Trimethylolpropane (TMP): Alkyd Resins, UV Curing and PU Applications

Trimethylolpropane (TMP, CAS 77-99-6) — a trifunctional polyol used to build high-performance alkyd resins, UV-curable coatings and inks, polyurethane, and synthetic lubricants. This guide covers its properties, main applications, typical grades, and a practical procurement checklist.
Updated: October 2026 | HY Chem — Shanghai HaiYu Xinyun International Trade Co., Ltd.

Table of Contents

What Is Trimethylolpropane (TMP)?
Key Properties
Main Applications
Grades and Specifications
How to Source TMP: A Procurement Checklist
Frequently Asked Questions

Trimethylolpropane — almost always written TMP — is one of the most versatile small polyols in the resin and coatings industry. As a white crystalline flake or powder with three hydroxyl groups, it behaves as a "branch point" that chemists use to build stronger, more durable polymer networks. That single structural feature is what makes TMP valuable in fast-drying alkyd paints, in UV-curable inks and coatings, in polyurethane systems, and in high-temperature synthetic lubricants. For formulators and buyers, TMP is a quiet but essential raw material — and one where grade selection and documentation matter as much as price. This guide explains what TMP is, how it behaves, where it is used, and what to verify before ordering.

1. What Is Trimethylolpropane (TMP)?

TMP is the common name for 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, a symmetric trifunctional alcohol with the formula C₆H₁₄O₃ and a molecular weight of 134.17 g/mol. At room temperature it is a white, low-odor crystalline solid supplied as flakes or powder. Its defining feature is a central quaternary carbon bearing three primary hydroxyl groups — a structure that lets it react like a small molecule yet function like a crosslinking node in a polymer chain.

Why the three hydroxyls matter
• A trifunctional molecule introduces branching and crosslinking, raising hardness, solvent resistance, and film integrity versus difunctional diols.
• It raises the hydroxyl value of the resin, so less material is needed to reach a target crosslink density.

Because of that branching, TMP is chosen where toughness, chemical resistance, and a hard, durable finish are the selling point — not where the lowest raw-material cost is the only priority.

2. Key Properties

Property	Typical Value / Description
Appearance	White to off-white crystalline flakes or powder
Molecular formula / weight	C₆H₁₄O₃ / 134.17 g/mol
Functionality	Trifunctional (3 primary hydroxyl groups)
Hydroxyl value	~1240–1260 mg KOH/g
Melting point	~56–60 °C
Solubility	Moderately soluble in water; soluble in alcohols, esters, and many organic solvents; low volatility
Key advantage	Branching from three OH groups → harder, more chemical-resistant, faster-curing networks

Note: figures are typical industry ranges — always confirm against the supplier's TDS and the COA of the specific batch.

3. Main Applications

3.1 High-Performance Alkyd Resins (largest use)

This is the traditional and still largest outlet for TMP. Incorporating TMP into an alkyd raises the crosslink density of the dried film, which translates into faster surface drying, higher hardness, better water and alkali resistance, and superior gloss retention. TMP-based alkyds are specified for premium industrial and architectural coatings, automotive refinish and OEM topcoats, coil and can coatings, appliance finishes, and durable wood and traffic paints. For the acid component, formulators often pair TMP with isophthalic acid (IPA) to push weatherability and toughness further.

3.2 UV-Curable Coatings, Inks and Adhesives

TMP is the backbone of one of the most important reactive monomers in radiation curing: trimethylolpropane triacrylate (TMPTA), along with diacrylate and ethoxylated variants. These acrylates cure almost instantly under UV or electron-beam light, enabling low-VOC, solvent-free coatings, printing inks, and adhesives with hard, scratch- and chemical-resistant surfaces. You will find them in wood and flooring coatings, overprint varnishes, conformal coatings, 3D-printing resins, and nail-care products. The three acrylate groups give TMPTA a very high crosslink density — which is exactly why it is a workhorse monomer across the UV-curing industry.

