A Comparative Study of Triethanolamine (TEA) as a Co-reactant and Catalyst in Polyurethane Systems
By Dr. Lin Wei – Polymer Chemist & Caffeine Enthusiast ☕
Let’s talk about triethanolamine—yes, that compound with the name so long it makes your tongue trip over itself. Triethanolamine, or TEA for short (because even chemists get tired of saying it), is like the Swiss Army knife of polyurethane chemistry: it can be a co-reactant, a catalyst, and occasionally, a mood stabilizer when your reaction tank foams like a shaken soda can. 🍼💥
In this article, we’ll peel back the layers of TEA’s multifaceted role in polyurethane (PU) systems—how it behaves when it’s just helping the reaction along (catalyst mode), and how it jumps into the fray, becoming part of the polymer backbone (co-reactant mode). We’ll compare performance, kinetics, mechanical properties, and even throw in a few cautionary tales from the lab. Think of this as TEA’s origin story—part chemistry, part drama, all science.
1. The Dual Life of TEA: Jekyll and Hyde in a Beaker
TEA wears two hats in PU systems:
- As a catalyst: It speeds up the isocyanate-hydroxyl reaction (the main event in PU formation) without becoming part of the final polymer.
- As a co-reactant: It reacts with isocyanates, becoming a crosslinking node—essentially getting married to the polymer chain.
It’s like the difference between a DJ at a wedding (catalyst) and an actual groom (co-reactant). One sets the mood, the other changes the family tree.
2. Chemical Background: Who Is TEA, Really?
Triethanolamine (C₆H₁₅NO₃) is a tertiary amine with three hydroxyl (-OH) groups. Its structure looks like a nitrogen atom holding hands with three ethanol arms. This trifecta of OH groups makes it hydrophilic, reactive, and slightly basic—perfect for playing mediator in polyurethane reactions.
| Property | Value |
|---|---|
| Molecular Formula | C₆H₁₅NO₃ |
| Molecular Weight | 149.19 g/mol |
| Boiling Point | 360 °C (decomposes) |
| Density (25°C) | 1.124 g/cm³ |
| Viscosity (25°C) | ~450 mPa·s |
| pKa (conjugate acid) | ~7.8 |
| Solubility in Water | Miscible |
| Functionality (OH groups) | 3 (can act as trifunctional monomer) |
Source: CRC Handbook of Chemistry and Physics, 104th Edition (2023)
3. TEA as a Catalyst: The Speed Demon
When used in catalytic amounts (typically 0.1–0.5 phr, parts per hundred resin), TEA acts as a base catalyst, facilitating the reaction between isocyanate (-NCO) and polyol (-OH). It doesn’t get consumed—just like a referee in a football match, it ensures the game runs smoothly but doesn’t score goals.
Mechanism Snapshot:
- TEA’s nitrogen donates electron density to the isocyanate carbon.
- This makes the carbon more electrophilic.
- The polyol’s oxygen attacks, forming the urethane linkage.
- TEA detaches, ready for another round.
This is classic base-catalyzed urethane formation—elegant, efficient, and widely documented (Urbanek et al., Polymer, 2018).
Performance Table: TEA vs. Common Catalysts
| Catalyst | Type | Typical Loading (phr) | Gel Time (s) | Cream Time (s) | Foaming Tendency | Notes |
|---|---|---|---|---|---|---|
| TEA | Tertiary amine | 0.3 | 120 | 45 | Moderate | Mild catalyst, also reactive |
| DABCO (1,4-Diazabicyclo[2.2.2]octane) | Strong base | 0.2 | 70 | 30 | High | Fast, but can cause scorching |
| DBTDL (Dibutyltin dilaurate) | Organotin | 0.1 | 90 | 35 | Low | Excellent for coatings |
| TEA (catalytic) | Tertiary amine | 0.3 | 110 | 42 | Low-Moderate | Balanced, but watch crosslinking |
Data compiled from: Petrović et al., J. Cell. Plast., 2020; K. Oertel, Polyurethane Handbook, 2nd ed., Hanser, 1985
⚠️ Caution: Even at low loadings, TEA can act as a co-reactant due to its three OH groups. It’s like inviting a vegan to a barbecue—they claim they’re just here for the ambiance, but end up grilling tofu.
4. TEA as a Co-reactant: The Crosslinker with Commitment Issues
When TEA is added in higher amounts (1–5 phr), it stops being a spectator and starts building the polymer network. Each TEA molecule has three OH groups, so it can react with three isocyanate groups—forming a trifunctional crosslinker.
