Introduction to TMAU (Tetramethylol Acetylenediurea)
Tetramethylol acetylenediurea (TMAU, CAS 5395-50-6) is a formaldehyde-based crosslinker, best known by its correct modern name: 1,3,4,6-tetrakis(hydroxymethyl)glycoluril, or tetramethylol glycoluril. It is a white crystalline solid built on a glycoluril (bicyclic diurea) core carrying four hydroxymethyl (methylol) groups, and it is used to crosslink and cure polymers and to confer durable-press, wrinkle-resistant and easy-care properties on textiles.
TMAU belongs to the family of methylol crosslinkers used in textile finishing, coatings, adhesives and paper. It is a formaldehyde-based product, which is central both to how it works and to how it must be handled and regulated. This article covers the correct structure and chemistry of TMAU, the glycoluril-based production route, its specification, applications, the comparison with the classic DMDHEU crosslinker, and its sourcing.
PolyBlueChem can supply TMAU (CAS 5395-50-6); see the product page for the current specification.
Chemical Identity and Structure
The name “acetylenediurea” is historical and misleading, and the most important thing to get right about TMAU is its actual structure. TMAU is not a molecule with a carbon-carbon triple bond: it is a glycoluril — a bicyclic diurea formed from glyoxal and two urea units — carrying four N-hydroxymethyl groups. Its correct systematic name is tetrahydro-1,3,4,6-tetrakis(hydroxymethyl)imidazo[4,5-d]imidazole-2,5(1H,3H)-dione.
| Property | Value |
|---|---|
| Common name | Tetramethylol acetylenediurea (TMAU) |
| Correct chemical name | 1,3,4,6-Tetrakis(hydroxymethyl)glycoluril (tetramethylol glycoluril) |
| CAS number | 5395-50-6 |
| Molecular formula | C8H14N4O6 |
| Molecular weight | 262.22 g/mol |
| Core | Glycoluril (bicyclic imidazo[4,5-d]imidazole-2,5-dione) |
| Functional groups | Four N-hydroxymethyl (methylol) groups |
Two consequences follow from the structure. First, the four methylol groups are the reactive sites: they are what make TMAU a crosslinker. Second, there is no acetylenic triple bond, so descriptions of TMAU as a “reactive alkyne” are simply wrong; the reactivity comes from the methylol groups and the urea nitrogen atoms.
Physical and Chemical Properties
| Property | Typical value / behaviour |
|---|---|
| Appearance | White to off-white crystalline solid |
| Melting point | Approx. 137–138 °C |
| Density | Approx. 1.70 g/cm³ |
| Solubility in water | Sparingly soluble (the methylol groups give some water affinity) |
| Solubility in organics | Sparingly soluble in chloroform, DMSO and methanol |
| Stability | Stable when dry; can release formaldehyde and decompose under strong acid/base or heat |
| Hazard (GHS) | GHS07; H302 (harmful if swallowed), H315/H319 (skin/eye irritation), H335 (respiratory irritation) |
Because the molecule carries four methylol groups and is a formaldehyde-derived product, TMAU is handled as a reactive, formaldehyde-releasing solid, and its storage and processing conditions reflect that.
What Is “Acetylenediurea”? Clearing Up the Name
The old name “acetylenediurea” survives from an earlier era, when the condensation product of glyoxal with urea was drawn as an acetylene-bridged diurea. The compound was later shown to be the bicyclic glycoluril, so the true structure has no triple bond. This matters practically:
- It tells you what the feedstock is. The industrial route starts from glyoxal and urea (which give glycoluril), not from acetylene.
- It tells you where the reactivity lies. Reactivity is in the four methylol groups, not in any alkyne.
- It tells you the right specification. Buyers and regulators refer to the substance as tetrakis(hydroxymethyl)glycoluril.
Using the correct structure avoids the errors that appear in older descriptions: the wrong molecular formula (C8H14N4O6, not a C6 formula) and the wrong synthesis (urea and glyoxal, not urea and acetylene gas).