3.3 Polyurethane Systems

As a triol, TMP acts as a crosslinker and chain extender in polyurethane — improving the hardness, abrasion resistance, and chemical resistance of PU coatings, elastomers, rigid foams, and water-based polyurethane dispersions (PUD). It is a common choice where a formulator needs more crosslink density than a simple diol such as neopentyl glycol (NPG) can provide.

3.4 Synthetic Lubricants and Esters

Esterified with fatty or branched acids, TMP becomes a polyol ester base stock for high-temperature lubricants — aviation and gas-turbine oils, refrigeration and compressor fluids, and premium greases. The ester linkage and branched backbone give excellent thermal and oxidative stability plus good low-temperature behavior. Smaller outlets include plasticizers, rosin esters, and specialty alkyd modifiers. See our related guide: Neopentyl Glycol (NPG): Powder Coatings, Polyester Resins and Sourcing.

4. Grades and Specifications

TMP is not a single product — the right grade depends on your process and end use. The main axes of differentiation are:

Dimension	Options	Typical Fit
Physical form	Flake vs. powder	Flake for bag/jumbo packing; powder where a dust-free or fast-dissolving feed is preferred
Purity / grade	Standard (≥98.5%) vs. high-purity (≥99%)	High-purity preferred for clear, light-colored and UV-acrylate grades
Key specs	Assay, moisture, color (APHA), hydroxyl value, ash, acidity	Tighter color and moisture for exterior, appliance, and acrylate grades
Packaging	25 kg bags, 500/1000 kg jumbo bags	Chosen by order size and handling equipment

Selection tip: tell your supplier the end use (alkyd / UV acrylate / PU / lubricant), the required form (flake or powder), and any color or moisture limits. Those three points narrow the grade far faster than scanning a spec sheet.

5. How to Source TMP: A Procurement Checklist

Name the grade, not just "TMP". Specify form (flake/powder), target purity, and any color/moisture limits your process requires.
Request the documents. A serious supplier provides TDS (technical data sheet), COA (batch-specific certificate of analysis), and SDS/MSDS.
Trial before scaling. Run a small lab or pilot batch on your actual formulation — cure speed, compatibility, and film properties vary between grades more than the numbers suggest.
Check packaging and storage. TMP is hygroscopic; confirm net weight, liner type, and that material is kept dry and away from heat in transit and storage.
Clarify lead time and customs paperwork. For imports you will need commercial invoice, packing list, COA and SDS — confirm these ship with the cargo.
Verify export experience. A partner who regularly ships to your region understands packaging, labeling, and documentation, which reduces the risk of hold-ups.

6. Frequently Asked Questions

Is TMP the same as neopentyl glycol (NPG)?

No. NPG is a difunctional diol (two OH groups) prized for hydrolytic and weather stability in polyesters, while TMP is a trifunctional triol (three OH groups) that adds crosslinking, hardness, and faster curing. They are complementary, not interchangeable.

What is TMPTA, and why is it linked to TMP?

TMPTA (trimethylolpropane triacrylate) is made by reacting TMP with acrylic acid. Its three acrylate groups give UV-curable formulations a very high crosslink density, which is why TMPTA is one of the most widely used monomers in UV inks, coatings, and adhesives.

What is the smallest order quantity?

MOQ depends on grade and packaging. Sample quantities for lab evaluation are typically available, while bulk is quoted per tonne or per container. We focus on small-to-medium buyer orders in the 1–200 tonne range.

How is TMP shipped and stored?

TMP ships in sealed bags or jumbo bags kept dry. Store in a cool, dry, well-ventilated area away from heat and moisture, and reseal partially used containers promptly. Although it is a low-hazard solid, follow the SDS for dust control and routine industrial hygiene.

Need TMP samples, bulk quotes, or technical documents (TDS / COA / SDS)?
HY Chem supplies Trimethylolpropane and a full range of polyols and resin raw materials to manufacturers across Asia, the Middle East and Central Asia. Send us your target grade and application, and our team will reply within one business day.
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Column: Industry Information | Product: Trimethylolpropane (TMP) | Related: Neopentyl Glycol (NPG) / Isophthalic Acid (IPA) / Alkyd & Polyester Resins

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