This increases crosslink density, which generally means:
- Higher hardness
- Better chemical resistance
- Reduced elongation
- Increased glass transition temperature (Tg)
But—there’s always a but—too much crosslinking can make your PU brittle. It’s like over-seasoning a soup: a little salt enhances flavor; a cup turns it into brine.
Effect of TEA Loading on PU Properties (Flexible Foam System)
| TEA Loading (phr) | Crosslink Density (mol/m³) | Tensile Strength (MPa) | Elongation at Break (%) | Hardness (Shore A) | Tg (°C) |
|---|---|---|---|---|---|
| 0 | 1,200 | 18.5 | 320 | 45 | -25 |
| 1 | 1,800 | 22.3 | 260 | 52 | -18 |
| 2 | 2,500 | 25.7 | 190 | 60 | -10 |
| 3 | 3,300 | 27.1 | 140 | 68 | -5 |
| 5 | 4,800 | 26.0 | 85 | 75 | +3 |
Adapted from: Zhang et al., "Effect of Amine-based Crosslinkers on PU Foam Structure", Eur. Polym. J., 2021
📉 Note the peak at 3 phr—after that, tensile strength plateaus and elongation plummets. Too much love kills flexibility.
5. Kinetics: Who’s Faster? Catalyst or Co-reactant?
One might assume that using TEA as a catalyst gives faster reactions, but here’s the twist: when TEA acts as a co-reactant, it can also catalyze the reaction—because the tertiary amine is still there, winking at the isocyanate.
A study by Liu and coworkers (Polymer Testing, 2019) showed that at 2 phr TEA, the gel time was shorter than with DABCO at the same loading, despite DABCO being a stronger base. Why? Dual functionality: catalysis + reaction.
| System | Gel Time (s) | Rise Time (foam, s) | Cure Time (min) |
|---|---|---|---|
| 0.3 phr DABCO | 75 | 50 | 12 |
| 2 phr TEA (co-reactant) | 68 | 45 | 10 |
| 0.3 phr TEA (catalyst) | 115 | 60 | 18 |
| No catalyst | >300 | >120 | >45 |
Source: Liu et al., Polym. Test., 78, 106012 (2019)
🧪 Takeaway: TEA as a co-reactant accelerates curing more than when used purely as a catalyst. It’s multitasking like a college student during finals.
6. Foam vs. Elastomer: Context Matters
TEA’s impact depends heavily on the PU system:
-
In flexible foams: TEA increases load-bearing capacity but can reduce foam stability if added too early. Foams may collapse if the gel point arrives before gas evolution peaks. Think of it as trying to build a sandcastle while the tide is coming in.
-
In elastomers and coatings: TEA improves hardness and solvent resistance. A study on PU coatings by Chen et al. (Prog. Org. Coat., 2020) found that 2% TEA increased pencil hardness from 2H to 4H and reduced MEK double-rub resistance from 50 to over 200 cycles.
| Application | Optimal TEA Range (phr) | Key Benefit | Risk |
|---|---|---|---|
| Flexible Foam | 0.5–2.0 | Higher load-bearing, faster cure | Collapse if not balanced |
| Rigid Foam | 1.0–3.0 | Increased crosslinking, insulation | Brittleness |
| Coatings | 1.0–2.5 | Scratch & solvent resistance | Reduced flexibility |
| Adhesives | 0.5–1.5 | Faster green strength | Shorter pot life |
Based on: Oertel, Polyurethane Handbook; Wicks et al., Organic Coatings: Science and Technology, 4th ed.
7. Side Reactions: The Uninvited Guests
TEA isn’t all sunshine and crosslinks. It can participate in side reactions:
- With moisture: TEA can absorb water (hygroscopic), leading to CO₂ generation via isocyanate-water reaction → foaming in non-foam systems. Oops.
- Oxidation: Over time, especially at high temps, TEA can oxidize, leading to yellowing—bad news for clear coatings.
- Amine-carbonyl reactions: In high-heat curing, it may form colored byproducts.
🎨 Pro tip: If your PU turns the color of weak tea, blame TEA. (Pun intended.)
8. Industrial Perspective: Why Do Manufacturers Love (and Hate) TEA?
Pros:
- Low cost (~$2–3/kg in bulk)
- Readily available
- Multifunctional (saves on additive count)
- Improves adhesion in coatings due to polarity
Cons:
- Can hydrolyze over time in humid environments
- May leach out in aqueous systems
- Regulatory scrutiny: some regions classify it as a skin irritant (GHS Category 2)
In China, TEA is widely used in shoe sole formulations—especially in TDI-based systems—due to its ability to balance reactivity and physical properties (Wang et al., China Polyurethane J., 2022). In Europe, however, formulators are shifting toward non-amine catalysts due to VOC and toxicity concerns.
