Three polyamines dominate low-molecular-weight amine work – TREN (CAS 4097-89-6), TETA (112-24-3) and DETA (111-40-0) – and they are routinely quoted against each other as if they were grades of the same thing. They are not. This article sets out what actually differs, and how to choose without paying speciality prices for a commodity job or commodity prices for a speciality one.
The Numbers That Look Alike
| Property | TREN | TETA | DETA |
|---|---|---|---|
| CAS | 4097-89-6 | 112-24-3 | 111-40-0 |
| Formula / MW | C6H18N4 / 146.23 | C6H18N4 / 146.24 | C4H13N3 / 103.17 |
| Amine types | 3 primary + 1 tertiary | 3 primary + 1 secondary | 2 primary + 1 secondary |
| Active hydrogens | 6 | 6 | 5 |
| Amine equivalent weight | 24.4 g/eq | 24.4 g/eq | 20.6 g/eq |
| Structure | Branched tetraamine | Linear tetraamine | Linear triamine |
| Typical supply | Distilled 98%+ | Bulk, several grades | Bulk, several grades |
TREN and TETA are isomers: identical formula, identical molecular weight, identical equivalent weight. DETA is a smaller molecule with a lower equivalent weight, which is why it is dosed higher and cures faster. Everything that matters after this table follows from structure, not from the numbers.
Epoxy Curing: Where the Isomer Shows Up
Stoichiometry is the same for TREN and TETA – phr = 24.4 x 100 / EEW – so a formulator switching between them at the same loading keeps the same crosslink density target. What changes is the kinetics:
| Behaviour | TREN | TETA | DETA |
|---|---|---|---|
| Gel time at stoichiometry | Shortest of the three (self-accelerated) | Moderate | Short (high amine density) |
| External accelerator needed | Normally none | Often yes for low temperature or thin film | Less often |
| Pot life control | Hard – catalyst is built in; use temperature | Easier | Easier than TREN, harder than TETA |
| Exotherm / yellowing risk | Higher | Lower | High |
| Typical loading at EEW 185 | 13.2 phr | 13.2 phr | 11.1 phr |
DETA’s 11.1 phr is 20.6 x 100 / 185. The lower figure is not a saving: there is more reactive amine per gram, so the reaction is faster and hotter per unit weight, and water resistance and flexibility are typically worse than the longer-chain amines. On a cost-per-kilogram basis DETA often looks cheapest and on a cost-per-formulated-kilogram basis is often not, because it needs flexibiliser or diluent to get acceptable film properties.
The TREN trade-off is the reverse: you pay a speciality price to get a cure that needs no accelerator and a hardener with a branch point. That is worth it in thin-film, low-temperature or fast-turnaround work, and it is not worth it in a thick cast section where the built-in catalysis turns into an exotherm problem.
Chelation and Coordination Chemistry: Not Close
This is where the three stop being comparable at all. TREN is a tetradentate N4 ligand: three primary arms plus the central tertiary nitrogen coordinate the same metal ion, giving a pre-organised pocket with 1:1 stoichiometry for Cu(II), Zn(II) and Ni(II).
TETA can coordinate more than two sites, but it is a flexible linear chain that must fold around the metal, so the entropic penalty is higher and the geometry less defined. DETA, with only three nitrogens, cannot fill four sites with the same pre-organisation. If the application is a defined metal complex – a catalyst precursor, a chelating polymer, a micronutrient complex – the choice is TREN and the question is only price and availability. If the application is simply "bind some metal ions in a water system", a chelating agent selected for the metal in question (EDTA-type, gluconate, or an EDDHA-type chelate for iron) is usually a better fit than any of these three.
Gas Treating and CO2
All three react with CO2 through their primary amines. What differs is amine density per unit mass and the physical behaviour of the loaded solution. TREN packs four nitrogens into 146 g/mol and is the most studied of the three in aqueous amine CO2 capture work; TETA is its linear twin with different viscosity behaviour on loading; DETA loads less per molecule but is cheaper per mole of amine. The decision here is made on loaded viscosity and regeneration energy, not on capacity on paper – and it should be made with bench data, not with a data sheet.
Hazard and Handling Differences
| Item | TREN | TETA | DETA |
|---|---|---|---|
| Corrosivity | Corrosive | Corrosive | Corrosive, and a recognised skin sensitiser |
| Volatility / odour | Low volatility, amine odour | Low volatility | More volatile – worse in open handling |
| Nitrosamine concern | Tertiary amine – relevant | Secondary amine – relevant | Secondary amine – relevant |
| Metal compatibility | Avoid Cu/Al | Avoid Cu/Al | Avoid Cu/Al |
Do not treat "all three are corrosive amines" as a reason to skip the SDS. DETA’s higher volatility changes the ventilation requirement, and every one of these three is a nitrosamine precursor – secondary and tertiary amines alike – so none of them belongs in a waste stream that also carries nitrite.
Selection Table
| If your requirement is… | Choose | Because |
|---|---|---|
| Fast cure without adding an accelerator, thin film or low temperature | TREN | Tertiary nitrogen self-catalyses |
| Known bulk cure schedule, tonnage pricing | TETA | Same stoichiometry, commodity supply, predictable kinetics |
| Lowest viscosity hardener, high reactivity | DETA | Smaller molecule, lower equivalent weight |
| Defined 1:1 metal complex, tetradentate ligand | TREN | Pre-organised N4 pocket |
| Iron chelation in agriculture | EDDHA-type chelate | Purpose-built chemistry for Fe at high pH |
| CO2 absorption screening | Compare all three on loaded viscosity | Capacity on paper does not predict plant performance |
The Cost Comparison Buyers Get Wrong
Compare on cost per active equivalent, not cost per tonne. The formula is simple:
cost index = price per tonne / amine equivalent weight
Because TREN and TETA share an equivalent weight of 24.4 g/eq, their cost indices differ only by the ratio of their prices – and that ratio can be large, because one is a distilled speciality cut and the other a bulk ethyleneamine. DETA at 20.6 g/eq delivers more equivalents per tonne, which partially offsets its lower price; do the division before concluding DETA is cheapest. And for epoxy work, add the cost of the accelerator that TETA may need but TREN does not – that line item routinely closes the gap.
Frequently Asked Questions
Can I substitute TREN for TETA weight-for-weight?
On stoichiometry yes, because both are 24.4 g/eq. In practice no: TREN cures faster and exotherms harder because of its tertiary nitrogen. Expect a shorter pot life and a different colour; re-check the cure schedule before releasing a formulation change.
Which of the three is the best chelating agent?
TREN, but only if you need a defined metal complex. It is tetradentate and pre-organised. If the job is simply to sequester metal ions, a chelating agent chosen for the specific metal will usually beat all three on cost and performance.
Is TREN the linear or branched isomer?
Branched: three 2-aminoethyl arms on one tertiary nitrogen. TETA is the linear isomer with the same formula, which is exactly why the isomer basis has to be stated on the specification.
References and Disclaimer
- CAS registry numbers and molecular weights: PubChem records for TREN (CID 77731), TETA and DETA.
- Amine equivalent weights and phr values are calculated here from molecular weight and active hydrogen count; confirm against the actual resin, accelerator and cure schedule.
Disclaimer: technical and commercial information for industrial buyers, not a specification or SDS. Follow the supplier’s current SDS and local regulations when handling any of these amines.
PolyBlueChem supplies TREN (CAS 4097-89-6) at 98.0% min GC with 0.5% max water, and can quote the comparison products on request. Tell us the application and the equivalent weight you are working to, and we will confirm the grade and the pack size. TREN product page and current specification.