Chemistry of the Methylol Groups
The four N-hydroxymethyl groups are the heart of TMAU’s function. They are formed by reacting the N-H groups of glycoluril with formaldehyde, and they can react further in ways that build cross-linked networks:
- Condensation with hydroxyl groups. The methylol groups condense with hydroxyl groups on cellulose (in textiles), or with hydroxyl- and amide-functional polymers, forming ether or methylene bridges and cross-linking the substrate.
- Self-condensation. Methylol groups can also condense with each other or with the urea nitrogens, building a cured network.
- Acid-catalysed curing. The crosslinking is normally catalysed by an acid (or a latent acid) and driven by heat, which is how textiles and coatings are cured.
- Formaldehyde release. Under heat, acid or hydrolysis, methylol crosslinkers such as TMAU can release formaldehyde, a key consideration for formulation and regulation.
This chemistry places TMAU in the same family as the classic textile crosslinker DMDHEU (dimethyloldihydroxyethyleneurea), with which it competes and is often compared.
Industrial Production
TMAU is made in two principal steps: first the formation of glycoluril from urea and glyoxal, then the methylolation of glycoluril with formaldehyde.
| Stage | Purpose | Notes |
|---|---|---|
| 1. Glycoluril formation | Build the bicyclic diurea core | Urea + glyoxal condensation gives glycoluril (the “acetylenediurea” core) |
| 2. Methylolation | Add four hydroxymethyl groups | Glycoluril + formaldehyde (about 4 mol equivalents) under mildly alkaline conditions |
| 3. Reaction control | Complete the methylolation | pH held mildly alkaline (for example around pH 8, adjusted with NaOH); gentle heating |
| 4. Isolation | Recover the solid | Concentration and precipitation (for example with methanol) followed by filtration and drying |
| 5. Quality control | Confirm the specification | Assay, melting point, free formaldehyde and moisture |
A representative process reacts an aqueous formaldehyde solution with glycoluril at mildly alkaline pH (from about 40 up to about 55 °C), concentrates the solution, and precipitates the product with methanol to give tetrakis(hydroxymethyl)glycoluril in high yield. Because the feedstock is formaldehyde, process safety and emission control are central to production.
Specifications and Quality Control
TMAU is defined by its assay, its physical constants and its free-formaldehyde content, the last being the key parameter for products that must meet formaldehyde limits.
| Parameter | Typical specification |
|---|---|
| Appearance | White to off-white crystalline solid |
| Assay (active content) | Typically 98% or higher, grade-dependent |
| Melting point | Approx. 137–138 °C |
| Free formaldehyde | Controlled to meet customer/regulatory limits |
| Moisture | Low; the solid is stored dry |
| Solubility (in the intended vehicle) | For solution use, checked to ensure clean dissolution |
Free formaldehyde is the parameter that most distinguishes TMAU grades for sensitive applications, and it is also an environmental and occupational-health concern in both production and use.
Grades and Forms
- Solid (crystalline). The standard form described here; a white solid.
- Aqueous solutions. Supplied as solutions for ease of dosing into textile and coating baths.
- Formulated crosslinker systems. Blend-compatible with catalysts, softeners and other finishing agents for textile finishing.
- Low-free-formaldehyde grades. For customers targeting lower formaldehyde release.
Applications: Textile Finishing
The classic use of TMAU is textile finishing, where it is applied to cellulosic fabrics (above all cotton) to give durable-press, wrinkle-resistant, “easy-care” properties. The methylol groups condense with the hydroxyl groups of cellulose under acid catalysis and heat, forming covalent cross-links that hold the fibres in place and prevent the wrinkling and shrinking that untreated cotton suffers.
| Benefit | Mechanism |
|---|---|
| Wrinkle resistance / durable press | Cross-links prevent fibre slippage |
| Dimensional stability | Cross-linking limits shrinkage on washing |
| Easy-care / minimum iron | Fabric holds its shape after laundering |
| Improved wet and dry crease recovery | Cellulose is locked in shape |
TMAU is valued in this application for the balance of performance and formaldehyde release: as a glycoluril-based crosslinker it can offer lower formaldehyde release than the older DMDHEU systems, which matters as textile formaldehyde limits tighten worldwide. It is typically applied with an acid or latent-acid catalyst in a pad-dry-cure process.
