1,3-Benzenediamine · 1,3-diaminobenzene · m-PDA · Flakes and molten supply
m-Phenylenediamine is the simplest aromatic diamine there is — a benzene ring with two amino groups in the meta positions, and nothing else. That bare structure gives it the lowest amine hydrogen equivalent weight of any common aromatic hardener, which is why a little goes a long way in epoxy. It is also the diamine half of meta-aramid fibre and of the polyamide skin on virtually every reverse osmosis membrane in service. Unlike most of the diamines on this page, it is not a category 1B carcinogen — the handling case here is acute toxicity, skin sensitisation and aquatic hazard. Chelora Amines supplies MPD in flake and molten form, with a batch-wise COA and SDS on every dispatch.
72.07 + 8.06 + 28.01 = 108.14 g/mol
m-Phenylenediamine — 1,3-benzenediamine, 1,3-diaminobenzene, m-PDA — is a benzene ring carrying two primary amino groups three positions apart. It is a white to pale tan crystalline solid melting at about 63 °C, which is low enough that it handles molten at modest temperature. Fresh material is nearly colourless; it darkens to red-brown faster than almost any other diamine on exposure to air and light.
Three applications dominate. As an epoxy curing agent it has been the reference aromatic hardener for decades, giving a Tg well above 150 °C at a mix ratio of only about 14 parts per hundred of resin. As a polyamide monomer it reacts with isophthaloyl chloride to give meta-aramid fibre, and with trimesoyl chloride at an oil–water interface to give the thin polyamide layer that does the actual separating in reverse osmosis and nanofiltration membranes. And as a dye intermediate it sits behind a long list of azo, direct and basic colourants.
Its hazard profile is different from the other diamines in this category. MPD is not classified as a category 1B carcinogen. It is acutely toxic by all three routes, a skin sensitiser, a suspected mutagen and very toxic to aquatic life — which means the controls that matter are glove discipline, splash protection and keeping it out of drains, rather than an authorisation regime.
| Chemical name | m-Phenylenediamine |
| Common synonyms | MPD, m-PDA, 1,3-benzenediamine, 1,3-diaminobenzene, 1,3-phenylenediamine |
| CAS number | 108-45-2 |
| EC / EINECS number | 203-584-7 |
| HS / HSN code | 2921 51 (phenylenediamines and diaminotoluenes; HSN 2921 51 on Indian invoices) |
| Molecular formula | C₆H₈N₂ (C₆H₄(NH₂)₂) |
| Molecular weight | 108.14 g/mol |
| Appearance | White to pale tan flakes or crystals; darkens rapidly to red-brown in air and light |
| Odour | Faint amine-like odour |
| Melting point | About 63–66 °C |
| Boiling point | About 282–287 °C at atmospheric pressure |
| Density | About 1.14 g/cm³ |
| Solubility in water | Freely soluble; also soluble in alcohols, ether and acetone |
| Amine value | About 1030–1040 mg KOH/g |
| Amine hydrogen equivalent weight | About 27.0 (four active hydrogens per molecule) |
| Flash point | About 157 °C (closed cup) |
| UN number | UN 1673, Phenylenediamines, Class 6.1, Packing Group III |
| Regulatory status | CLP Acute Tox. 3, Skin Sens. 1, Muta. 2, Aquatic Acute and Chronic 1; restricted in cosmetics |
Figures are typical values for the technical grade. High-purity and laboratory grade values may differ. All values for the material you order are stated on its Certificate of Analysis and Safety Data Sheet.
Two primary aromatic amines on the smallest possible backbone. Everything follows from that: high reactive-group density, high solubility and a kinked geometry that keeps the resulting polymers workable.
Each N–H adds across an epoxide ring, so one MPD molecule ties four chains together. With a molecular weight of only 108 the crosslink density is very high, which is where the thermal and chemical resistance comes from.
AHEW ≈ 27.0 · 4 active HMPD in water meets trimesoyl chloride in a hydrocarbon phase and polymerises at the interface in seconds, forming the ultra-thin crosslinked polyamide layer that does the separation in a composite membrane.
MPD(aq) + TMC(org) → polyamide filmLow-temperature polycondensation with isophthaloyl chloride gives poly(m-phenylene isophthalamide) — the flame-resistant, textile-processable aramid.
MPD + isophthaloyl chloride → aramidBoth amines diazotise and couple. Coupling MPD with its own diazonium salt gives the classic brown direct dyes, and the chemistry extends across a wide colourant range.
2 × ArNH₂ → bis-diazoniumReaction with aromatic dianhydrides gives poly(amic acid), cyclised thermally to a polyimide. The meta linkage keeps the precursor soluble and the film tractable.
MPD + dianhydride → polyimideReacts rapidly with isocyanates to give substituted ureas — too rapidly for open casting, but useful as an accelerator and in controlled prepolymer chemistry.
