2-Hydroxy-2-methylpropiophenone is a liquid α-hydroxy-ketone Type I photoinitiator exhibiting strong UV-A absorption (λmax ≈ 275 nm, shoulder 320–330 nm). Upon irradiation it undergoes α-cleavage to generate benzoyl and methyl radicals, initiating rapid, low-odour, low-yellowing polymerisation of acrylate, methacrylate and other vinyl monomers. The product is miscible with most UV-curable resins, plasticisers and solvents, practically insoluble in water (≈ 13 g L⁻¹ at 20 °C) and stable under neutral conditions. Commercial grade is supplied at ≥ 99 % purity and remains stable for ≥ 2 years when stored sealed at room temperature away from light .
Key Physicochemical Data:
Melting point: 4 °C
Boiling point: 102–103 °C / 4 mmHg
Density: 1.077 g cm⁻³ (25 °C)
Flash point: > 110 °C (closed cup)
Log P (octanol/water): 1.62 at 25 °C
Vapour pressure: 0.57 Pa at 20 °C
Typical Uses:
Universal Type I photoinitiator for UV-LED or mercury-lamp curing of clear and pigmented coatings, inks, adhesives, wood finishes, optical-fibre coatings and nail gels at 1–5 % w/w; features very low odour and yellowing .
Photosensitiser for thick-section (> 4 mm) and highly coloured (TiO₂, carbon-black) formulations with excellent through-cure .
Building block for synthesis of substituted propiophenones and UV-absorbing monomers .
Quality Specification (Commercial Grade):
Purity (GC): ≥ 99 %
Water content (KF): ≤ 0.3 %
Colour (Gardner): ≤ 2
Acid value: ≤ 1.0 mg KOH g⁻¹
Heavy metals: ≤ 20 ppm
Hazard Statement:
Harmful if swallowed (H302), causes skin irritation (H315) and serious eye irritation (H319) . Avoid inhalation of vapour; use gloves, goggles and adequate ventilation. Store in a cool, dry place away from oxidants and strong bases. SDS available on request.
