Hexamethylenetetramine (Hexamine) CAS 100-97-0

What is Hexamethylenetetramine (Hexamine)?

Hexamethylenetetramine is structurally unlike every other amine in this range. Rather than a chain or a simple ring, it is a rigid three-dimensional cage — four nitrogens at the corners of a tetrahedron, bridged by six methylene groups, giving the adamantane-like structure C₆H₁₂N₄.

That caged geometry has an unusual consequence: all four nitrogens are tertiary, so hexamine has no N-H bond at all and is remarkably stable as a solid. It is a white crystalline powder with no melting point in the ordinary sense — heated, it sublimes and decomposes above about 280 °C rather than melting.

The decomposition is the point. Under heat or in acidic conditions the cage breaks apart and releases formaldehyde and ammonia. That makes hexamine a convenient solid, stable, easily weighed source of formaldehyde — which is why it is the standard hardener for novolac phenolic resins, where a formaldehyde donor is needed that can be dry-blended into a powder and will only release on cure.

Commercially, phenolic resin curing is the largest outlet, with foundry shell moulding, rubber compounding and a long tail of other applications behind it. Hexamine is also a pharmaceutical in its own right and a food preservative in a small number of jurisdictions. Buyers should be aware that it is a regulated explosives precursor in several territories, so documentation requirements are heavier than for an ordinary resin additive.

Why hexamine specifically

• A solid formaldehyde donor. Stable and easily weighed as a powder, releasing formaldehyde and ammonia only on heating or in acid — which is exactly what dry-blended novolac curing needs.
• No N-H and no melting point. All four nitrogens are tertiary and the cage sublimes rather than melts, giving unusual stability for a reactive amine.
• Dry-blendable. Being a free-flowing powder it mixes into solid resin systems in a way no liquid formaldehyde source can.
• Multiple industrial roles from one property. Resin hardener, rubber methylene donor, foundry binder component and corrosion inhibitor all stem from the same controlled formaldehyde release.

How Hexamine is Manufactured

Hexamine is made by one reaction, and it is an old and simple one: formaldehyde plus ammonia. The cage assembles itself.

• Condensation. Formaldehyde solution is reacted with ammonia, usually in aqueous phase at controlled temperature and pH. Six molecules of formaldehyde and four of ammonia condense with loss of water to form the cage spontaneously — the structure is thermodynamically favoured, which is why the synthesis is so straightforward.
• Concentration and crystallisation. The solution is concentrated under vacuum and the hexamine crystallises out. Vacuum is used because the product decomposes at the temperatures atmospheric evaporation would require.
• Drying. Crystals are separated and dried under controlled conditions. Over-drying at high temperature causes decomposition and discolouration, so drying temperature is a genuine process control rather than a formality.
• Grading. Material is sieved and graded. Particle size matters in dry-blend applications, where the hardener has to disperse evenly through a powdered resin, so technical grades are specified on granulometry as well as purity.

Typical Commercial Specification

Figures below are representative of technical commercial grade. Resin, rubber and pharmacopoeial grades with tighter limits and defined particle size are available — send us the specification you work to and we will quote against it.

Physical & Chemical Properties

Reactivity in practice

Hexamine's chemistry is almost entirely about controlled release and mild base action. Four behaviours cover its commercial use:

• Thermal formaldehyde release. Heated in a resin system, the cage decomposes and liberates formaldehyde, which crosslinks a novolac resin into a cured thermoset. The release is the function.
• Methylene donation in rubber. In rubber-to-textile and rubber-to-metal bonding systems it supplies methylene groups to react with a resorcinol-type acceptor, building an in-situ resin that bonds the two.
• Acid scavenging and pH buffering. As a weak base it neutralises acid and is used to inhibit acid corrosion, notably in pickling and acidising formulations.
• Salt formation. Forms salts with acids, including the hippurate and mandelate used medicinally as urinary antiseptics, which release formaldehyde only in acidic urine.

Hexamine vs Other Formaldehyde Donors and Curing Agents

Where a novolac resin or a rubber bonding system needs formaldehyde, the question is how to deliver it: as a liquid, as a polymer, or locked in a cage that only opens on heating. The answer usually comes down to whether the system is dry-blended and how much control over release temperature is needed.

