A high-activity cationic photoinitiator supplied either as neat crystals or as a 50 % solution in propylene carbonate. The triarylsulfonium core absorbs strongly at 250–330 nm and photolyzes to generate super-acid (HPF₆), initiating rapid cationic polymerisation of epoxides, vinyl ethers, oxetanes and glycidyl systems. It offers low odour, low yellowing, excellent through-cure (> 4 mm) and good thermal latency. Commercial material is stable for ≥ 2 years when stored sealed at 2–8 °C away from moisture and light .
Key Physicochemical Data (2025 update):
Melting point: 118–119 °C
Density: 1.40 g cm⁻³ (20 °C)
Flash point: 145 °C (closed cup)
Vapour pressure: 0.002 Pa at 25 °C
Water solubility: 74 mg L⁻¹ at 20 °C
Log P (octanol/water): –0.43 at 20 °C
GHS Classification (2025):
Skin Sens. 1A: H317 – May cause an allergic skin reaction
Aquatic Chronic 2: H411 – Toxic to aquatic life with long-lasting effects
Acute Tox. 4: H302 – Harmful if swallowed; H332 – Harmful if inhaled
Hazard Class 8 (corrosive to skin/eye) with Packing Group III; UN 1549 for transport .
Typical Uses:
Universal cationic photoinitiator for UV-LED or mercury-lamp curing of clear and pigmented epoxies, vinyl ethers, oxetanes and hybrid UV-cationic systems at 0.5–4 % w/w.
Deep-section (> 3 mm) and high-speed printing inks, solder-mask, optical-fibre coatings, 3-D stereolithography resins.
Synergist with free-radical photoinitiators for hybrid cure or dual-cure formulations.
Quality Specification (Commercial Grade):
Purity (HPLC): ≥ 98 %
Water content (KF): ≤ 0.3 %
Chloride: ≤ 100 ppm
Heavy metals: ≤ 20 ppm
Transmittance (500 nm, 10 % in PC): ≥ 85 %
Hazard Statement:
May cause allergic skin reaction (H317); harmful if swallowed or inhaled (H302 + H332); toxic to aquatic life with long-lasting effects (H411). Avoid breathing dust/vapour; use gloves, goggles and local exhaust. Store under inert gas at 2–8 °C away from light and moisture. SDS available on request.
