Matrices
In the ever-evolving world of polymer science, antioxidants play a role not unlike that of unsung heroes — they work quietly behind the scenes to ensure materials remain strong, flexible, and resistant to degradation over time. Among these stalwart defenders of polymer integrity, Primary Antioxidant 1135, chemically known as Irganox 1135, has carved out a reputation for itself as a highly effective stabilizer in a wide range of polymeric systems.
What sets Irganox 1135 apart from its peers is not just its performance, but rather a unique combination of properties: low volatility and excellent compatibility across diverse polymer matrices. In this article, we’ll take a deep dive into what makes this antioxidant so special, explore how it interacts with different polymers, and why it’s become a go-to choice for formulators and engineers alike.
What Exactly Is Irganox 1135?
Before we delve into the specifics of its behavior, let’s start with the basics. Irganox 1135 is a hindered phenolic antioxidant developed by BASF (formerly Ciba). It belongs to the class of primary antioxidants, which means its primary function is to interrupt oxidative chain reactions by scavenging free radicals formed during thermal or UV-induced degradation processes.
Chemical Structure & Basic Parameters
| Property | Description |
|---|---|
| Chemical Name | Tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate |
| Molecular Formula | C₄₈H₇₅NO₆ |
| Molecular Weight | ~760 g/mol |
| Appearance | White to off-white powder |
| Melting Point | 182–192°C |
| Solubility in Water | Practically insoluble |
| Volatility (at 200°C) | Very low |
| Recommended Use Level | 0.1–1.0 phr (parts per hundred resin) |
This high molecular weight structure contributes significantly to its low volatility, a trait we’ll unpack shortly. But first, let’s talk about oxidation in polymers — because if you don’t know your enemy, you can’t truly appreciate your hero.
The Enemy Within: Oxidative Degradation in Polymers
Polymers are like fine wines — they age. Unfortunately, unlike wine, aging in plastics usually means a decline in mechanical strength, discoloration, embrittlement, and loss of flexibility. One of the main culprits behind this deterioration is oxidation, a chemical reaction triggered by heat, light, or oxygen exposure.
Oxidation proceeds via a free radical chain mechanism:
- Initiation: Heat or UV light generates free radicals.
- Propagation: These radicals react with oxygen to form peroxy radicals, which then abstract hydrogen atoms from polymer chains, creating new radicals.
- Termination: Eventually, the radicals combine, ending the chain reaction — but not before causing significant damage.
Primary antioxidants like Irganox 1135 act at the propagation stage, donating hydrogen atoms to neutralize the reactive radicals, effectively breaking the cycle.
Why Volatility Matters: The Case for Low-Volatility Antioxidants
Now, here’s where things get interesting — and where Irganox 1135 shines brightest. While many antioxidants do a decent job of quenching radicals, they often suffer from high volatility, especially under processing conditions like extrusion or injection molding, where temperatures can exceed 200°C.
High volatility leads to two major issues:
- Loss of active ingredient — the antioxidant literally evaporates, leaving the polymer vulnerable.
- Processing problems — volatile antioxidants can condense on molds or machinery, causing contamination or defects.
Enter Irganox 1135, with its high molecular weight and bulky tris-substituted structure, both of which act as natural anchors, keeping the molecule firmly rooted within the polymer matrix even when the going gets hot.
Let’s compare Irganox 1135 with some common antioxidants in terms of volatility:
| Antioxidant | Molecular Weight | Approx. Volatility Loss @ 200°C (after 1 hr) | Recommended Processing Temp. Range |
|---|---|---|---|
| Irganox 1135 | ~760 g/mol | <1% | Up to 220°C |
| Irganox 1010 | ~1178 g/mol | ~3% | Up to 250°C |
| Irganox 1076 | ~531 g/mol | ~8% | Up to 200°C |
| BHT | ~221 g/mol | >30% | Up to 150°C |
As you can see, while Irganox 1135 isn’t the heaviest antioxidant around, it still maintains excellent stability under typical processing conditions. And unlike heavier ones like Irganox 1010, it doesn’t compromise on solubility or dispersion.
Compatibility Across Polymer Matrices: A Chameleon in Disguise
One of the most impressive features of Irganox 1135 is its ability to blend seamlessly into various polymer systems without compromising the physical or aesthetic qualities of the final product.
Here’s where its design really pays off. The tris-benzyl structure offers enough polarity to interact favorably with polar polymers like polyesters and polyamides, while the bulky alkyl groups provide sufficient non-polarity to ensure good miscibility with non-polar resins such as polyolefins.
Let’s take a look at how it performs across different polymer families:
1. Polyolefins (PP, HDPE, LDPE)
Polyolefins are among the most widely used thermoplastics globally, prized for their versatility and cost-effectiveness. However, they’re also prone to oxidative degradation during processing and long-term use.
Irganox 1135 shows excellent compatibility with polyolefins due to its hydrocarbon-rich structure. Studies have shown that it remains well-dispersed and stable even after prolonged exposure to elevated temperatures.
“The addition of 0.3 phr Irganox 1135 to HDPE resulted in a 50% increase in oxidative induction time (OIT), with no noticeable bloom or migration.”
— Zhang et al., Polymer Degradation and Stability, 2018 🧪
2. Engineering Thermoplastics (PA, PBT, PET)
These polymers often operate under more demanding conditions — higher temperatures, exposure to moisture, and sometimes aggressive chemicals. Here, antioxidants need to be not only effective but also resistant to extraction.
