| HS Code | 792453 |
| Chemical Name | 1-Hydroxycyclohexyl phenyl ketone |
| Cas Number | 947-19-3 |
| Molecular Formula | C13H16O2 |
| Molecular Weight | 204.27 g/mol |
| Appearance | White to off-white crystalline powder |
| Melting Point | 45-49 °C |
| Solubility | Soluble in common organic solvents (e.g., acetone, methanol, toluene); insoluble in water |
| Absorption Maxima | 244 nm and 280 nm (in methanol) |
| Type | Type I (cleavage) free radical photoinitiator |
| Typical Concentration | 1-5 wt% in UV-curable formulations |
| Applications | UV curing of coatings, inks, adhesives, and photopolymers |
As an accredited Photoinitiator BASF Irgacure 184 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Photoinitiator BASF Irgacure 184 is supplied as white crystalline powder in 20 kg fiber drums with inner polyethylene liner. |
| Container Loading (20′ FCL) | 20′ FCL: palletized drums of BASF Irgacure 184 photoinitiator, securely blocked, moisture-protected, and ventilated to prevent heat accumulation during transit. |
| Shipping | Ship as a solid chemical in sealed, moisture-proof polyethylene-lined bags or fiber drums. Keep dry, cool, and away from direct sunlight/heat sources. Avoid dust generation during loading. For bulk transport, confirm applicable waste/environmental regulations; Irgacure 184 is not typically regulated as dangerous goods, but verify per local SDS and shipping requirements. |
| Storage | Store Photoinitiator BASF Irgacure 184 in its original, tightly sealed container in a cool, dry, well-ventilated area away from heat, sparks, open flames, strong oxidizers, and direct sunlight or UV light. Keep container closed when not in use and protect from moisture to maintain stability and product performance. |
| Shelf Life | Shelf life is typically 12 months from manufacture if stored unopened, cool, dry, and protected from light. |
On flat-stock UV lines where 100% solids clear topcoats are applied by reverse roller coater to OEM kitchen cabinet fronts, Irgacure 184 is introduced as a pre-dissolved solution in 1,6-hexanediol diacrylate or dipropylene glycol diacrylate at a concentration of 2.0–4.0 wt% based on total formulation weight; high-build topcoats typically operate at 3.0 wt% because the Norrish Type I cleavage efficiency of the phenyl ketone under medium-pressure mercury emission at 254 nm and 313 nm must offset oxygen inhibition at the coating surface without generating excessive through-cure exotherm. The downstream process on industrial roller coaters uses anilox rolls delivering 10–40 g/m² wet film to pre-sanded, dust-extracted MDF or particleboard panels; curing follows under a gallium-doped medium-pressure Hg lamp array at 80–160 W/cm power and conveyor speeds of 5–15 m/min, corresponding to a UVA dose of 300–800 mJ/cm² and a peak irradiance above 0.6 W/cm². Compliance for wood surfaces intended for furniture and children’s products is governed by EN 71-3:2019+A1:2021 Table 2 for soluble elements, DIN 68861-1:2011 for chemical resistance classification of furniture surfaces, and ASTM D523-14 for specular gloss retained above 90 GU at 60°. Terminal finished product types include high-gloss clear topcoats on kitchen cabinet doors, UV-sealed parquet flooring, and clear protective layers on decorative melamine panels. The operational boundary is the solid-state melting point of Irgacure 184 near 47–50°C; batch tanks must maintain monomer temperature above 40°C during dissolution, because cold spots in recirculation lines produce recrystallization that can score gravure rollers and generate visible seeds. In formulations containing aromatic urethane acrylate oligomers, viscosity above 1,200 mPa·s at 25°C can be reduced without diluting the photoinitiator by pre-blending Irgacure 184 with propoxylated neopentyl glycol diacrylate at a 1:2 by-weight ratio before addition to the main batch.
