Hexamethylenediamine (HMDA) CAS 124-09-4

What is Hexamethylenediamine (HMDA)?

Hexamethylenediamine is a straight-chain diamine with six carbons between the two nitrogens, H₂N(CH₂)₆NH₂. That bridge length is not accidental — it is the distance that gives a polyamide chain the right balance of flexibility and crystallinity, and it is why nylon 6,6 exists in the form it does.

It is a white crystalline solid melting at about 42 °C, with a strong amine odour. Like the other solid amines it is traded both as molten bulk — for polyamide plants that consume it continuously — and as a 70% or 80% aqueous solution, which is what most other users take.

It is strongly basic, fully water-soluble and hygroscopic, and it absorbs carbon dioxide from air to form a carbamate. Six carbons apart is too far for the two nitrogens to chelate a single metal ion, so unlike EDA it has no chelant market — its value is entirely in chain-building.

Commercially, HMDA is dominated by one product. Reacted with adipic acid it forms nylon salt, which polymerises to nylon 6,6 — the engineering polyamide behind tyre cord, airbag fabric, automotive components, carpet fibre and industrial textiles. Its second market is hexamethylene diisocyanate, the aliphatic isocyanate used in non-yellowing polyurethane coatings. Everything else is a minor outlet by comparison.

Why hexamethylenediamine specifically

• The right bridge for nylon 6,6. Six carbons between nitrogens gives a polyamide chain that crystallises well, melts high enough to be useful and stays tough rather than brittle. Shorter or longer bridges give polymers with inferior property balance.
• Precursor to HDI. Phosgenated it gives hexamethylene diisocyanate, the aliphatic isocyanate behind light-stable automotive and industrial polyurethane topcoats.
• Two unhindered primary amines. Four active hydrogens on a flexible chain, which makes it useful in epoxy curing where toughness matters more than hardness.
• Flexible rather than chelating. The long bridge removes chelate chemistry entirely and makes the molecule a chain extender instead — a different market from the short diamines.

How HMDA is Manufactured

Hexamethylenediamine is made by hydrogenating adiponitrile, and the interesting variation is one step further back, in how the adiponitrile itself is produced.

• Adiponitrile production. Two main routes. Butadiene is hydrocyanated in two stages with hydrogen cyanide over a nickel catalyst; or acrylonitrile is electrochemically dimerised. Both give adiponitrile, and both require substantial dedicated infrastructure — which is why HMDA is made by a small number of very large producers.
• Nitrile hydrogenation. Adiponitrile is hydrogenated over a Raney nickel or cobalt catalyst, usually with ammonia present to suppress formation of secondary amines. Both nitrile groups are reduced to primary amines.
• By-product control. The principal by-products are hexamethyleneimine — a cyclic secondary amine from intramolecular reaction — and bis(hexamethylene)triamine from intermolecular coupling. Ammonia pressure suppresses both, and the residual levels are the key quality figures.
• Finishing. The product is purified by distillation and taken either as molten material under nitrogen or dissolved to make the 70% or 80% aqueous solution.

Typical Commercial Specification

Figures below are representative of polymer-grade material. Technical and 70% solution grades are available — send us the specification you work to and we will quote against it.

Physical & Chemical Properties

Reactivity in practice

Two unhindered primary amines on a flexible six-carbon chain. Chain-building is what it does:

• Polyamide formation. Reaction with adipic acid gives the 1:1 nylon salt, which polycondenses with loss of water to nylon 6,6. With other dibasic acids it gives the wider nylon 6,X family.
• Isocyanate conversion. Phosgenated to hexamethylene diisocyanate, the aliphatic diisocyanate used where a polyurethane coating must not yellow.
• Epoxide ring opening. Four active hydrogens crosslink epoxy resin, with the long flexible bridge giving a tougher, less brittle network than a short diamine.
• Quaternisation and polymerisation. Reaction with difunctional partners gives cationic polymers used as flocculants and water-treatment coagulants.

HMDA vs the Shorter Diamines

Aliphatic diamines are chosen almost entirely on the length of the bridge between the two nitrogens. That distance decides whether the molecule can chelate a metal, how flexible a polymer chain built from it will be, and how readily it closes into a ring instead of reacting the way you intended.

Stated plainly: two carbons is the chelating distance and nothing else comes close; three carbons gives a six-membered chelate ring that binds less strongly but makes a tougher epoxy network; six carbons is too far apart to chelate at all but exactly right for a polyamide chain with the flexibility and melting point that nylon 6,6 needs. The bridge is the design variable, and substituting across it is always a reformulation.