R–NCO + H₂N–Ar → ureaForms water-soluble salts with mineral and organic acids. The dihydrochloride is a common handling and purification form and appears in several analytical procedures.
MPD + 2 HCl → dihydrochlorideOxidises in air and light faster than most aromatic diamines, going from white through pink to deep red-brown. Reactivity is largely unaffected but colour-critical users must control exposure.
air + light → rapid darkeningMembrane and electronic-grade users work to much tighter limits than epoxy formulators — iron, chloride and isomer content all matter at parts-per-million level when the product is a film a hundred nanometres thick. If that is your application, send us the full specification rather than a purity figure, and we will tell you straight away whether we can meet it.
Discuss your processMPD is made by nitrating benzene twice and hydrogenating the result. The meta orientation is not a choice made later — it is set by the directing effect of the first nitro group.
Benzene is nitrated to nitrobenzene and then again with mixed acid. The nitro group is meta-directing, so the second nitro group lands predominantly at the 3-position.
Crude m-dinitrobenzene is purified by washing and crystallisation, removing the small quantities of ortho and para isomers formed alongside it.
Both nitro groups are hydrogenated over a supported catalyst to give crude m-phenylenediamine and water; the catalyst is separated and recycled.
Water and light ends are stripped and the product vacuum-distilled, removing aniline, residual isomers and heavies to take the assay above 99%.
Molten product is flaked or pastillated under nitrogen and bagged in a contained plant, or loaded hot into heated tankers for molten delivery.
p-Phenylenediamine is a different product with a different purpose, and the two are not interchangeable. Para substitution gives a straight, rigid chain — which is exactly what you want for para-aramid fibre and its extreme tensile modulus, and exactly what you do not want when the polymer has to be dissolved, spun into a textile fibre and dyed. The meta linkage puts a permanent kink in the backbone, keeping the polymer soluble and the fibre flexible. The same geometry matters in membranes, where a kinked, loosely packed polyamide network passes water while rejecting salt. If a specification calls for MPD, substituting the para isomer will not give a slightly different product — it will give a different material entirely.
MPD darkens faster than any other diamine we supply. Freshly distilled flake is white to very pale; left open to air and light it passes through pink to a deep red-brown within days. Amine value barely moves, so epoxy formulators can usually ignore it, but membrane, dye and electronic-grade users cannot — oxidation products are exactly the kind of impurity that shows up in a thin film. Keep packs sealed, opaque and cool, blanket molten storage with dry nitrogen throughout, and open only what you will use. In sealed, opaque packaging stored cool and dry, flake MPD normally holds specification for twenty-four months from manufacture.
The gap between an epoxy grade and a membrane grade is wider here than for most products. Assay, colour and trace metals decide which one you need.
Flake or pastille for epoxy curing agents, dye and pigment intermediates, resins and general synthesis.
Distilled, tightly specified on colour, aniline, isomers and trace metals for membrane casting, aramid and electronic-grade resins.
Highest purity for analytical, research and reference use, supplied in small sealed packs with full batch documentation.
| Parameter | Test method | Typical specification |
|---|---|---|
| Appearance | Visual | White to pale tan flakes or pastilles |
| Assay | GC | ≥ 99.0% w/w |
| o- and p-isomers, total | GC | ≤ 0.3% w/w |
| Free aniline | GC | ≤ 0.2% w/w |
| Solidification point | Crystallisation | ≥ 62.5 °C |
| Amine value | Potentiometric titration | 1030 – 1040 mg KOH/g |
| Colour, molten (APHA) | APHA / Hazen | ≤ 150 |
| Moisture | Karl Fischer | ≤ 0.3% w/w |
| Ash | Gravimetric | ≤ 0.05% w/w |
Indicative specification for planning. The controlling document is the Certificate of Analysis issued for your batch. Membrane, aramid and electronic-grade requirements are quoted against your own specification sheet.
An old hardener chemistry and a very modern membrane one, sharing the same molecule.
The reference aromatic hardener for filament winding, tooling, electrical laminates and chemically resistant linings — high Tg at the lowest mix ratio of the family.
Interfacially polymerised with trimesoyl chloride to form the thin-film composite polyamide layer in RO and nanofiltration elements for desalination and water treatment.
Polycondensed with isophthaloyl chloride to give poly(m-phenylene isophthalamide) for flame-resistant protective clothing, insulation paper and filtration felts.
Diazotised and coupled for azo, direct and basic dyes — including the classic brown direct colourants — for textiles, leather, paper and inks.
Condensed with aromatic dianhydrides for polyimide films, wire enamels, adhesives and composite matrices where the meta linkage keeps the precursor soluble.
An intermediate for aromatic Schiff bases, inhibitor packages and petroleum additives used in refining, pipelines and lubricant formulations.