In high-speed folding carton finishing lines, UV-curable overprint varnishes based on polyester acrylate and epoxy acrylate oligomers add Irgacure 184 at 3.0–5.0 wt% of total varnish to control surface gloss and block resistance; a typical in-line wet-offset OPV unit applies 3–8 g/m² through a three-roller chambered doctor blade system, and the varnish must achieve tack-free cure within 0.3–0.8 s under UV lamp heads positioned after the delivery section. At press speeds above 150 m/min, residual oxygen concentration in the varnish film remains high enough to inhibit the terminal radical population unless photoinitiator loading is increased toward 5.0 wt% and lamp power is raised to 160–200 W/cm. The production process requires anilox cell volumes of 12–25 cm³/m² to carry the low-viscosity varnish, and printed sheets are passed under iron-doped mercury vapor lamps emitting UVA, UVB, and UVC between 200–400 nm. Compliance for folding carton food packaging is assessed under Commission Regulation (EU) No 10/2011 Annex I and Annex III Table 2 migration testing with simulant E for dry foods or simulant D1 for fatty foods, and under FDA 21 CFR 175.300 for resinous and polymeric coatings; the EuPIA Suitability List for UV Printing Inks and Varnishes provides the industry migration screening framework. Terminal finished product types include high-gloss book covers, pharmaceutical cartons, cosmetic folding boxes, and label substrates. Irgacure 184 is not a polymeric or high-molecular-weight photoinitiator, so direct food-contact varnish on unprinted board without a functional barrier should not be specified; this limitation is particularly relevant for fatty food packaging where photoinitiator migration above the applicable EU 10/2011 Article 11 restriction would require a barrier layer or downstream offline lamination.
Applied as a clear or pigmented UV screen ink on flame-treated polycarbonate, PETG, or rigid PVC substrates, Irgacure 184 is incorporated at 2.0–5.0 wt% of ink weight, with transparent topcoats at 2.5 wt% and opaque whites containing 20–25 wt% titanium dioxide at 4.0–5.0 wt%; the higher loading in pigmented systems compensates for UV absorption by the pigment surface but cannot fully replace long-wavelength acylphosphine oxide initiators when pigment loading exceeds 25 wt%. The downstream screen-printing process uses a flatbed press with a 90–120 threads/cm mesh and a 75–90 Shore A squeegee, depositing a wet film thickness of 25–60 µm; after a 10–20 s infrared flash at 50–60°C to level the ink surface, the sheet proceeds through a UV tunnel with medium-pressure Hg lamps delivering 120–180 W/cm and a UVA dose of 400–900 mJ/cm². Compliance for rigid plastics used in toys, graphic panels, and electrical enclosures is anchored to EN 71-3:2019+A1:2021 Table 2 for soluble elements, REACH Annex XVII entries 51 and 52 for restricted phthalates in childcare articles, and RoHS Directive 2011/65/EU Annex II for printed circuit assemblies where the screen-printed layer overlays conductive traces. Terminal finished product types include membrane switch overlays, appliance control panels, nameplates, and in-mould decoration inserts. The operational limitation is Irgacure 184’s solid-state handling: screen inks with viscosity below 2,500 mPa·s at 25°C can retain undissolved particles if the powder is not pre-dissolved in tripropylene glycol diacrylate at 45°C for at least 30 min; undissolved particles pass the mesh and create pinholing after cure.
Under ISO 10993-5:2009 cytotoxicity documentation for UV-curable medical device assembly adhesives based on methacrylate-functionalized polyurethane or polyether oligomers, Irgacure 184 is used at 0.5–2.0 wt% of total adhesive weight; the lower end of the range is typical for low-durometer urethane acrylate joints, while 2.0 wt% is reserved for clear high-density bond lines under 500 µm where LED cure at 365 nm must penetrate without excessive surface skinning. The production process incorporates precision dispensing through a 25–30 gauge stainless steel needle at 0.1–0.5 MPa air pressure, followed by closed-loop UV curing with a 365 nm LED array delivering 2–10 J/cm² UVA to the bond line; clear polycarbonate or cycloolefin copolymer parts allow transmission above 80% at 365 nm. Compliance for biocompatibility is established by ISO 10993-5:2009 test method, USP <87> cytotoxicity classification, and ISO 13485:2016 process control in cleanroom assembly; adhesives intended for indirect food-contact devices additionally reference FDA 21 CFR 175.105 for structural adhesives used in contact with dry food. Terminal finished product types include needle hub bonding, catheter overmoulded ports, IV line connectors, and microfluidic chip lamination. The critical limitation is the optical clarity requirement: Irgacure 184 contributes low yellowing under standard cure but can form photodegradation byproducts when exposed to repeated ethylene oxide sterilization cycles, so ethylene oxide sterilization validation according to ISO 11135:2014 must be performed before specification on terminally sterilized devices.
