TPO-L is a liquid phosphine-oxide photoinitiator combining a 2,4,6-trimethylbenzoyl group with an ethyl phenylphosphinate moiety. It exhibits strong UV-A absorption (λmax 299 & 366 nm) and undergoes efficient α-cleavage to produce both benzoyl and phosphonyl radicals, enabling rapid, low-odour, low-yellowing cure of acrylate, methacrylate and vinyl systems. The product is miscible with most oligomers and monomers, practically insoluble in water (≈ 35 mg L⁻¹ at 25 °C) and stable under neutral conditions. Commercial grade is supplied at ≥ 98 % purity and remains stable for ≥ 2 years when stored at 2–8 °C under nitrogen .
Key Physicochemical Data:
Density: 1.14 g cm⁻³ (20 °C)
Boiling point: 456 ± 55 °C (predicted)
Flash point: > 150 °C (closed cup, predicted)
Log P (octanol/water): 2.91 (25 °C)
Vapour pressure: < 0.1 Pa at 20 °C
Typical Uses:
Universal Type I photoinitiator for UV-LED or mercury-lamp curing of screen, flexo and offset inks, over-print varnishes, wood coatings and white/pigmented systems at 0.3–5 % w/w .
Photosensitiser for thick-section (> 4 mm) and highly coloured formulations with low shrinkage and excellent surface-through-cure .
Synergist with benzophenone, 184 or 1173 for enhanced surface cure and reduced odour .
Quality Specification (Commercial Grade):
Purity (HPLC): ≥ 98 %
Water content (KF): ≤ 0.3 %
Acid value: ≤ 1.0 mg KOH g⁻¹
Clarity: clear
Heavy metals: ≤ 20 ppm
Hazard Statement:
Harmful if swallowed (H302), causes skin irritation (H315), serious eye irritation (H319), may cause respiratory irritation (H335) . Avoid breathing mist/vapours; use gloves, goggles and local exhaust. Store under inert gas at 2–8 °C away from light and moisture. SDS available on request.