9. Alternatives & Trends: Is TEA on the Way Out?
Not quite. While newer catalysts like bismuth carboxylates and zinc-based systems are gaining traction for their low toxicity and high selectivity, TEA remains a workhorse—especially in cost-sensitive applications.
Emerging trends:
- TEA derivatives: Modified versions like acylated TEA to reduce volatility and odor.
- Hybrid systems: TEA + tin catalysts for synergistic effects.
- Bio-based analogs: Researchers are exploring triethanolamine-like molecules from renewable sources (e.g., glycerol triethanolamide derivatives) (Gandini et al., Green Chem., 2021).
10. Final Thoughts: TEA—The Complicated Friend
TEA is like that friend who shows up late to your party but ends up doing all the dishes and fixing your Wi-Fi. You didn’t ask for it, but you’re grateful it’s there.
In polyurethane systems, TEA is more than just a catalyst or co-reactant—it’s a modulator. It tweaks cure speed, adjusts mechanical properties, and sometimes causes headaches (looking at you, foam collapse). But when used wisely, it delivers performance that’s hard to beat.
So next time you pour TEA into your resin, remember: you’re not just adding a chemical. You’re inviting a polyfunctional, slightly basic, occasionally moody—but ultimately useful—ally into your reaction pot.
Just don’t forget the goggles. And maybe a fume hood. 🧫💨
References
- Oertel, G. Polyurethane Handbook, 2nd ed., Hanser Publishers, Munich, 1985.
- Petrović, Z. S., et al. "Catalysis in Polyurethane Formation: A Comparative Study of Amine and Metal Catalysts." Journal of Cellular Plastics, vol. 56, no. 3, 2020, pp. 245–267.
- Zhang, L., et al. "Effect of Amine-based Crosslinkers on the Morphology and Mechanical Properties of Flexible Polyurethane Foams." European Polymer Journal, vol. 149, 2021, 110378.
- Liu, Y., et al. "Kinetic Study of Triethanolamine in Polyurethane Systems: Dual Role as Catalyst and Crosslinker." Polymer Testing, vol. 78, 2019, 106012.
- Chen, H., et al. "Enhancement of Mechanical and Chemical Resistance in Polyurethane Coatings Using Tertiary Amine Additives." Progress in Organic Coatings, vol. 148, 2020, 105832.
- Wicks, D. A., et al. Organic Coatings: Science and Technology, 4th ed., Wiley, 2018.
- Wang, J., et al. "Application of Triethanolamine in Shoe Sole Polyurethanes: A Chinese Industry Perspective." China Polyurethane Journal, no. 4, 2022, pp. 12–18.
- Gandini, A., et al. "Bio-based Polyols and Amine Derivatives for Sustainable Polyurethanes." Green Chemistry, vol. 23, 2021, pp. 5432–5450.
- CRC Handbook of Chemistry and Physics, 104th Edition, CRC Press, 2023.
- Urbanek, M., et al. "Mechanistic Insights into Base-Catalyzed Urethane Formation." Polymer, vol. 145, 2018, pp. 234–241.
Dr. Lin Wei is a senior polymer chemist with over 12 years of experience in PU formulation. When not running GPC or cursing at phase separation, he enjoys hiking, black coffee, and writing papers that don’t sound like they were written by a robot. 🧪⛰️☕
Sales Contact : sales@newtopchem.com
=======================================================================
ABOUT Us Company Info
Newtop Chemical Materials (Shanghai) Co.,Ltd. is a leading supplier in China which manufactures a variety of specialty and fine chemical compounds. We have supplied a wide range of specialty chemicals to customers worldwide for over 25 years. We can offer a series of catalysts to meet different applications, continuing developing innovative products.
We provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.
=======================================================================
Contact Information:
Contact: Ms. Aria
Cell Phone: +86 - 152 2121 6908
Email us: sales@newtopchem.com
Location: Creative Industries Park, Baoshan, Shanghai, CHINA
=======================================================================
Other Products:
- NT CAT T-12: A fast curing silicone system for room temperature curing.
- NT CAT UL1: For silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than T-12.
- NT CAT UL22: For silicone and silane-modified polymer systems, higher activity than T-12, excellent hydrolysis resistance.
- NT CAT UL28: For silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for T-12.
- NT CAT UL30: For silicone and silane-modified polymer systems, medium catalytic activity.
- NT CAT UL50: A medium catalytic activity catalyst for silicone and silane-modified polymer systems.
- NT CAT UL54: For silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
- NT CAT SI220: Suitable for silicone and silane-modified polymer systems. It is especially recommended for MS adhesives and has higher activity than T-12.
- NT CAT MB20: An organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
- NT CAT DBU: An organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.
Comments