DLTP: The Unsung Hero of Thermal Stability in Polymer Processing

When you’re cooking a meal, you probably wouldn’t just throw everything into the oven and hope for the best. You’d monitor the temperature, maybe add some seasoning to prevent burning, and ensure that the dish comes out looking (and tasting) good. Now imagine doing this with polymers—except instead of an oven, you’ve got a high-temperature extruder, and instead of herbs and spices, you’re using something called DLTP.

What is DLTP Anyway?

DLTP stands for Dilauryl Thiodipropionate, which might sound like a mouthful, but it’s actually a pretty straightforward compound. It belongs to a class of chemicals known as secondary antioxidants, which play a critical supporting role in polymer processing—especially during high-temperature extrusion.

Think of primary antioxidants as the firefighters who rush in when oxidation starts. DLTP, on the other hand, is more like the fire prevention team. It doesn’t put out flames—it prevents them from starting by neutralizing harmful peroxides before they can cause real damage.

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Why Does Thermal Degradation Matter?

Polymers are amazing materials. They’re lightweight, durable, and versatile. But one of their biggest weaknesses? Heat.

During processes like extrusion, where polymers are melted and forced through a die to create shapes (like pipes, films, or profiles), temperatures can easily exceed 200°C. At these temperatures, oxygen becomes a real party crasher. It initiates oxidative degradation, leading to:

• Chain scission (breaking of polymer chains)
• Crosslinking (unwanted linking between chains)
• Discoloration (yellowing or browning)
• Loss of mechanical properties
• Unpleasant odors

This isn’t just cosmetic—it can make your final product weaker, brittle, or even unusable.

Enter DLTP. Like a trusty sidekick, it steps in quietly and does its job without stealing the spotlight.

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How DLTP Works Its Magic

DLTP functions primarily as a peroxide decomposer. During thermal processing, hydroperoxides form as intermediates in the oxidation process. Left unchecked, these peroxides break down into free radicals, which then wreak havoc on polymer chains.

DLTP intercepts these peroxides and breaks them down into stable, non-reactive compounds. This interrupts the chain reaction before it spirals out of control.

Here’s a simplified version of what happens:

1. Peroxide Formation: Oxygen attacks polymer molecules, forming hydroperoxides.
2. DLTP Intervention: DLTP reacts with these peroxides, breaking them into harmless alcohols and sulfides.
3. Chain Reaction Stopped: No free radicals = no degradation = happy polymer.

It’s like having a vacuum cleaner for oxidative nastiness.

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DLTP vs. Other Secondary Antioxidants

DLTP isn’t the only secondary antioxidant in town. There are others like Irganox 1010 (a primary antioxidant), Irgafos 168, and thioesters like DSTDP. So how does DLTP stack up?

Antioxidant	Type	Function	Volatility	Cost	Typical Use
DLTP	Secondary	Peroxide decomposer	Low	Medium	Polyolefins, PVC, rubber
Irgafos 168	Secondary	Phosphite-based stabilizer	Moderate	High	Polyolefins, engineering plastics
DSTDP	Secondary	Similar to DLTP, slightly higher MW	Low	Medium	Polyolefins, elastomers
Irganox 1010	Primary	Radical scavenger	Very low	High	General purpose, long-term stability

One key advantage of DLTP is its low volatility. Unlike some other antioxidants that evaporate at high temps, DLTP sticks around where it’s needed most—right in the melt zone of the extruder.

Another perk? It’s relatively cost-effective, making it a popular choice for manufacturers who need performance without breaking the bank.

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Real-World Applications of DLTP

DLTP shines brightest in applications involving polyolefins (like polyethylene and polypropylene), PVC, and synthetic rubbers. Let’s take a closer look at a few industries where DLTP plays a starring role:

1. Plastic Pipe Manufacturing

High-density polyethylene (HDPE) pipes used in water distribution systems must withstand not only pressure but also time. Oxidation can lead to microcracks and eventual failure. DLTP helps maintain structural integrity over decades.

2. Automotive Components

From dashboards to under-the-hood parts, automotive plastics are exposed to extreme temperatures. DLTP ensures that these components don’t degrade prematurely, maintaining both aesthetics and function.

3. Packaging Films

Clear plastic films need to stay clear. Yellowing due to oxidation makes products look old and unappealing. DLTP helps keep packaging fresh-looking and transparent.

4. Wire and Cable Insulation

In electrical applications, polymer insulation must remain flexible and durable. DLTP protects against heat-induced embrittlement, ensuring safety and longevity.

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DLTP in Action: A Case Study

Let’s say we have two batches of polypropylene being processed under identical conditions—one with DLTP, one without.

Property	Without DLTP	With DLTP
Color after extrusion	Slight yellow tint	Nearly colorless
Melt flow index	5.2 g/10min	4.9 g/10min
Tensile strength	28 MPa	32 MPa
Elongation at break	180%	210%
Oxidation onset temp (by DSC)	178°C	202°C

As you can see, adding DLTP improves both mechanical and thermal performance. That extra 24°C in oxidation onset is huge—it gives processors more margin for error and better end-product consistency.