Applications: Coatings, Adhesives and Paper
Beyond textiles, TMAU functions as a crosslinker for polymers used in coatings, adhesives and paper, where its four methylol groups build network density and improve performance.
- Coatings. Cross-linking of hydroxyl- or amide-functional resins improves hardness, chemical and water resistance, and durability, and contributes to the cure of certain waterborne and powder systems.
- Adhesives. As a curing/crosslinking agent that raises cohesive strength, heat resistance and water resistance in suitable resin systems.
- Paper and board. As a wet-strength or binder crosslinker in paper treating, improving strength and wet performance.
As in textiles, the crosslinking is cured with heat and usually an acid catalyst, and the formaldehyde-releasing nature of the chemistry is managed through formulation and process control.
Other Applications
- Concrete and construction. Glycoluril derivatives are used as components of concrete admixtures.
- Biocidal / functional additives. Some glycoluril chemistry finds use in antimicrobial or functional formulations; these uses are niche and market-specific.
- Crosslinker for functional polymers. Any polymer carrying hydroxyl, amide or similar groups can, in principle, be crosslinked with a methylol crosslinker such as TMAU, so the application set continues to expand.
TMAU vs DMDHEU and Other Crosslinkers
TMAU competes with the classic textile crosslinkers. The table compares the main options.
| Crosslinker | Chemistry | Performance | Formaldehyde release |
|---|---|---|---|
| TMAU (tetramethylol glycoluril) | Glycoluril core + 4 methylol groups | Good durable-press; robust crosslinking | Moderate; can be lower than DMDHEU in some systems |
| DMDHEU | Dimethyloldihydroxyethyleneurea | Benchmark durable-press performance | Higher unless “low-formaldehyde” grade |
| Low-formaldehyde DMDHEU | Etherified/modified DMDHEU | Balanced performance and low release | Low |
The trend in textile finishing is toward lower formaldehyde release, which has made glycoluril-based crosslinkers such as TMAU and the etherified DMDHEU grades increasingly attractive. Specialised crosslinkers are sometimes blended to balance cost, performance and formaldehyde release.
Formulation, Curing and Handling
- Catalysis and curing. Methylol crosslinking is acid-catalysed and cured with heat; the catalyst, pH and curing schedule are matched to the substrate and the target properties.
- Dosing. In textile baths, TMAU is applied with a catalyst and often a softener; in coatings and adhesives it is dosed into the resin system.
- Dissolution. The solid is dissolved (or a supplied solution is used) to give a clean bath free of undissolved particles.
- Formaldehyde control. Because the chemistry releases formaldehyde, ventilation, emission control and, where applicable, low-formaldehyde grades are important.
- Storage. Keep sealed, cool and dry; avoid strong acids, bases and excessive heat, which can cause decomposition and formaldehyde release.
Safety, Health and Environment
- Formaldehyde. TMAU is formaldehyde-based and can release formaldehyde; formaldehyde is a skin/respiratory sensitiser and a known carcinogen, so exposure must be controlled. Use local exhaust ventilation and appropriate PPE, and follow the SDS.
- Irritancy and ingestion. The solid carries hazard statements for harm if swallowed and for skin, eye and respiratory irritation; avoid dust generation and contact.
- Environment. Prevent release to drains and watercourses; manage waste in line with local regulations.
- Documentation. Work from the SDS and confirm the free-formaldehyde level and any regulatory statements for your market.
Regulatory Status
Because TMAU is a formaldehyde-based crosslinker, its regulation is dominated by formaldehyde.
