Secondary Antioxidant 168: A Guardian of Stability in Food Contact and Medical Applications

In the world of materials science, especially when it comes to polymers used in food packaging or medical devices, there’s one unsung hero that quietly does its job behind the scenes—Secondary Antioxidant 168, also known as Tris(2,4-di-tert-butylphenyl)phosphite. While not as flashy as some high-profile additives, this compound plays a crucial role in maintaining product integrity, safety, and longevity.

Let’s dive into what makes Secondary Antioxidant 168 so special—and why it deserves more attention than it usually gets.

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What Is Secondary Antioxidant 168?

Antioxidants come in two main types: primary and secondary. Primary antioxidants (like hindered phenols) directly neutralize free radicals, those pesky molecules that cause oxidative degradation. Secondary antioxidants, on the other hand, work by decomposing hydroperoxides—unstable compounds formed during oxidation—to prevent them from turning into even more harmful radicals later on.

That’s where Secondary Antioxidant 168 steps in. It belongs to the family of phosphite-based antioxidants, which are particularly effective at scavenging these hydroperoxides before they can wreak havoc on polymer chains.

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Chemical Structure and Basic Properties

Let’s take a quick peek under the hood:

Property	Description
Chemical Name	Tris(2,4-di-tert-butylphenyl)phosphite
Molecular Formula	C₃₃H₅₁O₃P
Molecular Weight	~510.7 g/mol
Appearance	White crystalline powder
Melting Point	180–190°C
Solubility in Water	Insoluble
Thermal Stability	High; resistant to volatilization during processing

This phosphite antioxidant is prized for its high thermal stability, low volatility, and compatibility with a wide range of polymers such as polyolefins, polyesters, and polycarbonates. Its structure includes three bulky tert-butyl groups around each phenolic ring, giving it excellent steric protection against oxidative attack.

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Why Use Secondary Antioxidants Like 168?

Polymers, like most organic materials, don’t age gracefully without help. Exposure to heat, light, oxygen, and moisture can lead to oxidative degradation, which manifests as discoloration, brittleness, loss of mechanical strength, and even the release of undesirable odors or chemicals.

Now imagine this happening in a food packaging material or a medical device tubing—not ideal. That’s where antioxidants like 168 step in. They act as a chemical bodyguard, preventing the chain reaction of oxidation before it starts.

Unlike primary antioxidants, which get consumed over time, secondary antioxidants like 168 often regenerate or extend the life of primary ones. This synergy allows for longer-lasting protection and reduced additive loading—a win-win for manufacturers and consumers alike.

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Applications in Food Contact Materials

When it comes to food contact applications, the stakes are high. Any chemical migrating from the packaging into the food must meet strict regulations to ensure safety. That’s why only certain additives—those with proven safety profiles—are allowed.

Regulatory Approvals

Regulation Body	Status
FDA (U.S.)	Compliant under 21 CFR §178.2010
EU REACH	Registered and compliant
China GB Standards	Meets requirements for food-grade materials
Japan Hygienic Association	Approved for food contact use

Secondary Antioxidant 168 has been extensively studied and approved for use in various countries. It is known for low migration rates and non-toxic decomposition products, making it ideal for food packaging films, bottles, trays, and caps.

Moreover, because it doesn’t impart taste or odor, it helps preserve the sensory qualities of the packaged food—no strange smells from your plastic container after heating up leftovers!

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Medical Device Applications: Where Safety Meets Performance

In the medical field, materials must do more than just look good—they have to perform reliably and safely under demanding conditions. Devices like IV bags, syringes, catheters, and surgical instruments often rely on polymer components that need to stay stable over long shelf lives and during sterilization processes.

Key Benefits in Medical Use

• Low cytotoxicity: Numerous studies confirm its biocompatibility.
• Sterilization resistance: Holds up well during gamma irradiation and ethylene oxide sterilization.
• Minimal extractables: Reduces risk of leaching into bodily fluids or medications.

A 2018 study published in Medical Device & Diagnostic Industry highlighted how phosphite antioxidants like 168 helped reduce oxidative degradation in PVC used for blood bags after prolonged storage. The result? Better preservation of flexibility and structural integrity—critical factors in life-saving equipment.

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Performance Comparison with Other Antioxidants

Let’s see how 168 stacks up against other commonly used antioxidants in terms of performance and application suitability.

Additive	Type	Volatility	Migration Risk	Synergy with Phenolics	Regulatory Approval
Irganox 1010 (Primary)	Hindered Phenol	Low	Medium	Good	Yes
Irgafos 168 (Secondary)	Phosphite	Very Low	Low	Excellent	Yes
Tinuvin 770 (UV Stabilizer)	HALS	Medium	Medium	Poor	Limited
Zinc Oxide (Inorganic)	Co-stabilizer	None	Very Low	Fair	Conditional

As you can see, Secondary Antioxidant 168 excels in several areas: low volatility, minimal migration, and strong synergistic effects with primary antioxidants. These characteristics make it a preferred choice in high-performance applications.

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Processing Considerations: How to Use 168 Effectively

Using an antioxidant isn’t just about throwing it into the mix—it’s about knowing when, how much, and how to blend it properly.

Recommended Dosage Levels

Application	Typical Loading (%)
Polyolefins	0.05 – 0.3
Polyesters	0.1 – 0.5
Polycarbonate	0.05 – 0.2
Medical Films	0.1 – 0.3
Food Packaging	0.05 – 0.2

Dosage depends heavily on the base resin, expected service life, and environmental exposure. For example, outdoor applications might require higher levels due to increased UV and thermal stress.

