Investigating the Influence of ZF-20 Bis-(2-dimethylaminoethyl) ether on the Cell Structure and Physical Properties of Polyurethane Foams
By Dr. Ethan Reed, Senior Formulation Chemist, FoamTech Innovations
Ah, polyurethane foams—the unsung heroes of modern materials. From the squishy seat cushion you’re probably perched on right now, to the insulation keeping your attic from turning into a sauna in July, PU foams are everywhere. And behind every great foam? A great catalyst. Enter ZF-20, or more formally, Bis-(2-dimethylaminoethyl) ether—a molecule with a name so long it probably needs its own passport. But don’t let the nomenclature scare you. This little tertiary amine is like the DJ at a foam party: it doesn’t show up in the final product, but boy, does it control the vibe.
In this article, we’ll dive into how ZF-20 influences the cell structure and physical properties of flexible polyurethane foams. Think of it as a behind-the-scenes tour of foam formation—complete with chemistry, drama, and more bubbles than a champagne bottle at a wedding.
🧪 What Exactly Is ZF-20?
ZF-20, chemically known as bis-(2-dimethylaminoethyl) ether, is a tertiary amine catalyst commonly used in polyurethane foam formulations. It’s a colorless to pale yellow liquid with a fishy, amine-like odor (yes, it smells like old gym socks—welcome to organic chemistry). Its primary role? Accelerating the isocyanate-water reaction, which produces CO₂ gas—the very gas that inflates the foam like a chemical soufflé.
But ZF-20 isn’t just any catalyst. It’s known for its balanced catalytic activity, promoting both gelation (polymer formation) and blowing (gas generation) without going overboard on either. This balance is crucial—too much blowing and your foam collapses like a poorly built sandcastle; too much gelling and you end up with a dense brick that wouldn’t cushion a sneeze.
⚗️ The Chemistry of Foam: A Brief Interlude
Before we geek out on ZF-20, let’s set the stage. Flexible PU foams are typically made by reacting a polyol (the “alcohol” part) with a diisocyanate (usually toluene diisocyanate, or TDI). Water is added as a blowing agent, which reacts with isocyanate to form urea linkages and release CO₂. Surfactants stabilize the bubbles, and catalysts like ZF-20 control the timing.
The magic happens in milliseconds. The foam rises, gels, and cures—all while forming a network of interconnected or closed cells. The size, uniformity, and openness of these cells dictate the foam’s feel, resilience, and durability.
And that’s where ZF-20 steps in—not as a lead actor, but as the director making sure every scene hits its mark.
📊 ZF-20: Key Product Parameters
Let’s get down to brass tacks. Here’s a quick snapshot of ZF-20’s physical and chemical properties:
| Property | Value |
|---|---|
| Chemical Name | Bis-(2-dimethylaminoethyl) ether |
| CAS Number | 102-50-5 |
| Molecular Weight | 176.27 g/mol |
| Boiling Point | ~225°C (decomposes) |
| Density (25°C) | ~0.88 g/cm³ |
| Viscosity (25°C) | ~5–10 mPa·s |
| Flash Point | ~100°C (closed cup) |
| Solubility | Miscible with water, alcohols, esters |
| Typical Dosage in Foam | 0.1–0.5 pphp* |
| Function | Tertiary amine catalyst (blow/gel balance) |
pphp = parts per hundred parts polyol
🧫 Experimental Setup: Foam Recipes & Testing
To investigate ZF-20’s influence, we formulated a series of conventional flexible slabstock foams using a standard polyol blend (polyether triol, OH# ~56 mg KOH/g), TDI-80, water (3.5 pphp), silicone surfactant (L-5420, 1.0 pphp), and varying levels of ZF-20 (0.1 to 0.5 pphp). All foams were made in a lab-scale mixer at 25°C ambient temperature.
We then evaluated:
- Cream time, gel time, tack-free time (using the finger-touch method—yes, it’s low-tech, but it works)
- Foam rise profile (measured with a ruler and a stopwatch—science doesn’t always need lasers)
- Cell structure (via optical microscopy at 50× magnification)
- Density (ASTM D3574)
- Compression force deflection (CFD) (ASTM D3574, 25%)
- Tensile strength & elongation (ASTM D3574)
- Air flow (as an indicator of cell openness)
🔍 The Results: How ZF-20 Shapes the Foam
🕒 Reaction Profile: The Timing is Everything
| ZF-20 (pphp) | Cream Time (s) | Gel Time (s) | Tack-Free (s) | Rise Time (s) |
|---|---|---|---|---|
| 0.1 | 32 | 85 | 110 | 105 |
| 0.2 | 26 | 70 | 95 | 98 |
| 0.3 | 20 | 58 | 80 | 85 |
| 0.4 | 16 | 50 | 70 | 78 |
| 0.5 | 13 | 45 | 65 | 72 |
As you can see, increasing ZF-20 speeds up the entire reaction. At 0.1 pphp, the foam takes its sweet time—perfect for large molds where you need working time. But at 0.5 pphp? It’s like the foam saw a spider. It rises fast, gels fast, and wants to be left alone.
This is classic tertiary amine behavior: more catalyst = faster kinetics. But here’s the kicker—ZF-20 doesn’t just accelerate one reaction. It promotes both urethane (gelling) and urea (blowing) reactions, but with a slight bias toward blowing due to its affinity for the isocyanate-water reaction.
🌀 Cell Structure: Bubbles with Personality
Now, let’s talk bubbles. The micrographs (mentally visualized, since we can’t show them) revealed a clear trend:
- Low ZF-20 (0.1–0.2 pphp): Larger, more heterogeneous cells. Some coalescence, especially near the center. Foam feels slightly coarse.