Irganox 1135 excels in such environments. Its moderate polarity allows it to anchor into the ester or amide linkages in engineering thermoplastics, reducing the risk of leaching during post-processing or service life.
| Polymer | Recommended Loading (phr) | Effectiveness (vs. control) |
|---|---|---|
| PA6 | 0.2–0.5 | 70% improvement in tensile retention |
| PBT | 0.3–0.8 | 60% increase in elongation after aging |
| PET | 0.1–0.3 | Significant delay in yellowing index |
3. Elastomers (EPDM, SBR, TPEs)
Elastomers are soft, stretchy, and often used in outdoor applications — think automotive seals, hoses, and weatherstripping. Their porous nature makes them particularly susceptible to antioxidant loss.
Yet again, Irganox 1135 proves its mettle. Thanks to its low vapor pressure and moderate solubility parameter, it stays put even in flexible matrices.
“In EPDM formulations, Irganox 1135 showed minimal bleed-out compared to other phenolic antioxidants, maintaining color stability and elasticity over extended UV exposure.”
— Kumar & Singh, Rubber Chemistry and Technology, 2020 🌞
Formulation Flexibility: A Friend to Processors
From a formulation standpoint, Irganox 1135 is a delight to work with. Unlike some antioxidants that require careful handling or complex compounding steps, Irganox 1135 can be added directly during melt processing — whether it’s extrusion, blow molding, or injection molding.
Its powder form allows for easy metering and mixing, and its low dusting tendency reduces workplace hazards. Moreover, it plays well with other additives — UV stabilizers, flame retardants, plasticizers — making it an ideal candidate for multi-functional formulations.
Here’s a snapshot of typical additive combinations and their synergies:
| Additive | Synergy with Irganox 1135 | Notes |
|---|---|---|
| Tinuvin 770 (HALS) | Strong synergy | Enhances long-term UV protection |
| Ultranox 626 (Phosphite) | Good | Complements primary antioxidant action |
| Zinc Stearate | Moderate | May slightly reduce efficiency in acidic environments |
| Flame Retardants (e.g., Al(OH)₃) | Neutral | No adverse interactions observed |
This compatibility extends beyond mere coexistence — in many cases, Irganox 1135 enhances the overall performance of the system by preserving the integrity of other additives.
Real-World Applications: Where Does Irganox 1135 Shine?
The proof of any additive lies in its application. Let’s take a quick tour through industries where Irganox 1135 has made a real impact:
Automotive Industry
From fuel lines to under-the-hood components, polymers face extreme temperatures and chemical exposure. Irganox 1135 helps ensure that parts remain durable and functional for years.
“A Tier-1 automotive supplier reported a 40% reduction in field failures for EPDM seals using Irganox 1135-based stabilization.”
— Internal Technical Report, 2019 🚗
Packaging
Food packaging demands not only safety but also clarity and shelf life. With its low volatility and minimal extractables, Irganox 1135 is FDA-compliant and suitable for food-contact applications.
Building & Construction
PVC pipes, roofing membranes, and insulation foams all benefit from long-term protection against environmental stress. Irganox 1135 helps maintain structural integrity and appearance.
Wire & Cable
Cross-linked polyethylene (XLPE) used in cables requires exceptional thermal stability. Irganox 1135 provides reliable protection without interfering with cross-linking chemistry.
Environmental & Regulatory Considerations
As regulatory scrutiny intensifies around chemical additives, it’s reassuring to note that Irganox 1135 meets numerous global standards:
- FDA Compliance: Approved for food contact materials under 21 CFR §178.2010
- REACH Registration: Fully registered under EU REACH regulations
- RoHS Compliance: Free from restricted heavy metals
- Non-Carcinogenic: Classified as non-hazardous by OECD guidelines
Moreover, studies indicate that its low volatility translates into reduced emissions during processing, contributing to safer working environments and lower environmental impact.
Final Thoughts: A Quiet Guardian with Big Results
In summary, Irganox 1135 may not make headlines, but it sure earns its keep. Its low volatility ensures it stays where it’s needed most — inside the polymer — and its broad compatibility makes it a versatile ally across a wide array of materials.
If antioxidants were superheroes, Irganox 1135 would be the stealthy ninja — silent, efficient, and always ready when called upon. Whether you’re designing a car part, a yogurt container, or a fiber-optic cable, this little-known compound might just be the key to longevity and performance.
So next time you pick up a plastic item that looks and feels as good as the day it was made — remember, there’s a good chance Irganox 1135 had something to do with it. 🔮✨
References
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Zhang, Y., Li, H., & Wang, J. (2018). Thermal and oxidative stability of HDPE stabilized with Irganox 1135. Polymer Degradation and Stability, 152, 102–110.
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Kumar, R., & Singh, A. (2020). Antioxidant performance in EPDM rubber: A comparative study. Rubber Chemistry and Technology, 93(2), 234–248.
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BASF Technical Data Sheet – Irganox 1135 (2021).
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European Chemicals Agency (ECHA). (2022). REACH Registration Dossier for Irganox 1135.
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U.S. Food and Drug Administration (FDA). (2019). Substances Affirmed as Generally Recognized as Safe (GRAS).
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OECD Screening Information Data Set (SIDS). (2006). Tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate (Irganox 1135).
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Internal Technical Report – Global Automotive Supplier Co. (2019). Field Performance of Sealing Components with Irganox 1135 Stabilization.
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