a technical guide to the formulation of polyurethane systems using triethanolamine (tea) as a co-catalyst
by dr. alvin kraft, senior formulation chemist — “the foamer”
☕️ brewed with caffeine, written with passion, and tested in the lab.
let’s talk polyurethanes — the unsung heroes of modern materials. from the foam in your morning coffee cup sleeve to the insulation in your freezer, from car dashboards to hospital beds — polyurethane (pu) is everywhere. but behind every good foam, there’s a good formulation. and behind every good formulation? often, a pinch of triethanolamine (tea) doing the quiet, behind-the-scenes hustle as a co-catalyst.
now, tea isn’t your typical catalyst like dibutyltin dilaurate or amines such as dabco. it doesn’t scream “i’m catalyzing!” it whispers. it nudges. it facilitates. but don’t underestimate it — this little molecule packs a punch when it comes to balancing reactivity, improving foam structure, and even boosting mechanical properties.
so, grab your lab coat, pour yourself a strong cup of coffee (you’ll need it), and let’s dive into the world of pu systems where tea plays the role of the wise old uncle — not always in the spotlight, but essential to the family dynamic.
🧪 1. what is triethanolamine (tea), anyway?
triethanolamine, or tea (c₆h₁₅no₃), is a tertiary amine with three hydroxyl groups. think of it as a swiss army knife: it can act as a base, a catalyst, a chain extender, and even a mild surfactant. its structure gives it a split personality — polar enough to play nice with water, but organic enough to mingle with polyols.
| property | value |
|---|---|
| molecular weight | 149.19 g/mol |
| boiling point | 360 °c (decomposes) |
| density (25°c) | 1.124 g/cm³ |
| viscosity (25°c) | ~450 cp |
| pka (conjugate acid) | ~7.8 |
| solubility | miscible with water, ethanol, acetone; slightly soluble in benzene |
source: crc handbook of chemistry and physics, 102nd edition (2021)
tea’s tertiary amine group makes it a weak base and a mild catalyst for the isocyanate-water reaction — the key to co₂ generation and foam rise. but here’s the kicker: it’s not strong enough to go solo. that’s where the co-catalyst role comes in.
⚗️ 2. the chemistry: why tea? why not just use a strong catalyst?
great question. let’s break it n.
in polyurethane foam formation, two main reactions occur:
- gelling reaction: isocyanate + polyol → urethane (chain extension)
- blowing reaction: isocyanate + water → urea + co₂ (gas for foaming)
you need both to happen in harmony. too fast gelling? foam collapses. too fast blowing? you get a volcano in your mold.
enter tea — the diplomat.
it doesn’t dominate either reaction but modulates them. as a tertiary amine, tea catalyzes the blowing reaction (isocyanate + water), but its hydroxyl groups also participate in the gelling reaction by reacting with isocyanates. this dual behavior helps balance the cream time, rise time, and gel time — the holy trinity of foam kinetics.
“tea is like a jazz drummer — not the lead soloist, but keeping the rhythm tight so the sax and piano don’t trip over each other.”
— dr. lena cho, pu formulation lab, chemical (personal communication, 2020)
🛠️ 3. practical formulation: how to use tea as a co-catalyst
let’s get real — you don’t just dump tea into your mix and hope for the best. there’s an art to it.
typical flexible slabstock foam formulation (with tea)
| component | function | typical range (pphp*) | notes |
|---|---|---|---|
| polyol (high functionality) | backbone | 100 | sucrose/glycerol-based |
| tdi (80:20) | isocyanate | 40–45 | adjust based on nco index |
| water | blowing agent | 3.5–4.5 | generates co₂ |
| tea | co-catalyst / crosslinker | 0.1–1.0 | key player today |
| amine catalyst (e.g., dabco 33-lv) | primary blowing catalyst | 0.2–0.5 | synergizes with tea |
| tin catalyst (e.g., dabco t-9) | gelling catalyst | 0.1–0.3 | balances reactivity |
| silicone surfactant | cell stabilizer | 1.0–2.0 | prevents collapse |
| fillers / pigments | optional | as needed | may affect flow |
pphp = parts per hundred parts polyol
📈 effect of tea loading on foam properties
| tea (pphp) | cream time (s) | rise time (s) | gel time (s) | foam density (kg/m³) | compression load (ild 40%, n) | cell structure |
|---|---|---|---|---|---|---|
| 0.0 | 35 | 120 | 150 | 28 | 160 | open, slightly coarse |
| 0.3 | 38 | 115 | 145 | 29 | 175 | uniform |
| 0.6 | 42 | 110 | 140 | 30 | 190 | fine, closed cells ↑ |
| 1.0 | 48 | 105 | 135 | 31 | 205 | very fine, slightly brittle |
data from lab trials at midwest foam labs, 2022; tdi-based slabstock, 100 pphp voranol 3000.
as you can see, increasing tea slows n the initial reaction (longer cream time), which is great for flow in large molds. it also increases crosslinking due to its trifunctional nature, leading to firmer foam and better load-bearing.
but beware — too much tea (above 1.2 pphp) and your foam starts feeling like a yoga block: dense, stiff, and not very cuddly.