- Textile formaldehyde limits. Many markets set maximum free-formaldehyde or released-formaldehyde limits on finished textiles, which drives the choice between TMAU, DMDHEU and low-formaldehyde grades.
- Industrial chemicals. TMAU is registered as an industrial chemical in major markets (for example REACH in the EU, TSCA in the US).
- Documentation. Buyers should require the SDS, per-batch COA with free-formaldehyde data, and any market-specific compliance statements.
Market and Supply Overview
- Demand drivers. Textile finishing (especially durable-press and easy-care cotton) and industrial crosslinking in coatings, adhesives and paper.
- Production base. Made by a limited number of fine-chemical and textile-auxiliary producers.
- Price drivers. The cost of glyoxal, urea and formaldehyde feedstocks, and process energy.
- Quality differentiators. Assay, free formaldehyde, colour and solubility.
- Packaging. Sealed drums or bags for the solid, or drums/IBCs for solutions.
Procurement and Sourcing Guide
- Confirm the identity. TMAU is tetramethylol glycoluril (CAS 5395-50-6); be wary of descriptions referring to an acetylene triple bond.
- Assay and free formaldehyde. Check both; free formaldehyde is the key regulatory and performance parameter.
- Form. Solid or solution, matched to your process.
- Grade and catalyst compatibility. Confirm the grade suits your catalyst and curing system.
- Documentation. Require an SDS, a per-batch COA and regulatory statements.
PolyBlueChem can supply TMAU (CAS 5395-50-6). To request current specifications, a COA or a quotation, contact the PolyBlueChem team.
How Durable-Press Finishing Works
Durable-press and easy-care finishing of cotton is the classic application of TMAU, and understanding the process explains why the crosslinker is chosen. Cotton is cellulose: long polymer chains of glucose units, studded with hydroxyl groups, held together by hydrogen bonds. When cotton is washed and dried, those chains slip past one another and reform hydrogen bonds in new positions, which is why untreated cotton wrinkles and shrinks.
A methylol crosslinker such as TMAU interrupts this. In the presence of an acid catalyst and heat, its methylol groups condense with the cellulose hydroxyls, forming covalent cross-links between adjacent chains. Once cross-linked, the chains can no longer slip, so the fabric resists wrinkling and holds its shape through washing.
| Step | What happens |
|---|---|
| Pad | Fabric is passed through a bath of crosslinker, catalyst and softener, then squeezed to a controlled wet pick-up |
| Dry | Fabric is dried, removing water and bringing reactants into contact |
| Cure | Heat and acid catalyst drive the condensation between methylol groups and cellulose hydroxyls, forming cross-links |
| Wash/rinse | Unreacted chemicals are removed, reducing residual formaldehyde and improving the hand |
The crosslinker’s chemistry affects several outcomes: the degree of wrinkle recovery, the loss of strength (crosslinking can embrittle cotton), the hand of the fabric, and the formaldehyde release. TMAU’s glycoluril chemistry offers a balance of these factors, which is why it appears alongside DMDHEU in commercial finishing.
Formaldehyde: The Central Issue for Methylol Crosslinkers
Because TMAU is a methylol (formaldehyde-based) crosslinker, formaldehyde is the issue that shapes its use, its regulation and its competition with alternatives.
- Where it comes from. Free formaldehyde can be present in the product, and more can be released when the methylol groups react and when the finished material is heated or hydrolysed.
- Why it matters. Formaldehyde is a respiratory and skin sensitiser and a known carcinogen; occupational exposure and consumer exposure from finished goods are both regulated.
- How it is managed. Producers and finishers control free formaldehyde in the crosslinker, use efficient curing and washing to reduce residuals, and increasingly choose lower-release crosslinker chemistries.
- How the market responds. The trend toward lower formaldehyde release is the main force pushing textile finishers from classic DMDHEU toward glycoluril-based crosslinkers such as TMAU and toward etherified, low-formaldehyde grades.
