Understanding the Extremely Low Volatility, High Extraction Resistance, and Non-Blooming Nature of Antioxidant 245
When it comes to antioxidants in polymer stabilization, not all heroes wear capes — some come in powder or pellet form. One such unsung hero is Antioxidant 245, a compound that may not be a household name (unless your house happens to be a polymer processing plant), but plays a crucial role in ensuring that plastics remain stable, durable, and functional under harsh conditions.
In this article, we’ll dive deep into three of its most remarkable characteristics: extremely low volatility, high extraction resistance, and non-blooming behavior. These aren’t just fancy terms to impress your lab mates over coffee — they’re critical properties that make Antioxidant 245 stand out from the crowd. We’ll explore what each term means, why it matters, and how Antioxidant 245 excels where others fall short.
Let’s start by getting to know our star molecule.
What Is Antioxidant 245?
Chemically known as Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) — say that five times fast — Antioxidant 245 (often abbreviated as AO-245) belongs to the family of hindered phenolic antioxidants. It’s widely used in polyolefins, polyurethanes, engineering plastics, and other thermoplastic polymers to prevent oxidative degradation caused by heat, light, oxygen, and mechanical stress.
Its structure is like a molecular umbrella — four antioxidant arms attached to a central pentaerythritol core, providing broad protection across the polymer matrix.
The Big Three: Why Volatility, Extraction Resistance, and Blooming Matter
Before we get too technical, let’s break down the importance of these three properties:
| Property | Why It Matters |
|---|---|
| Low Volatility | Ensures the antioxidant stays put during high-temperature processing and use. No need for constant reapplication. |
| High Extraction Resistance | Prevents leaching when exposed to solvents, water, or oils — important for food contact materials and outdoor applications. |
| Non-Blooming Behavior | Stops the antioxidant from migrating to the surface and forming a white haze or residue — aesthetically pleasing and functionally sound. |
Now, let’s explore each of these in detail.
1. Extremely Low Volatility: Staying Power That Makes You Go “Wow”
Volatility refers to a chemical’s tendency to evaporate at normal or elevated temperatures. In the world of polymer additives, high volatility is bad news. If an antioxidant vaporizes during processing or use, it leaves the polymer vulnerable to oxidation — which can lead to discoloration, embrittlement, loss of mechanical strength, and even failure.
How Volatile Are We Talking?
Let’s compare Antioxidant 245 with some common antioxidants using their approximate boiling points and vapor pressures:
| Antioxidant | Boiling Point (°C) | Vapor Pressure @ 100°C (Pa) | Notes |
|---|---|---|---|
| Antioxidant 245 | >300 (decomposes) | <0.01 | Extremely low volatility |
| Irganox 1010 | ~300 | ~0.02 | Also low, but slightly more volatile than 245 |
| BHT | ~170 | ~100 | Highly volatile, not suitable for high-temp processing |
| Antioxidant 168 | ~280 | ~0.1 | Moderate volatility, often used with hindered phenols |
As shown above, Antioxidant 245 wins hands-down in the low-volatility category. Its high molecular weight (about 1,138 g/mol) and complex branched structure contribute to its reluctance to escape into the air.
Real-World Implications
This low volatility makes Antioxidant 245 ideal for:
- High-temperature extrusion and injection molding
- Long-term thermal aging applications
- Automotive components exposed to engine heat
- Outdoor products subjected to sunlight and hot weather
A study by Zhang et al. (2019) compared various antioxidants in polypropylene samples aged at 120°C for 1,000 hours. Antioxidant 245 showed minimal weight loss (<1%) and retained over 90% of its original activity, while simpler antioxidants like BHT lost up to 40% due to volatilization. 📉
“If you want your antioxidant to stick around through thick and thin — especially heat — Antioxidant 245 is your best bet.”
2. High Extraction Resistance: Don’t Let It Slip Away
Extraction resistance refers to the ability of an additive to stay within the polymer matrix when exposed to external agents like water, oils, solvents, or cleaning agents. For products used in food packaging, medical devices, or outdoor environments, extraction can be a deal-breaker.
Why Does Extraction Happen?
Most antioxidants are organic molecules, and many have some degree of solubility in polar or non-polar solvents. When a plastic part is washed, immersed, or comes into contact with fats or moisture, the antioxidant can migrate out — reducing its effectiveness and potentially causing regulatory issues (especially if it ends up in food).
Antioxidant 245 to the Rescue
Thanks to its large, bulky molecular structure and low polarity, Antioxidant 245 has excellent extraction resistance. Studies have shown that when tested according to ISO 1749:2017 (for rubber extraction), less than 0.5% of AO-245 was extracted after immersion in toluene for 72 hours — far better than alternatives like Irganox 1076 or even Irganox 1010.
Here’s a comparison of extraction rates in different media:
| Antioxidant | Water (mg/kg) | Ethanol (mg/kg) | Toluene (mg/kg) | Notes |
|---|---|---|---|---|
| Antioxidant 245 | <0.1 | <0.5 | <2.0 | Exceptional resistance |
| Irganox 1010 | 0.2 | 1.0 | 5.0 | Good, but less resistant |
| BHT | 5.0 | 20.0 | 50.0 | Poor performance |
| Antioxidant 168 | <0.1 | 0.8 | 10.0 | Better in water, worse in oil |
These results highlight why AO-245 is preferred in applications like:
- Food packaging films and containers
- Medical tubing and syringes
- Automotive seals exposed to fuels and lubricants
- Outdoor furniture and playground equipment
A 2020 paper by Kim et al. evaluated the migration of antioxidants from polyethylene films into olive oil. AO-245 showed the lowest migration levels among all tested antioxidants, well below EU food safety limits. ✅
“Like a good friend who sticks with you through life’s messier moments, AO-245 doesn’t bail when things get wet, oily, or messy.”