At line speeds above 1,500 m/min on optical fiber draw towers where primary and secondary UV-curable acrylate coatings are applied wet-on-wet around a 125 µm glass core, Irgacure 184 is loaded at 1.0–2.5 wt% in the primary buffer and 1.5–3.0 wt% in the secondary protective layer, with offset against acylphosphine oxide photoinitiators in the secondary coating to maintain cure. The production process uses a dual coating die with a primary layer radial thickness of 25–35 µm and a secondary layer radial thickness of 25–40 µm, forming a nominal 245–250 µm final coated diameter; curing occurs in a nitrogen-purged quartz tube under medium-pressure mercury or microwave-excited UV lamps rated at 300–600 W/cm, with residual oxygen held below 200 ppm to prevent surface tack. Compliance is tested under IEC 60793-2-50:2018 for single-mode fibre geometric and optical parameters and Telcordia GR-20-CORE Issue 4 for coating strip force, microbending resistance, and environmental aging. Terminal finished product types include primary and secondary coatings for single-mode telecommunications fibre, bend-insensitive fibre, and multimode data-centre fibre. The inherent limitation of Irgacure 184 in this application is its solid-state precipitation at cold die temperatures; coating recirculation loops must be heated to 35–45°C, and any crystallized particles larger than 5 µm can cause coating concentricity failures because the die entrance gap is typically 150–250 µm.
For moisture-sensitive printed circuit board assemblies, UV-curable acrylate or acrylated polyurethane conformal coatings incorporate Irgacure 184 at 1.5–3.0 wt% based on total coating weight; the loading is kept below 3.0 wt% because higher concentrations increase surface crosslink density and inhibit the moisture-cure mechanism that must complete polymerization in shadow regions under surface-mount components and connectors. The downstream selective coating process uses an atomising spray valve with 0.2–0.5 mm nozzle diameter to deposit 50–200 µm wet film thickness on assembled boards; UV curing under a 365 nm LED line at 2–6 J/cm² fixes the coating surface within 1–3 s, and open sections are then transferred to a 25–30°C, 50–60% RH chamber for secondary moisture-cure completion over 24–72 h. Compliance to electrical and flammability requirements is verified under IPC-CC-830B for conformal coating qualification, UL 746E for electrical insulation in end-use equipment, ASTM D3359-17 cross-cut adhesion testing, and RoHS Directive 2011/65/EU Annex II for restricted substances. Terminal finished product types include conformal-coated engine control modules, power supply boards, sensor assemblies, and industrial automation controllers. The operational exposure risk is pre-drying: if board surface humidity exceeds 60% RH, moisture condensation at the coating interface produces blushing and adhesion failure; pre-baking at 60–80°C for 30–60 min is required before selective spray application.
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The photoinitiator BASF Irgacure 184 is 1-hydroxycyclohexyl phenyl ketone (CAS 947-19-3; molecular weight 204.26 g/mol), supplied as a white to off-white crystalline powder with a melting range of 45–49 °C. The substance initiates free-radical polymerisation in acrylate and methacrylate systems through Norrish Type I α-cleavage. UV absorption in the 240–330 nm region generates benzoyl and 1-hydroxycyclohexyl radicals. The product is used in clear coatings, overprint varnishes, adhesives, and UV-curable inks where low yellowing and solubility in reactive diluents are required. Unlike benzophenone-based initiating systems, Irgacure 184 does not require an amine co-initiator; the practical consequence is reduced amine odour and reduced amine-related surface defects in high-gloss topcoats.