Industries We Supply HMDA To

The same molecule leaves our warehouse for very different factories. What changes between them is the grade — polymer grade is a genuinely different specification — the form, and the documentation each sector expects.

Where HMDA is Used

HMDA is overwhelmingly a polymer raw material. These are the end uses our customers buy it for, roughly in order of volume.

In nylon 6,6 production

This is the dominant global use and the reason HMDA is made at the scale it is. HMDA and adipic acid are combined in precise 1:1 stoichiometry to form nylon salt — a crystalline intermediate that guarantees the exact balance needed for high molecular weight — which is then polycondensed with removal of water. The six-carbon bridge gives a chain that crystallises well, melts around 260 °C and stays tough, which is the combination that makes nylon 6,6 suitable for tyre cord, airbag fabric and under-bonnet automotive parts. Monofunctional and trifunctional impurities are the enemy here, because stoichiometry and linearity are what deliver molecular weight.

In HDI and light-stable coatings

Phosgenating HMDA gives hexamethylene diisocyanate, which — being aliphatic rather than aromatic — produces polyurethane coatings that do not yellow on UV exposure. HDI and its trimers and biurets are behind automotive refinish clearcoats, aerospace topcoats and exterior architectural finishes. This places HMDA alongside IPDA as one of the two foundations of the light-stable polyurethane coating industry.

As an epoxy curing agent

Four active hydrogens on a flexible six-carbon chain give a cured network with long segments between crosslinks — tough and impact-resistant rather than hard and brittle. HMDA is used where that toughness matters, in structural adhesives and flexible coatings, usually as an adduct rather than neat because its melting point makes handling the pure material awkward.

In water treatment polymers

Reacting HMDA with difunctional partners gives cationic polymers used as coagulants in municipal and industrial water treatment. The positive charge neutralises the negative surface charge on suspended solids, allowing them to agglomerate and settle. It is a smaller outlet than polyamide but a steady one.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis. The methods behind the numbers are standard across the industry, and we are happy to share them or to work to your own in-house test protocol.

• Assay and by-product profile — gas chromatography with hexamethyleneimine and bis(hexamethylene)triamine reported explicitly. These two define polymer grade.
• Melting point — a fast, revealing check. A depressed melting point indicates water or by-product contamination before any instrument confirms it.
• Colour and UV transmittance — APHA on melted material plus, for polymer grade, UV transmittance or permanganate time as a measure of trace unsaturated and oxidisable species.
• Water content — Karl Fischer titration on molten grade; solution strength by titration on the aqueous grade.
• Amine value — titration, used to confirm stoichiometry in nylon salt preparation.
• Iron and residue — both relevant to polymer colour and to catalyst behaviour downstream.

Common Process Problems & Likely Causes

When HMDA misbehaves in a plant, the cause is usually one of a short list of things. This table is the shortcut our technical desk works through before anyone opens a complaint file.

Packaging, Storage & Shipping

• Solution grade. 70% or 80% aqueous solution in 1000 L IBCs and bulk tanks — the practical choice for most users outside the polyamide plants.
• Molten bulk. Heated road tankers and heated ISO tank containers under nitrogen, for polyamide and isocyanate producers running continuously.
• Solid packing. Drums of crystalline material where the process needs anhydrous feed and melting is practicable.
• Melting and handling. HMDA is solid below about 42 °C. Heat gently and evenly and blanket the headspace — local overheating in contact with air darkens the product, and colour carries into polymer.
• Inert blanketing. Nitrogen-blanketed at fill where colour matters. The ethyleneamines darken on air contact more readily than most amines, and they also absorb carbon dioxide to form carbamate.
• Materials of construction. Stainless steel or suitable lined vessels. Avoid copper, brass, bronze, aluminium and mercury.
• Shelf life. Typically 12 months in unopened original packing under those conditions. Beyond that, re-test rather than assume.
• Transport classification. UN 1783, Hexamethylenediamine solution, Class 8 corrosive; or UN 2280, Hexamethylenediamine solid, Class 8 corrosive. Packing group depends on concentration — confirm against the current SDS for your destination and mode.

Hazards & Safe Handling

Hexamethylenediamine is corrosive and a skin sensitiser. It must be handled by trained personnel under a proper risk assessment. The classifications below are indicative — the current SDS supplied with your consignment is the governing document.