Stated plainly: hexamine wins wherever the system is a dry powder and the formaldehyde must stay locked up until cure. Paraformaldehyde releases more readily, which can be an advantage or a storage liability depending on the process. Liquid formaldehyde is a non-starter in a dry blend and carries a direct exposure problem. And a resole resin avoids the question by having the formaldehyde built in, at the cost of limited shelf life.

Industries We Supply Hexamine To

The same powder leaves our warehouse for very different factories. What changes between them is the grade, the particle size, and — importantly for this product — the precursor documentation the destination requires.

Where Hexamine is Used

Hexamine's applications almost all exploit the same property: a stable solid that releases formaldehyde on demand. These are the end uses our customers buy it for.

As a novolac resin hardener

This is the dominant application. A novolac phenolic resin is made with a deficiency of formaldehyde, so it is a stable thermoplastic that will not cure on its own — it needs more formaldehyde supplied at the moment of moulding. Hexamine solves that elegantly: it is a free-flowing powder that can be dry-blended into the resin and stored indefinitely, and it releases formaldehyde and ammonia only when the moulding heat reaches it. The ammonia released also catalyses the crosslinking. Typical loadings are around a tenth of the resin weight, and particle size matters because the hardener has to disperse evenly through a solid.

In foundry shell moulding

Shell moulding coats sand with a novolac resin and hexamine, then blows it against a heated pattern. The heat melts the resin, releases the formaldehyde from the hexamine and cures a thin shell that is stripped off as a mould. It is a high-precision casting process and the resin-coated sand is a specified consumable, so consistency of the hexamine — particle size, free formaldehyde and moisture — directly affects shell strength and stripping behaviour.

In rubber bonding systems

Bonding rubber to steel cord or textile is done with a resin formed in situ during vulcanisation: a methylene donor and a methylene acceptor react within the compound to build a resin network at the interface. Hexamine is one of the standard donors, used with a resorcinol-type acceptor and silica. These systems are fundamental to tyre and hose construction. Compounders should note that the free formaldehyde released during mixing and curing is an occupational exposure to manage.

As a pharmaceutical and preservative

Hexamine salts — the hippurate and the mandelate — are long-established urinary antiseptics. The mechanism is elegant: the compound is excreted unchanged and only decomposes to release formaldehyde in acidic urine, delivering the antibacterial agent exactly where it is needed. Hexamine is also permitted as a food preservative in a small number of jurisdictions for specific products. Both uses need pharmacopoeial or food-grade material and come under medicines or food legislation rather than chemical control.

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 — titration against standardised acid after controlled hydrolysis, the standard method for this product.
• Free formaldehyde — colorimetric or chromatographic determination. The single most important quality figure, and an occupational one as well.
• Free ammonia — distillation and titration. Affects odour, pH and cure behaviour.
• Moisture — loss on drying or Karl Fischer. Closely linked to free formaldehyde, since damp storage accelerates decomposition.
• Particle size distribution — sieve analysis. Critical in dry-blend applications where even dispersion through a powdered resin determines cure uniformity.
• Ash and metals — residue on ignition, heavy metals and iron, which matter in pharmaceutical and electrical-grade resin service.

Common Process Problems & Likely Causes

When hexamine 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

• Standard packing. 25 kg net in multi-wall paper bags with a polyethylene liner, palletised and shrink-wrapped.
• Bulk packing. 500 kg and 1000 kg jumbo bags for continuous users.
• Moisture barrier. Hexamine is slightly hygroscopic and damp storage accelerates decomposition to formaldehyde and ammonia. Liner integrity is not cosmetic — it protects the specification.
• Storage. Cool, dry, well-ventilated store away from acids, oxidisers and nitrates. Humidity control matters more than temperature, within reason.
• Dust and flammability. Hexamine is classified as a flammable solid and the powder can form a combustible dust cloud. Dust control, earthing and ignition source management apply in any handling or blending operation.
• Shelf life. Typically 24 months in unopened original packing under dry conditions. Beyond that, re-test free formaldehyde rather than assume.
• Transport classification. UN 1328, Hexamethylenetetramine, Class 4.1 flammable solid, Packing Group III — shipped with full dangerous-goods documentation.
• Security and records. As a regulated explosives precursor in several jurisdictions, hexamine consignments may require registration, record-keeping and suspicious-transaction reporting. Plan for that before the first delivery.