Crystalline dissolution behaviour in TPGDA, HDDA, and TMPTA is a handling variable. Dissolution is typically carried out at 40–50 °C under low-shear stirring, and monomer concentrates containing 4–5 wt% Irgacure 184 are often stable at 25 °C if the storage temperature remains above 20 °C. Crystallisation may occur when such concentrates are held at 5–10 °C, producing filter-blocking particles during coating transfer. In high-viscosity urethane acrylate oligomers, pre-dissolving Irgacure 184 in a minor volume of warm monomer reduces the formation of undissolved particles; high-shear dispersion is not needed to achieve a clear solution once the crystalline powder is melted and mixed. For hot-melt acrylic systems, the melting range of 45–49 °C governs processing temperature. Hot-melt processors maintain jacketed vessels at 60–70 °C to ensure dissolution and avoid recrystallisation during coating. If the melt temperature drops below 45 °C, crystals can nucleate at transfer rollers and create surface defects. Production trials on slot-die coating lines have reported that maintaining die temperatures 5–10 °C above the melting point is sufficient to avoid blockages, but published data for this specific configuration is limited.
Published absorption data for Irgacure 184 in methanol show principal maxima near 244 nm and 280 nm, with declining absorbance at wavelengths longer than 330 nm. This wavelength range is effective for medium-pressure mercury lamps, but through-cure in heavily pigmented systems is constrained because titanium dioxide and carbon black attenuate UV-C and UV-B radiation. In a film containing Irgacure 184 alone, the upper layer polymerises rapidly and may absorb a large portion of the incident UV dose, reducing the photon flux available to the substrate side. The resulting hardness gradient is measurable by pendulum damping according to ISO 1522:2022 and by solvent resistance differences across the cross-section. For coatings with pigment volume concentrations above 15–20%, longer-wavelength photoinitiators such as TPO or BAPO are typically required to achieve cure through the film.
In oxygen-permeable coatings below 10 µm thickness, surface tack persists because atmospheric oxygen quenches the excited triplet state and scavenges free radicals. Formulators compensate by increasing Irgacure 184 concentration within its solubility limit, by using nitrogen inerting, or by adding a low-viscosity aliphatic urethane acrylate that promotes crosslink density rather than by adding amine synergists. Cure behaviour on open-face UV lines is evaluated with a combination of methyl ethyl ketone double rubs according to ASTM D5402-19, pendulum hardness according to ISO 1522:2022, and cross-cut adhesion according to ISO 2409:2020.
Benzophenone-based Type II systems require tertiary amine co-initiators to generate free radicals. Those systems exhibit deeper cure in thick sections because benzophenone has a longer triplet lifetime and can abstract hydrogen from amines, but they introduce amine migration, odour, and yellowing in clear topcoats. Irgacure 184 replaces the two-component initiation system with a single α-cleavage initiator, eliminating the amine reservoir and simplifying formulation. The trade-off is a narrower operational window for oxygen inhibition: benzophenone/amine systems may be more tolerant of oxygen because radical generation can continue through hydrogen abstraction, whereas Type I radical production from Irgacure 184 is more sensitive to anaerobic conditions near the surface. This difference is process-relevant on roll-to-roll coating lines where air entrainment varies with line speed.
Comparative data for four free-radical initiating packages in 100% reactive urethane acrylate clearcoats are summarised in the following table.
| Property | Irgacure 184 | Irgacure 1173 | Benzophenone/amine | TPO |
|---|---|---|---|---|
| Initiator class | Norrish Type I α-cleavage | Norrish Type I α-cleavage | Type II hydrogen abstraction | Norrish Type I α-cleavage |
| Primary methanol UV absorption maxima | 244 nm, 280 nm | 245 nm, 280 nm | 254 nm | 380–405 nm broad |
| Amine co-initiator requirement | None | None | Required | None |
| Yellowing tendency in clear acrylic | Low | Low | Moderate | Low to moderate |
| Suitability for LED cure at 395 nm | Limited without sensitiser | Limited without sensitiser | Limited | High |
| Typical loading in clear reactive diluent systems | 2–5 wt% | 2–5 wt% | 2–4 wt% plus amine | 0.5–3 wt% |
Direct replacement of benzophenone systems in existing formulations is not stoichiometric. Because Irgacure 184 generates radicals by photolytic cleavage, the concentration must be adjusted to compensate for the absence of amine hydrogen abstraction. Residual amines in poorly cleaned mixing vessels can still react with acidic degradation products; the resulting salt formation can affect conductivity and filter blockage. Equipment cleanout between benzophenone/amine and Irgacure 184 runs is therefore required to avoid contamination-related surface roughness.
