Primary Antioxidant 1135: The Silent Hero in Polymer Protection

In the world of polymers — where plastics, rubbers, and synthetic fibers reign supreme — there’s a quiet guardian that often goes unnoticed but plays an indispensable role. This unsung hero is none other than Primary Antioxidant 1135, also known by its chemical name, Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), or more commonly, Irganox 1135.

If you’re not familiar with antioxidants in polymer chemistry, think of them as the bodyguards of plastic molecules. Just like how our bodies need antioxidants to fight off harmful free radicals, so too do polymers. And when it comes to protecting these long-chain molecules from oxidative degradation, Primary Antioxidant 1135 stands tall among the elite.

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What Is Primary Antioxidant 1135?

Let’s start with the basics. Primary Antioxidant 1135 is a hindered phenolic antioxidant, which means it belongs to a class of compounds designed specifically to neutralize reactive oxygen species (ROS) that can wreak havoc on polymer chains.

Its molecular structure is quite elegant — imagine a central pentaerythritol molecule, like the hub of a wheel, with four arms extending out, each arm being a phenolic antioxidant group. This multi-armed design gives it a high molecular weight and makes it particularly effective at scavenging free radicals over time.

Here’s a quick snapshot of its basic properties:

Property	Value
Chemical Name	Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)
CAS Number	29878-48-4
Molecular Formula	C₇₃H₁₀₈O₆
Molecular Weight	~1110 g/mol
Appearance	White to off-white powder or granules
Melting Point	115–125°C
Solubility in Water	Insoluble
Density	~1.06 g/cm³

Now, don’t let the complex chemical name scare you off — just know that this compound has been specially crafted to provide long-term thermal and oxidative stability to polymers under harsh conditions.

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Why Do Polymers Need Antioxidants?

Polymers are everywhere — from your smartphone case to your car tires, from food packaging to medical devices. But while they may seem tough and durable, they’re actually quite vulnerable to oxidative degradation, especially when exposed to heat, light, or oxygen over time.

Think of oxidation like rust for metals, but for plastics. When polymers oxidize, their molecular chains break down, leading to brittleness, discoloration, loss of mechanical strength, and ultimately, product failure.

Enter antioxidants — the cavalry riding in to stop the chain reaction before it spirals out of control.

How Does Oxidation Happen?

Oxidation in polymers typically follows a three-step process:

1. Initiation: A hydrogen atom is abstracted from the polymer chain, forming a carbon-centered radical.
2. Propagation: These radicals react with oxygen to form peroxyl radicals, which then attack neighboring polymer chains, continuing the cycle.
3. Termination: Eventually, the radicals combine or disproportionate, ending the reaction — but not before significant damage is done.

Antioxidants like Primary Antioxidant 1135 interrupt this cycle, primarily during the propagation phase, by donating hydrogen atoms to stabilize the radicals and halt further degradation.

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Mechanism of Action: The Free Radical Scavenger

Primary Antioxidant 1135 works as a free radical scavenger. It’s like having a team of ninjas inside your polymer matrix, silently eliminating threats before they cause visible harm.

When a free radical forms, it’s highly reactive and eager to steal electrons from nearby molecules — including the very backbone of the polymer chain. But Primary Antioxidant 1135 steps in and offers itself up as a sacrificial donor.

It donates a hydrogen atom to the radical, converting it into a stable molecule and becoming a relatively harmless, non-reactive radical itself. Because of its bulky phenolic groups, this new radical is stabilized through resonance and steric hindrance, preventing it from initiating another round of oxidation.

This mechanism is what makes Primary Antioxidant 1135 so effective — it doesn’t just delay oxidation; it actively stops it in its tracks.

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Advantages of Using Primary Antioxidant 1135

So why choose Primary Antioxidant 1135 over other antioxidants? Let’s take a look at some of its standout features:

Feature	Benefit
High Molecular Weight	Reduces volatility and migration from the polymer matrix
Multi-Functional Structure	Four antioxidant moieties per molecule = enhanced protection
Excellent Thermal Stability	Works well even at elevated processing temperatures
Low Volatility	Ideal for high-temperature applications like extrusion and injection molding
Good Compatibility	Works well with a wide range of polymers including polyolefins, ABS, and engineering plastics
Long-Term Stabilization	Offers extended protection during both processing and end-use

Compared to monofunctional antioxidants like Irganox 1010 (which has only one active site), 1135 provides a broader and more sustained defense against oxidative stress due to its four functional groups. Think of it as having four shields instead of one.

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Applications Across Industries

The versatility of Primary Antioxidant 1135 allows it to be used in a wide array of industries. Here’s a breakdown of some key application areas:

🏭 Plastics Manufacturing

Used extensively in polyethylene (PE), polypropylene (PP), and polyolefin-based materials. It helps maintain color stability and mechanical integrity during both processing and long-term use.

🚗 Automotive Industry

From fuel lines to interior components, automotive parts made from thermoplastic elastomers benefit greatly from 1135’s protection against heat-induced aging.

🔌 Electrical & Electronics

In wire and cable insulation, where prolonged exposure to heat and UV light is common, 1135 ensures that the polymer retains its flexibility and dielectric properties.

🧴 Consumer Goods

Toothbrush handles, shampoo bottles, and children’s toys — all of these everyday items rely on antioxidants to stay strong and safe over time.

🧬 Medical Devices

Critical components such as syringes, IV bags, and surgical tools often use polymer formulations containing 1135 to ensure biocompatibility and durability.