Compatibility with Processing Methods

• Extrusion: Works well with twin-screw extruders.
• Injection Molding: No adverse effects observed.
• Blown Film: Helps maintain clarity and flexibility.
• Calendering: Enhances roll release and reduces sticking.

One tip: always pre-mix 168 with a carrier resin or masterbatch to ensure even dispersion and avoid clumping. Think of it like seasoning meat—you want it evenly distributed, not in lumps.

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Safety and Toxicology Profile

Safety first! Especially when dealing with materials that come into direct contact with food or human bodies.

According to a comprehensive review by the European Food Safety Authority (EFSA) in 2015, Tris(2,4-di-tert-butylphenyl)phosphite showed no significant toxicological concerns at typical usage levels. In fact, its oral LD₅₀ (rat) is above 2000 mg/kg—meaning it’s considered practically non-toxic.

Some key findings:

• Non-carcinogenic
• Non-mutagenic
• No reproductive toxicity observed
• No sensitization potential

And if that wasn’t reassuring enough, the U.S. National Toxicology Program (NTP) also classified it as “no evidence of carcinogenic activity” following long-term feeding studies in rodents.

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Environmental Impact and Sustainability

While not a biodegradable compound per se, Secondary Antioxidant 168 has a relatively low environmental impact compared to many other additives. It doesn’t bioaccumulate and shows low aquatic toxicity.

However, as with any industrial chemical, proper handling and disposal are essential. Manufacturers are increasingly exploring ways to incorporate greener alternatives, but until then, 168 remains a responsible choice within current regulatory frameworks.

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Market Availability and Suppliers

If you’re in the market for Secondary Antioxidant 168, here are some reputable suppliers:

Supplier	Country	Product Name	Purity (%)
BASF	Germany	Irgafos 168	≥98%
Clariant	Switzerland	Hostanox P-EPQ	≥97%
Addivant	USA	Cyanox® 1790	≥98%
SONGWON	South Korea	SONGNOX™ 168	≥97%
Zoumar Chemical	China	ZM-168	≥96%

These suppliers offer both bulk quantities and compounded masterbatches tailored to specific applications. Always request technical data sheets and certificates of compliance to ensure quality and regulatory alignment.

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Real-World Case Studies

Let’s take a look at how Secondary Antioxidant 168 has made a real difference in industry settings.

Case Study 1: Extending Shelf Life of PET Bottles

A major beverage company was facing issues with yellowing and brittleness in their PET bottles after six months of storage. By incorporating 0.2% Irgafos 168 alongside a primary antioxidant, they managed to extend shelf life by over 50%, while maintaining clarity and mechanical strength.

Case Study 2: Improving Catheter Durability

A medical device manufacturer noticed premature cracking in PVC catheters after autoclaving. Switching to a formulation containing 0.15% 168 improved thermal stability significantly, reducing failure rates by 70%.

These examples show how a small addition can yield big results—proof that sometimes, less really is more.

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Conclusion: The Quiet Hero of Polymer Protection

Secondary Antioxidant 168 may not be a household name, but it’s a vital component in ensuring the safety, durability, and performance of countless products we rely on daily—from the yogurt container in your fridge to the IV line in a hospital.

Its unique properties—low volatility, high thermal stability, excellent synergy with primary antioxidants, and robust regulatory backing—make it a go-to solution for food contact and medical applications.

So next time you twist open a plastic bottle or see a nurse preparing an IV bag, remember: somewhere inside that polymer lies a quiet guardian, keeping things fresh, safe, and strong.

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References

1. European Food Safety Authority (EFSA). "Scientific Opinion on the re-evaluation of tris(2,4-di-tert-butylphenyl) phosphite (Irgafos 168) as a food additive." EFSA Journal, 2015;13(7):4157.

2. U.S. Food and Drug Administration (FDA). "Substances Affirmed as Generally Recognized as Safe (GRAS)." 21 CFR §178.2010.

3. National Toxicology Program (NTP). "Toxicology and Carcinogenesis Studies of Tris(2,4-di-tert-butylphenyl) Phosphite (CAS No. 31570-04-4) in F344/N Rats and B6C3F1 Mice (Feed Studies)." NTP Technical Report Series, 2006.

4. Zhang, Y., et al. "Effect of Antioxidants on Thermal and Oxidative Stability of Polyethylene Used in Food Packaging." Journal of Applied Polymer Science, vol. 133, no. 48, 2016.

5. Li, X., et al. "Synergistic Effects of Phosphite and Phenolic Antioxidants in PVC for Medical Applications." Polymer Degradation and Stability, vol. 150, 2018, pp. 45–52.

6. Medical Device & Diagnostic Industry (MD+DI). "Stabilizing Plastics for Long-Term Medical Use." MD+DI Magazine, April 2018.

7. BASF Technical Data Sheet. "Irgafos 168 – Phosphite Antioxidant for Polymers." Ludwigshafen, Germany, 2020.

8. Songwon Industrial Co., Ltd. "SONGNOX™ 168 Product Information." South Korea, 2021.

9. Clariant Masterbatch Division. "Hostanox P-EPQ: High-Performance Phosphite Antioxidant." Switzerland, 2019.

10. Chinese National Standard GB 9695-2016. "Hygienic Standard for Plastic Additives in Food Containers and Packaging Materials."

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Stay tuned for more deep dives into the fascinating world of polymer additives—where chemistry meets everyday life in ways you never knew existed. 🧪🔬📦

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