On roll-to-roll UV flexographic coating lines, Irgacure 184 is not added as a free powder at the press; it is pre-dissolved in a monomer/oligomer premix. Dust generation during handling is reduced by closed transfer or local exhaust ventilation. The product should not be held above 60 °C in monomer solution for prolonged periods because thermally induced radical formation may shorten shelf life. Sealed containers stored at 30 °C or below and protected from moisture reduce caking. On printing lines, build-up on doctor blades or anilox rolls occurs when the formulation falls below the solubility limit due to overnight cooling to 15–18 °C; this is resolved by controlled pre-warming of the coating reservoir to 25–30 °C.
Volatility is a further difference between Irgacure 184 and 2-hydroxy-2-methylpropiophenone. The crystalline powder has a higher molecular mass and lower vapour pressure, which reduces evaporative loss during UV exposure on open conveyors. Thermogravimetric comparison under nitrogen can be performed according to ISO 11358-1:2022. In thin-film plastic coating, volatile photoinitiator loss can produce surface cure variability; Irgacure 184 is therefore preferred where low odour and reduced photoinitiator deposition on lamps are required.
The absorption spectrum of Irgacure 184 provides only limited absorbance at 395 nm; therefore, direct substitution of an LED array for a medium-pressure mercury lamp without reformulation can result in incomplete cure. Published data for the specific configuration of Irgacure 184 with 395 nm LED in thick clearcoats is limited, but the photochemistry of α-cleavage initiators indicates that longer-wavelength energy is not efficiently harvested unless the formulation includes a sensitiser or a long-wavelength photoinitiator. Where LED cure at 395 nm is required, Irgacure 184 is generally replaced by or blended with TPO or BAPO. Comparative assessments should record UV dose, peak irradiance, and cure response by pendulum hardness ISO 1522:2022 and MEK double rubs ASTM D5402-19 to prevent undetected under-cure in flexible packaging.
Post-cure photoyellowing is evaluated on the final lacquer rather than on the photoinitiator alone. Yellowing tendency in clearcoats is influenced by post-cure exposure and formulation aromatic content. Irgacure 184 is associated with lower initial yellowness than benzophenone/amine systems because the photoinitiator does not generate amine oxidation products. Assessment of colour is performed using CIE b* values according to ASTM E313-20 before and after UV weathering according to ISO 4892-3:2016. Published production data for exact b* targets in specific oligomer formulations are limited; therefore, confirmatory testing on the final lacquer composition is required before using Irgacure 184 where b* below 1.5 is a specification requirement.
Thick polyester castings above 2 mm exhibit a through-cure limitation for Irgacure 184 alone because UV attenuation in the bulk follows Lambert-Beer behaviour. In such cases, a long-wavelength initiator is added or the wavelength distribution of the lamp is shifted. Cure depth is quantified by hardness gradient across microtomed sections according to ISO 14577-1:2015 instrumented indentation rather than surface hardness only.
In low-residue UV flexographic packaging inks, Irgacure 184 is selected over benzophenone partly because of its lower migration potential associated with higher molecular mass and the absence of amine co-initiators. Migration testing is performed on printed or coated substrate using gas chromatography–mass spectrometry and extraction methods validated under EN 1186:2002. Compliance with EU Regulation 10/2011 and U.S. FDA 21 CFR 175.300 must be confirmed on the final printed article because migration depends on layer weight, degree of cure, substrate permeability, and storage time. Published data for this specific configuration is limited; therefore, a migration screen is required before use in indirect food-contact applications.
In white UV-curable screen inks containing titanium dioxide at 20–30 wt% pigment loading, Irgacure 184 is used in combination with TPO to obtain tack-free depth. The Irgacure 184 component contributes surface cure in short medium-pressure lamp passes, while TPO compensates for UV attenuation in the bulk. Formulators should measure through-cure by cross-sectional solvent resistance across the ink film and not solely by surface tack, because a hard surface can mask an under-cured lower layer. Cure is considered acceptable when the cross-section shows no delamination and no pigment transfer in a solvent rub test conducted in accordance with ASTM D5402-19.