• Sensitisation. The ethyleneamines are recognised skin sensitisers, and several are respiratory sensitisers as well. Once a worker is sensitised, exposures previously tolerated can provoke a reaction, so preventing first contact matters far more than managing repeat contact. This is the dominant occupational concern across this whole family.
• Exposure control. Handle in a closed system or under local exhaust ventilation. Where the material is warmed or sprayed, vapour and mist exposure rise sharply and need their own controls.
• PPE. Chemical-resistant gloves rated for amines, chemical goggles and face shield, and chemical-resistant clothing. Glove breakthrough time is worth checking rather than assuming.
• Mixed-system handling. In a two-part epoxy system the uncured mixture carries the hazards of both hardener and resin. Applicators handling mixed material need controls for both, which is often where site assessments fall short.
• Incompatibilities. Strong oxidising agents, strong acids, acid chlorides, nitrites and isocyanates — the amine-isocyanate reaction is violently exothermic. Also copper, brass, bronze and aluminium.
• Spill response. Contain, absorb with inert non-combustible material and collect in a labelled closed container. Ventilate. Do not wash to drain.
• Environment. Harmful to aquatic life. Do not allow to enter drains, surface water or groundwater. Dispose through a licensed chemical waste contractor.
• First aid. Remove contaminated clothing immediately, wash skin with plenty of water and soap, flush eyes for at least 15 minutes, and seek medical attention with the SDS to hand. Report any skin or breathing reaction, which may indicate developing sensitisation.
• Hot and molten material. Molten HMDA and heated storage introduce thermal burn risk and raise vapour and mist exposure considerably. Treat heated handling as a separate operation with its own controls.

Regulatory & Compliance Notes

Hexamethylenediamine is a long-established industrial chemical and is listed on the major national chemical inventories. Because obligations differ by territory, volume and use, the notes below are orientation rather than legal advice — confirm your own position with your regulatory adviser before importing.

• Inventory status. Listed on the principal chemical inventories in the major importing regions. Ask us for the inventory confirmation relevant to your destination country.
• Import registration. Several territories require the importer to hold a registration or notification before a consignment lands. Start that process early — it is the most common cause of delay at destination.
• Hazard communication. Supplied with an SDS compliant with the format applicable to your region, and labelled in line with the GHS classification for the product.
• Sensitiser classification. As a skin sensitiser, HMDA triggers specific labelling and, in several jurisdictions, exposure control obligations for workers handling it or systems containing it.
• Food-contact polyamide. Where the resulting nylon will contact food, the finished polymer and any residual monomer are subject to food-contact rules at destination. Those attach to the polymer rather than the monomer, but residual HMDA limits form part of them.
• Dangerous goods. UN 1783 for the solution or UN 2280 for the solid, both Class 8 corrosive, with the packing group depending on concentration. Declarations prepared for IMDG (sea) or IATA (air) as appropriate.

We Supply HMDA Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Hexamethylenediamine (HMDA) from India to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, dangerous-goods paperwork and freight so the material arrives ready to use.

• Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
• Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other Indian ports arranged where it suits the routing.
• Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and dangerous-goods declaration issued as a complete set.
• Flexible volumes. A single drum for laboratory qualification, through LCL consolidations, up to repeat full loads on a supply contract.
• Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.

Buying HMDA from Chelora

We are an independent sourcing and supply partner. For HMDA that means establishing whether the end use is polymer, because polymer grade is defined by by-product limits that a technical certificate will not even report — and the gap between the two grades is far wider than the assay suggests.

• Documentation on every lot. Batch-specific COA including the by-product profile, current SDS and TDS.
• Multiple forms. 70% solution, molten bulk and solid, matched to how your plant handles material.
• Samples before commitment. Trial quantities for polymerisation or formulation qualification ahead of a commercial order.
• Quantities. From IBC quantities through to heated bulk tank loads on contract supply.
• Export experience. Class 8 dangerous-goods documentation, packing and labelling handled for sea and road freight.
• Related intermediates. Adipic acid chemistry partners, EDA, DETA, IPDA, 1,3-propanediamine and the wider diamine range.

How ordering works

• Send the enquiry. Product, grade or specification, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
• We quote. Price, lead time, packing and a sample COA, normally within one working day.
• Sample and qualify. For first orders or critical applications, we send a trial quantity so your lab can sign off before you commit.
• Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
• Production and QC. Material allocated and released against a batch-specific COA, with a pre-shipment sample where the application calls for it.
• Ship and document. Packed, labelled and loaded with the full export and dangerous-goods document set, and tracked through to arrival.

Related Diamines & Polymer Intermediates

Buyers of HMDA usually source several of these alongside it. Consolidating them on one order cuts freight cost and gives you a single point of contact for documentation.