Used in small quantities as an accelerator and crosslinker in adhesive, sealant and specialty urethane systems where fast amine reactivity is wanted.
A standard aromatic diamine in polymer chemistry, cure kinetics and membrane research, and an analytical reagent in several established methods.
From firefighter turnout gear to desalination plants — the value chain downstream of m-phenylenediamine.
| Derivative | Made by | End use |
|---|---|---|
| Thin-film composite polyamide | Interfacial polymerisation with trimesoyl chloride | Reverse osmosis and nanofiltration membrane elements |
| Poly(m-phenylene isophthalamide) | Low-temperature polycondensation with isophthaloyl chloride | Meta-aramid fibre, paper and felt for protective clothing and insulation |
| MPD-cured epoxy networks | Stoichiometric cure of epoxy resin at AHEW ≈ 27 | Filament-wound vessels, tooling, electrical laminates, linings |
| Azo, direct and basic dyes | Diazotisation and coupling of one or both amino groups | Textile, leather, paper and ink colourants |
| Polyimide and polyamide-imide resins | Condensation with aromatic dianhydrides | Films, wire enamels, adhesives and composite matrices |
| Schiff bases and inhibitor intermediates | Condensation with aldehydes and ketones | Corrosion inhibitors, petroleum additives, process chemicals |
| m-Phenylenediamine dihydrochloride | Salt formation with hydrochloric acid | Analytical reagent and a water-soluble handling form |
Every container carries the Chelora Amines label with product name, grade, net weight, batch number, manufacturing date, UN number and hazard pictograms. Packs are sealed under nitrogen, opaque, and designed to be opened once.
PE-lined, heat-sealed bags of flake or pastille product, or lined fibre drums where a rigid, fully opaque pack suits colour-sensitive use. Palletised and shrink-wrapped.
Lined FIBCs with a discharge spout for contained charging into a melt tank or dissolver, keeping dust exposure and air contact to a minimum.
Heated road and ISO tankers for continuous consumers — the low melting point keeps delivery temperatures modest; 100 g to 1 kg sealed containers for laboratory use.
Because MPD discolours so readily, pack size is worth thinking about. A 500 kg bag opened for a 40 kg batch leaves the balance exposed, and the colour will have moved by the time you come back to it. For colour-critical work, smaller sealed packs usually cost less in practice than a bulk pack and a rejected batch. Export consignments are packed in UN-specification packaging with full dangerous goods documentation and shipped FOB, CIF or CFR through Nhava Sheva and Mundra.
Plan my supplyMPD is toxic if swallowed, in contact with skin or if inhaled, may cause an allergic skin reaction, is suspected of causing genetic defects and is very toxic to aquatic life with long-lasting effects. It is absorbed through intact skin, and sensitisation is a real occupational risk for anyone handling it repeatedly. The notes below are a summary for planning only — always work to the Safety Data Sheet and your own site risk assessment.
Not for cosmetic use. m-Phenylenediamine and its salts appear in older hair dye literature and are restricted or prohibited in cosmetic products across the European Union and a number of other jurisdictions. We supply MPD for industrial and professional use only and do not supply it for cosmetic applications. If you are sourcing for personal care, tell us what you need the chemistry to do and we will point you at a compliant route.
Ask about alternatives| Parameter | Specification | Result |
|---|---|---|
| Appearance | White to pale tan flakes | Complies |
| Assay (GC) | ≥ 99.0% | Complies |
| o- and p-isomers, total | ≤ 0.3% | Complies |
| Solidification point | ≥ 62.5 °C | Complies |
| Colour, molten (APHA) | ≤ 150 | Complies |
| Moisture (KF) | ≤ 0.3% | Complies |
MPD is checked before dispatch. Each consignment leaves with the paperwork your QC, EHS, stores and accounts teams need on day one — including the amine value that sets your mix ratio and the colour figure that matters downstream.
Five steps for a first order of MPD. Grade selection in step two is where membrane and aramid users should spend their time.
Grade, quantity, flake or molten, your colour and impurity limits, how the material will be charged, and your delivery location.
We confirm the application and match it to technical, low-colour or laboratory grade — and against your own specification sheet where you have one.
We quote, then the batch is tested — assay, isomers, solidification point, colour and moisture — and the COA and SDS are prepared.
Sealed, nitrogen-blanketed, opaque packs move under dangerous goods documentation, or a heated tanker is loaded for molten delivery.
Material reaches your gate and repeat dispatches are scheduled to your usage, keeping stock fresh rather than sitting in your warehouse darkening.
Buyers who order MPD usually source these from the same list. See the full product range for the complete picture.
Short answers to what purchase, lab, EHS and plant teams ask us most. Anything else, ask us directly.
Send the grade, form, quantity, pack size, intended end use and your delivery address or destination port. We come back with a price, the documents that go with the batch and a dispatch or shipping plan, usually within 24 hours.