Hazards & Safe Handling

Hexamethylenetetramine is a flammable solid, a skin sensitiser and a source of formaldehyde on decomposition. It is also a regulated explosives precursor in several jurisdictions. 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.

• Formaldehyde release. The hazard that matters most in practice is not hexamine itself but the formaldehyde it releases on heating or in acid. In moulding, foundry and rubber operations that release happens deliberately, so formaldehyde exposure control — ventilation, enclosure, monitoring — is part of the process design, not an afterthought.
• Sensitisation. Hexamine is a skin sensitiser, and the formaldehyde it releases is a sensitiser too. Preventing first exposure matters more than managing repeat exposure.
• Combustible dust. The powder can form an explosible dust cloud. Dust extraction, earthing and bonding, and ignition source control apply to any handling, sieving or blending operation.
• Flammable solid. Classified as a flammable solid for transport and supply. Keep away from heat, sparks and open flame, and store away from oxidisers and nitrates.
• PPE. Chemical-resistant gloves, eye protection and, where dust is generated, appropriate respiratory protection. Add formaldehyde-rated protection for hot operations.
• Incompatibilities. Strong oxidising agents, strong acids, nitrates and nitrating agents. Acid contact liberates formaldehyde directly.
• Spill response. Collect mechanically without raising dust and place in a labelled closed container. Avoid generating a dust cloud. Do not wash to drain.
• First aid. Remove from exposure, wash skin with plenty of water, flush eyes for at least 15 minutes, move to fresh air if formaldehyde vapour has been inhaled, and seek medical attention with the SDS to hand.

Regulatory & Compliance Notes

Hexamine carries an unusual combination of regulatory dimensions: it is a regulated explosives precursor in several jurisdictions, a pharmaceutical, a food preservative in a few territories, and a source of formaldehyde — which is itself heavily regulated. The notes below are orientation rather than legal advice; confirm your own position with your regulatory adviser well before importing.

• Explosives precursor controls. Hexamine is a regulated explosives precursor in several jurisdictions, including under European explosives precursor legislation. Depending on the territory this can mean registration or licensing for supply to certain users, record-keeping obligations, and a duty to report suspicious transactions. Expect end-use declarations as a normal part of the purchase.
• Inventory status. Listed on the principal chemical inventories in the major importing regions. Ask us for the inventory confirmation relevant to your destination country.
• Formaldehyde release and workplace rules. Because hexamine releases formaldehyde on heating, downstream processes fall under formaldehyde exposure rules at destination, which have tightened in several jurisdictions. This affects your process design rather than the raw material specification, but it is worth factoring in early.
• Pharmaceutical and food use. Methenamine salts for medicinal use require pharmacopoeial grade and come under medicines legislation. Food preservative use is permitted in only a small number of jurisdictions for specific products — confirm before assuming it is available.
• Dangerous goods. UN 1328, Hexamethylenetetramine, Class 4.1 flammable solid, Packing Group III. Declarations prepared for IMDG (sea) or IATA (air) as appropriate.
• 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.

We Supply Hexamine Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Hexamethylenetetramine (Hexamine) 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 Hexamine from Chelora

We are an independent sourcing and supply partner. For hexamine that means two things before the commercial conversation is even useful: establishing what your destination requires on precursor controls, and settling the grade and particle size your process actually needs.

• Documentation on every lot. Batch-specific COA including free formaldehyde and particle size, current SDS and TDS.
• Precursor compliance support. Help assembling the end-use declarations and registrations your destination requires.
• Multiple grades. Technical, resin, rubber and pharmacopoeial grades with defined granulometry.
• Quantities. From a single 25 kg bag through to jumbo bags and full-container loads.
• Export experience. Class 4.1 dangerous-goods documentation, packing and labelling for sea and road freight.
• Related intermediates. Phenolic resin partners, EDA, piperazine, morpholine and the wider amine range from one supplier.

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 Amines & Resin Intermediates

Buyers of hexamine 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.