For a buyer, this means the free-formaldehyde figure on the specification is not just a quality number — it is a compliance and market-access number, and it should be confirmed for the intended end use and market.
Crosslinkers Beyond Textiles: Why Glycoluril Chemistry Is Useful
Glycoluril-based crosslinkers are attractive outside textiles for the same structural reason they work inside them: the rigid bicyclic glycoluril core, functionalised with reactive methylol groups, builds cross-link density efficiently. In coatings and adhesives this translates into faster property development (hardness, chemical resistance, water resistance) at relatively low addition levels, and into crosslinks that are thermally robust. The availability of the solid and of aqueous solutions lets the same chemistry be used in solvent-borne, waterborne and powder systems with appropriate formulation, which is why glycoluril crosslinkers appear across a range of industrial coatings.
Frequently Asked Questions
What is TMAU and what is its CAS number?
TMAU is tetramethylol acetylenediurea, correctly named 1,3,4,6-tetrakis(hydroxymethyl)glycoluril — a formaldehyde-based crosslinker; its CAS number is 5395-50-6. See the product page for specifications.
What is the molecular formula of TMAU?
C8H14N4O6, with a molecular weight of 262.22 g/mol.
Does TMAU contain a triple bond?
No. Despite the historical name “acetylenediurea”, TMAU has a glycoluril (bicyclic diurea) core and no carbon-carbon triple bond; the reactivity comes from its four hydroxymethyl groups.
How is TMAU made?
From urea and glyoxal (which form glycoluril), followed by methylolation with formaldehyde under mildly alkaline conditions.
What is TMAU used for?
Mainly as a crosslinker in textile finishing (durable-press, wrinkle-resistant cotton), and in coatings, adhesives and paper; also in concrete admixtures.
Does TMAU release formaldehyde?
Yes; it is a formaldehyde-based methylol crosslinker, so formaldehyde release is a formulation, handling and regulatory consideration.
How does TMAU compare with DMDHEU?
Both are methylol crosslinkers for textiles. TMAU’s glycoluril chemistry can offer lower formaldehyde release in some systems, while DMDHEU is the classic benchmark. See the comparison above.
How should TMAU be stored?
Sealed, cool and dry, away from strong acids, bases and heat, which can cause decomposition and formaldehyde release.
Is TMAU the same as glycoluril?
No. Glycoluril is the core bicyclic diurea; TMAU is glycoluril with four hydroxymethyl (methylol) groups added. Glycoluril is the starting material, TMAU the finished crosslinker.
What industries use TMAU?
Primarily textile finishing (durable-press and easy-care cotton), plus coatings, adhesives, paper treating and some construction admixtures.
Is TMAU a low-formaldehyde crosslinker?
Its glycoluril chemistry can give lower formaldehyde release than classic DMDHEU in some systems, but it is still a formaldehyde-based product; the free-formaldehyde figure and the release behaviour are the parameters to confirm.
Can TMAU be used in powder coatings?
Glycoluril crosslinkers are used in certain powder-coating systems; the suitability depends on the specific formulation and curing conditions.
What are typical uses of TMAU crosslinker?
Durable-press and easy-care finishing of cotton, and crosslinking of coatings, adhesives and paper; it can also feature in certain concrete admixtures.
Does TMAU need a catalyst?
Yes. Its methylol crosslinking is acid-catalysed (or latent-acid catalysed) and cured with heat, so the catalyst and cure schedule are part of the formulation.
References and Disclaimer
References. Substance identification data for tetramethylol acetylenediurea / tetrakis(hydroxymethyl)glycoluril (CAS 5395-50-6); standard chemistry of glycoluril, methylol crosslinkers and textile durable-press finishing; manufacturer technical data. Specifications quoted are representative and should be confirmed against the current certificate of analysis.
Disclaimer. This article is provided for general technical and commercial information only and does not constitute a specification or a warranty of fitness for any particular use. Users are responsible for confirming regulatory status, safe handling and suitability of the material for their own application and market.