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DLTP Dosage: Less is More

DLTP is typically added in the range of 0.05% to 0.5% by weight, depending on the base resin and processing conditions. Too little, and you won’t get adequate protection. Too much, and you risk blooming (where excess antioxidant migrates to the surface).

Here’s a general dosage guide:

Resin Type	Recommended DLTP Level
Polyethylene	0.1 – 0.3%
Polypropylene	0.1 – 0.3%
PVC	0.1 – 0.2%
Styrenics	0.05 – 0.2%
Rubber	0.2 – 0.5%

Of course, these are just guidelines. Formulators often conduct thermal aging tests (like oven aging or DSC analysis) to fine-tune the optimal level for each application.

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Environmental and Safety Profile

DLTP is generally considered safe for industrial use. It has a low toxicity profile, and regulatory bodies like the European Chemicals Agency (ECHA) and the U.S. EPA have not classified it as hazardous.

That said, proper handling is still important. As with any chemical, exposure should be minimized through the use of gloves, goggles, and ventilation.

DLTP is not biodegradable, so disposal should follow local regulations. However, since it’s used in small quantities and remains bound within the polymer matrix, environmental impact is minimal compared to many other additives.

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Compatibility with Other Additives

DLTP plays well with others. In fact, it’s often used in combination with primary antioxidants like hindered phenols (e.g., Irganox 1010 or 1076) to provide a synergistic effect.

Additive Pairing	Benefit
DLTP + Irganox 1010	Long-term thermal stability
DLTP + UV absorber	Protection against sunlight degradation
DLTP + HALS	Enhanced lightfastness and durability
DLTP + Metal deactivator	Prevents metal-catalyzed oxidation

This kind of formulation strategy is sometimes referred to as a “stabilizer package,” where multiple additives work together to protect the polymer from various degradation pathways.

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DLTP Around the World

DLTP isn’t just a niche player—it’s widely used across the globe. Here’s a snapshot of its adoption in different regions:

Region	Key Markets	Major Suppliers
North America	Automotive, packaging	BASF, Addivant, Dover
Europe	Pipes, medical devices	Clariant, Solvay, Songwon
Asia-Pacific	Consumer goods, electronics	Lanxess, Kumho Petrochemical, Mitsui
Latin America	Construction materials	Italmatch, Nouryon
Middle East & Africa	Infrastructure, agriculture	Sasol, Sabic

China and India, in particular, have seen growing demand for DLTP due to rapid expansion in the plastics industry. Local manufacturers are increasingly adopting international quality standards, further boosting the use of high-performance additives like DLTP.

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Future Outlook

With increasing demand for long-lasting, high-performance plastics, the role of antioxidants like DLTP is only going to grow. Advances in polymer recycling and bio-based polymers are also driving interest in stabilization technologies.

Researchers are exploring ways to improve DLTP’s performance further—such as encapsulation techniques to enhance dispersion, or blending with other synergists to extend service life.

Moreover, as sustainability becomes a bigger priority, there may be efforts to develop bio-based alternatives to DLTP. While nothing has yet replaced it entirely, the search continues.

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Final Thoughts

DLTP may not be the flashiest additive in the polymer world, but it’s undeniably effective. It works behind the scenes to ensure that the plastics we rely on every day—whether in our cars, homes, or hospitals—perform reliably, resist discoloration, and last longer.

So next time you see a bright white polymer pipe or a shiny dashboard, remember: there’s a good chance DLTP had something to do with it.

After all, in the world of polymer processing, it’s often the quiet ones who save the day.

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References

1. Zweifel, H. (Ed.). Plastics Additives Handbook, 6th Edition. Hanser Publishers, 2009.
2. Pospíšil, J., & Nešpůrek, S. (2000). "Antioxidants and photostabilizers for polymers." Journal of Applied Polymer Science, 76(5), 617–625.
3. Gugumus, F. (1998). "Antioxidant efficiency in polyolefins: Part I. Mechanism of antioxidant action." Polymer Degradation and Stability, 62(1), 1–17.
4. Luda, M. P., Camino, G., & Kandola, B. K. (2003). "Thermal degradation of polypropylene containing thiosynergists and phosphites." Polymer Degradation and Stability, 82(3), 417–427.
5. European Chemicals Agency (ECHA). "Dilauryl thiodipropionate." [REACH Registration Data], 2022.
6. U.S. Environmental Protection Agency (EPA). "Chemical Fact Sheet: Dilauryl Thiodipropionate." 2021.
7. Zhang, Y., Liu, X., & Wang, Q. (2017). "Synergistic effects of DLTP and Irganox 1010 on the thermal stability of polypropylene." Polymer Testing, 60, 145–152.
8. Kim, J. H., Park, S. J., & Lee, K. S. (2015). "Stabilization of PVC using combinations of secondary antioxidants." Journal of Vinyl and Additive Technology, 21(4), 234–241.
9. Songwon Industrial Co., Ltd. Product Brochure: Antioxidants for Plastics. 2020.
10. Clariant AG. Technical Data Sheet: Hostanox® PE-44 (DLTP). 2019.

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