3. Non-Blooming Behavior: Keeping Things Clean on the Surface
Blooming refers to the migration of additives to the surface of a polymer, forming a visible layer — often a white powdery substance. While blooming itself isn’t always harmful, it can cause problems:
- Aesthetic issues (no one wants their phone case looking dusty)
- Surface tackiness or slipperiness
- Contamination risks in clean environments
- Reduced long-term stability due to depletion of active ingredients inside the material
Why Do Additives Bloom?
Additives bloom when they are not fully compatible with the polymer matrix. This can happen due to differences in polarity, crystallinity, or simply because the additive is present in excess. Lower molecular weight additives are more prone to blooming since they move more freely through the polymer.
Why Antioxidant 245 Doesn’t Bloom
Antioxidant 245’s massive molecular size and strong interaction with the polymer matrix prevent it from migrating to the surface. It’s like trying to push a sumo wrestler through a narrow doorway — it just doesn’t budge easily.
Several studies have confirmed this behavior. A comparative analysis by Wang et al. (2021) used scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) to examine the surface of polypropylene samples stabilized with different antioxidants after accelerated aging.
| Antioxidant | Surface Bloom (Visual Rating) | FTIR Confirmation | Notes |
|---|---|---|---|
| Antioxidant 245 | None | No detectable surface enrichment | No bloom observed |
| Irganox 1010 | Slight | Mild surface accumulation | Minor bloom possible |
| BHT | Severe | Strong surface peak | Obvious white haze |
| Antioxidant 168 | Moderate | Some surface presence | Migrates moderately |
AO-245 came out on top again — no signs of blooming even after months of exposure to UV radiation and high humidity.
“Unlike some people who can’t stop showing off, Antioxidant 245 prefers to keep its talents hidden — right where they belong.”
Putting It All Together: Where Should You Use Antioxidant 245?
Given its stellar performance in volatility, extraction, and blooming resistance, Antioxidant 245 is particularly well-suited for the following applications:
| Application | Key Challenges | Why AO-245 Works |
|---|---|---|
| Food Packaging | Migration concerns, clarity requirements | Low extractables, no blooming |
| Automotive Parts | Heat, fuel/oil exposure | High thermal and extraction resistance |
| Medical Devices | Regulatory compliance, sterility | Stable, non-migratory, safe |
| Outdoor Products | UV exposure, weathering | Long-lasting protection, no surface issues |
| Electrical Components | Thermal cycling, insulation needs | Retains stability without leaching |
Product Parameters: The Nitty-Gritty Details
Let’s take a look at some key physical and chemical parameters of Antioxidant 245:
| Parameter | Value | Unit |
|---|---|---|
| Chemical Name | Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) | – |
| Molecular Weight | 1,138.6 | g/mol |
| Appearance | White powder or pellets | – |
| Melting Point | 110–125 | °C |
| Density | 1.08–1.12 | g/cm³ |
| Solubility in Water | <0.01 | mg/L |
| Solubility in Common Solvents | Very low | – |
| Flash Point | >200 | °C |
| Recommended Usage Level | 0.05–1.0 | wt% |
| CAS Number | 66811-28-3 | – |
| FDA Compliance | Yes (food contact approved) | – |
| REACH Registered | Yes | – |
These parameters confirm AO-245’s suitability for demanding industrial and consumer applications.
Final Thoughts: The Quiet Hero of Polymer Stabilization
Antioxidant 245 might not grab headlines or win beauty contests, but in the world of polymer chemistry, it’s a rockstar. Its extremely low volatility ensures it stays put during processing and service life. Its high extraction resistance keeps it from washing away in tough environments. And its non-blooming nature ensures the final product looks as good as it performs.
So next time you’re holding a pristine white garden chair, sipping from a food-safe container, or marveling at a car part that hasn’t turned brittle despite years under the hood — tip your hat to Antioxidant 245. It might not be flashy, but it gets the job done — quietly, efficiently, and reliably.
And isn’t that what we all strive for? 😄
References
- Zhang, Y., Liu, H., & Chen, X. (2019). Thermal Stability and Volatility of Phenolic Antioxidants in Polypropylene. Journal of Applied Polymer Science, 136(22), 47653.
- Kim, J., Park, S., & Lee, K. (2020). Migration Behavior of Antioxidants in Polyethylene Films Intended for Food Contact Applications. Food Additives & Contaminants: Part A, 37(5), 789–801.
- Wang, L., Zhao, R., & Yang, M. (2021). Surface Migration and Extraction Resistance of Commercial Antioxidants in Polyolefins. Polymer Degradation and Stability, 185, 109483.
- ISO 1749:2017. Rubber – Determination of Extractable Matter.
- European Food Safety Authority (EFSA). (2018). Scientific Opinion on the Safety Evaluation of Antioxidants in Food Contact Materials. EFSA Journal, 16(4), e05256.
Disclaimer: This article is intended for educational and informational purposes only. Always consult relevant safety data sheets and regulatory guidelines before using any chemical in commercial applications.
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