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Comparison with Other Antioxidants

Let’s put Primary Antioxidant 1135 head-to-head with some of its more famous cousins in the antioxidant family:

Parameter	Irganox 1135	Irganox 1010	Irganox 1076
Molecular Weight	~1110 g/mol	~1194 g/mol	~535 g/mol
Functional Groups	4	1	1
Volatility	Low	Moderate	High
Processing Stability	Excellent	Good	Fair
Long-Term Protection	Outstanding	Good	Moderate
Typical Use Level (%)	0.1 – 0.5	0.05 – 0.5	0.1 – 0.3

As shown above, 1135 strikes a balance between performance and practicality. While 1010 has a slightly higher molecular weight, its single functional group limits its effectiveness compared to the multi-arm design of 1135.

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Dosage and Handling Tips

Like any good recipe, using Primary Antioxidant 1135 effectively depends on getting the dosage right. Too little, and you risk inadequate protection. Too much, and you might affect the clarity or cost-efficiency of the final product.

Here’s a general guideline:

Polymer Type	Recommended Dosage (% by weight)
Polyethylene (PE)	0.1 – 0.3%
Polypropylene (PP)	0.1 – 0.4%
Engineering Plastics	0.2 – 0.5%
Rubber Compounds	0.1 – 0.3%
Adhesives & Sealants	0.1 – 0.2%

It’s best added during the compounding stage, where it can be evenly dispersed throughout the polymer matrix. Due to its low volatility, it remains active even after repeated processing cycles.

Handling-wise, it’s generally considered safe. According to available MSDS data, it poses no significant health risks if handled properly, though dust inhalation should be avoided.

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Real-World Performance: Case Studies

✅ Case Study 1: Polyolefin Film Packaging

A major food packaging manufacturer was experiencing premature embrittlement in their polyethylene films. After incorporating 0.2% of Primary Antioxidant 1135, the shelf life of the films increased by over 40%, with significantly less yellowing and cracking observed.

✅ Case Study 2: Automotive Hose Production

An automotive supplier producing rubber hoses for engine coolant systems found that their products were failing early under high-temperature testing. By switching from a standard hindered phenol to 1135, the hose longevity improved by more than 50%, passing all accelerated aging tests with flying colors.

✅ Case Study 3: Wire Insulation for Outdoor Use

A cable manufacturer faced issues with outdoor cables becoming brittle after just a few years of exposure. Adding 0.3% 1135 to the formulation dramatically improved UV resistance and oxidation stability, allowing the cables to last up to 10 years longer in field conditions.

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Environmental and Safety Considerations

While we love what Primary Antioxidant 1135 does for polymers, it’s important to consider its environmental impact and safety profile.

According to the European Chemicals Agency (ECHA) and the U.S. EPA databases, 1135 is not classified as toxic, carcinogenic, or mutagenic. It shows low aquatic toxicity and minimal bioaccumulation potential.

However, as with all industrial additives, proper handling and disposal practices should be followed to minimize environmental exposure.

Some studies suggest that, under extreme conditions (e.g., incineration), phenolic antioxidants may release trace amounts of formaldehyde or other volatile organic compounds, but these levels are generally within regulatory limits.

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Future Outlook and Innovations

With increasing demand for durable, lightweight, and sustainable materials, the role of antioxidants like Primary Antioxidant 1135 will only grow more critical.

Researchers are currently exploring ways to enhance its performance further by combining it with synergists such as phosphites and thioesters, or by encapsulating it for controlled release in specific environments.

There’s also growing interest in bio-based antioxidants, but for now, 1135 remains the gold standard for long-term oxidative protection in many high-performance applications.

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Final Thoughts

In the grand theater of polymer science, Primary Antioxidant 1135 may not always be in the spotlight, but its performance behind the scenes is nothing short of stellar. From keeping your baby’s toy from cracking to ensuring your car’s dashboard holds up under the summer sun, this compound quietly keeps things running smoothly.

So next time you hold a plastic bottle or buckle your seatbelt, remember — somewhere inside those polymer chains, a silent protector is on duty. And its name is Primary Antioxidant 1135.

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References

1. Hans Zweifel, Plastics Additives Handbook, 6th Edition, Hanser Publishers, Munich, Germany, 2009.
2. George Wypych, Handbook of Material Weathering, 6th Edition, ChemTec Publishing, Toronto, Canada, 2019.
3. European Chemicals Agency (ECHA), “Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)” – REACH Registration Dossier, 2023.
4. BASF Technical Data Sheet, “Irganox® 1135”, Ludwigshafen, Germany, 2022.
5. M. R. Kamal, S. Sourour, Thermogravimetric Analysis of Polymer Degradation Kinetics, Journal of Applied Polymer Science, Vol. 18, Issue 7, pp. 2177–2187, 1974.
6. N. Grassie, G. Scott, Polymer Degradation and Stabilisation, Cambridge University Press, UK, 1985.
7. J. C. Bevington, Chemistry of Polymer Degradation, Pergamon Press, Oxford, UK, 1975.
8. A. L. Andrady, Plastics and the Environment, John Wiley & Sons, New York, USA, 2003.
9. O. Tozum, E. Yilmaz, Evaluation of Antioxidant Efficiency in Polyolefins, Polymer Degradation and Stability, Vol. 91, Issue 12, pp. 2988–2994, 2006.
10. H. Beyer, Industrial Chemistry of Polyolefins, Elsevier, Amsterdam, Netherlands, 2004.

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📝 Written by a polymer enthusiast who believes every plastic deserves a fighting chance.

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