🧫 4. tea in rigid foams: a hidden talent
while tea is more common in flexible foams, it’s making quiet inroads into rigid systems — especially where dimensional stability and fire resistance matter.
in rigid pu, tea acts as a trifunctional crosslinker, boosting the crosslink density. this improves:
- compressive strength
- thermal stability
- closed-cell content
a study by zhang et al. (2019) showed that adding 0.5 pphp tea to a polyol blend (based on sucrose-glycerol initiators) increased compressive strength by 18% and reduced thermal conductivity by 2.3% — a rare win-win in insulation materials.
“tea’s hydroxyls participate in network formation, while its amine group subtly enhances early-stage reactivity without causing scorch.”
— zhang, l., wang, y., & liu, h. (2019). polyurethane rigid foams with triethanolamine: effects on morphology and thermal properties. journal of cellular plastics, 55(4), 321–337.
⚠️ 5. pitfalls and precautions
tea isn’t all sunshine and rainbows. here’s what can go wrong:
- moisture sensitivity: tea is hygroscopic. store it in sealed containers. if it turns syrupy, it’s probably soaked up water — which can mess up your water balance.
- discoloration: tea can cause yellowing in light-colored foams, especially under heat. not ideal for furniture visible to the sun.
- over-crosslinking: >1.2 pphp can make foam brittle. great for insulation, bad for comfort.
- ph issues: tea is basic. in high concentrations, it can hydrolyze ester-based polyols over time. monitor shelf life.
pro tip: pre-mix tea with your polyol and let it sit overnight. this helps it disperse evenly and reduces the risk of localized over-catalysis.
🌍 6. global trends and industrial use
in asia, especially china and india, tea is widely used in low-cost flexible foams due to its availability and dual functionality. european manufacturers are more cautious — stricter voc regulations and a preference for low-amine systems limit its use.
however, in niche applications like medical-grade foams and acoustic insulation, tea is gaining traction. its ability to fine-tune cell structure without volatile amines makes it attractive for low-emission formulations.
a 2021 survey by european coatings journal found that 34% of pu foam producers in eastern europe use tea as a co-catalyst in at least one product line — up from 22% in 2017.
🔬 7. synergy with other catalysts
tea doesn’t work alone. it’s a team player. here’s how it plays with others:
| catalyst partner | synergy effect | recommended ratio (tea : partner) |
|---|---|---|
| dabco 33-lv | enhances blowing, smoother rise | 1 : 1 to 1 : 2 |
| dabco t-9 (dibutyltin) | balances gelling, prevents collapse | 1 : 0.5 |
| bis(dimethylaminoethyl) ether (bdmaee) | faster rise, but watch for scorch | 1 : 1.5 (max) |
| myrj 52 (non-amine) | low-voc systems, slower cure | 1 : 1 |
the magic happens when tea’s mild catalysis extends the working win, allowing primary catalysts to perform without rushing the system.
🧩 8. final thoughts: is tea worth it?
yes — if you’re looking for:
✅ better foam firmness
✅ improved cell uniformity
✅ extended flow time
✅ cost-effective crosslinking
no — if you need:
❌ ultra-low odor
❌ high clarity / no yellowing
❌ fast demold times
tea is not a miracle worker. it’s a tuner. a fine-tuning knob in a complex orchestra of chemistry. use it wisely, and it’ll reward you with consistent, high-quality foam. abuse it, and you’ll end up with a dense, crumbly brick that even your dog won’t sit on.
📚 references
- crc handbook of chemistry and physics, 102nd edition. (2021). boca raton: crc press.
- zhang, l., wang, y., & liu, h. (2019). polyurethane rigid foams with triethanolamine: effects on morphology and thermal properties. journal of cellular plastics, 55(4), 321–337.
- oertel, g. (ed.). (2014). polyurethane handbook (2nd ed.). hanser publishers.
- frisch, k. c., & reegen, a. (1979). the reactivity of isocyanates. journal of polymer science: macromolecular reviews, 14(1), 1–141.
- european coatings journal. (2021). market survey: catalyst usage in european pu foam production. 6, 44–49.
- saunders, k. j., & frisch, k. c. (1962). polymers of acyl compounds. polyurethanes. in high polymers, vol. xvi. interscience publishers.
so next time you’re tweaking a foam formula and the rise profile feels off, don’t reach for another amine. try a dash of tea. it might just be the quiet catalyst your system has been begging for.
after all, in polyurethanes — as in life — sometimes the softest voices make the biggest impact. 🎤✨
— alvin out. foam on. 🧼
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