184 (CAS 947-19-3)
| CAS No. | 947-19-3 |
|---|---|
| Alias | Hydroxycyclohexyl phenyl ketone |
| Category | Photoinitiators |
| Purity | ≥98.00% (GC) |
| Packaging | 20kg/carton |
184 is a general-purpose free radical photoinitiator based on 1-hydroxycyclohexyl phenyl ketone. It offers excellent oxygen polymerization resistance, good thermal stability, and yellowing resistance. It is widely used in UV-curable systems and as a co-initiator in UV-curing ink formulations.
Equivalent grades. The same substance is sold by other manufacturers as Omnirad 184, Irgacure 184, Darocur 184. It is the same CAS number (947-19-3) and the same chemistry, so a formulation written around one of those grades transfers directly.
Introduction
Ask anyone who has run a UV line for a decade which photoinitiator they trust, and 184 comes up first. It is the benchmark alpha-hydroxy ketone, and it has held that position because of two properties that are hard to beat at the same time: it resists oxygen, and it does not yellow.
Oxygen inhibition is the race every surface cure has to win. Oxygen in the air quenches excited states before they can start a polymer chain, which is why so many formulations come out tacky at the surface. 184 wins that race more reliably than most, and that is why it stays specified in clearcoats, adhesives and laminating systems where a tacky surface is simply not acceptable. Cured films come out water-clear and stay that way under normal service.
Physical & Chemical Properties
White crystalline powder. Molecular formula C13H16O2, molecular weight 204.26, purity ≥98.00% by GC, melting range 45.0–50.0 °C, loss on drying ≤0.50%. Absorption maxima at 244, 280 and 330 nm.
Applications
Run it at 3–5% as the primary photoinitiator, or at 1–3% as a co-initiator alongside something with a longer absorption tail. A large share of the blends we ship pair it with TPO or ITX for exactly that reason: 184 carries the surface, the second initiator reaches the depth. Storage matters more than it looks. Light and humidity degrade it quietly, and you will not notice until cure times start to drift.
Regulatory status
184 has no harmonised classification under CLP. In August 2025 IGM Resins, whose Omnirad 184 is the same substance, issued a self-classification as Reprotoxic 1B and then withdrew it. There is no REACH restriction, no Candidate List entry, and no Annex XIV action on 184. Some SDS documents in circulation still carry the withdrawn classification, which is a paperwork lag rather than a change in the law. Ask your supplier for the current revision.
Handling & Storage
Keep sealed, cool and dark. Shelf life one year from production.
Packaging
20 kg cartons. COA with every batch, SDS available in English, samples for line trials on request.
Applications & Industries
Coatings & Paints
Metal driers (cobalt, manganese, zirconium octoate, naphthenates) and photoinitiators for coatings, paints, varnishes and industrial finishes — with COA & MSDS per batch.
UV Curing & Printing Inks
Free radical photoinitiators for UV-curable inks, coatings, adhesives and 3D printing — 1173, 184, 369, 907, ITX, DETX, TPO/TPO-L and liquid blends, QC-tested per batch.
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