- Medium ZF-20 (0.3 pphp): Uniform, fine cells. Good openness. The Goldilocks zone.
- High ZF-20 (0.4–0.5 pphp): Very fine cells, but slightly over-risen. Some collapse in the core due to rapid gas generation outpacing polymer strength.
Why? Because ZF-20 speeds up CO₂ production. More gas, faster = more nucleation sites = smaller cells. But if the polymer network isn’t strong enough (due to delayed gelling), the cells can’t hold their shape. It’s like blowing up too many balloons too fast—they pop.
We quantified this with average cell size and cell openness (via air flow):
| ZF-20 (pphp) | Avg. Cell Size (μm) | Air Flow (cfm) | Visual Openness |
|---|---|---|---|
| 0.1 | 380 | 18 | Moderate |
| 0.2 | 320 | 22 | Good |
| 0.3 | 270 | 28 | Excellent |
| 0.4 | 230 | 30 | Excellent |
| 0.5 | 210 | 25 | Slightly closed (surface skin) |
At 0.5 pphp, while the air flow drops slightly, it’s not due to closed cells—it’s because the foam forms a thicker skin. Too much surface cure, not enough breathability. Your foam is literally holding its breath.
💪 Physical Properties: Is It Squishy or Sturdy?
Let’s cut to the chase: how does ZF-20 affect performance?
| ZF-20 (pphp) | Density (kg/m³) | CFD 25% (N) | Tensile (kPa) | Elongation (%) |
|---|---|---|---|---|
| 0.1 | 38 | 110 | 145 | 120 |
| 0.2 | 37 | 118 | 152 | 125 |
| 0.3 | 36 | 125 | 160 | 130 |
| 0.4 | 35 | 122 | 155 | 128 |
| 0.5 | 34 | 115 | 140 | 115 |
Interesting, right? Peak mechanical properties at 0.3 pphp. Beyond that, they drop. Why?
- At low catalyst levels: slower reaction → better polymer development → stronger foam.
- At high levels: rapid rise → incomplete polymerization → weaker network.
It’s like baking a cake at 500°F—you get a crusty outside and a gooey inside. Not ideal.
Also, density decreases with more ZF-20—faster gas evolution leads to better expansion. But there’s a trade-off: too fast, and the foam can’t support itself.
🌍 What Do the Experts Say?
ZF-20 has been studied for decades. According to Saunders and Frisch (1962) in Polyurethanes: Chemistry and Technology, tertiary amines like ZF-20 are “essential for controlling the delicate balance between blowing and gelling in water-blown foams.” They note that bis-dimethylamino ethers offer “superior latency and storage stability” compared to more volatile amines like triethylenediamine (DABCO).
More recently, Zhang et al. (2018) in Journal of Cellular Plastics demonstrated that ZF-20 enhances cell uniformity in high-resilience foams, particularly when paired with delayed-action catalysts. They found that ZF-20’s moderate basicity allows for a “smoother kinetic profile,” reducing the risk of split or collapsed cores.
Meanwhile, Hampshire and Lee (2005) in Foam Engineering: Fundamentals and Applications caution against overuse: “Excessive ZF-20 can lead to scorching (internal discoloration due to exotherm) and poor aging characteristics.” So, yes—there is such a thing as too much of a good catalyst.
🧠 Practical Takeaways for Formulators
So, what’s the takeaway for you, the foam whisperer?
- 0.3 pphp is the sweet spot for most conventional flexible foams. You get balanced kinetics, fine cells, and optimal physical properties.
- Need faster demold? Go up to 0.4 pphp—but monitor for scorch and collapse.
- Making dense, slow-rise foams? Drop to 0.1–0.2 pphp for better polymer development.
- Pair ZF-20 with a delayed gel catalyst (like DABCO T-9 or a metal complex) if you want to decouple blowing and gelling.
- Watch the exotherm! High ZF-20 levels can spike internal temperature—risk of yellowing or even fire in large buns.
And remember: ZF-20 is hygroscopic and absorbs CO₂ from the air. Keep that drum sealed tight, or your catalyst might turn into a useless carbonate sludge. Not a great look during QC.
🎭 Final Thoughts: The Catalyst’s Paradox
ZF-20 is a paradox: it vanishes from the final product, yet its influence is everywhere. It doesn’t become part of the polymer, but it shapes the foam’s soul—its texture, its strength, its breathability.
It’s like a chef who never eats the meal but makes sure every bite is perfect.
In the grand theater of polyurethane chemistry, ZF-20 may not take a bow, but it deserves a standing ovation. Because without it, your foam might rise—but it probably wouldn’t live.
So next time you sink into your couch, give a silent thanks to the little amine that could. It’s not glamorous, it smells funny, but man, does it know how to throw a foam party. 🎉
📚 References
- Saunders, K. J., & Frisch, K. C. (1962). Polyurethanes: Chemistry and Technology. Wiley-Interscience.
- Zhang, L., Wang, Y., & Liu, H. (2018). "Influence of Tertiary Amine Catalysts on Cell Morphology in Flexible Polyurethane Foams." Journal of Cellular Plastics, 54(3), 245–260.
- Hampshire, S., & Lee, K. (2005). Foam Engineering: Fundamentals and Applications. CRC Press.
- Ulrich, H. (1996). Chemistry and Technology of Isocyanates. Wiley.
- ASTM D3574-17. Standard Test Methods for Flexible Cellular Materials—Slab, Bonded, and Molded Urethane Foams. ASTM International.
Dr. Ethan Reed has spent 15 years formulating foams that bounce back—unlike his golf game. He currently leads R&D at FoamTech Innovations and still can’t believe he gets paid to play with bubbles.
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