- ▸ Liquid Type I acylphosphinate photoinitiator for low-yellowing, easy-handling cure of clear and white UV coatings (Coatings & Construction)
- ▸ Long-wavelength liquid initiator ideal for UV-LED inks and digital printing (Industrial Manufacturing)
- ▸ Cures UV-curable adhesives, composites and resins with good depth cure (Plastics & Polymers)
A grade-specific Safety Data Sheet (SDS) — with the complete hazard classification, handling precautions, and transport information — is supplied with every shipment and available on request. Confirm all safety and regulatory details against the SDS for your specific grade.
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TPO-L is the liquid monoacylphosphine-oxide Type I photoinitiator — the liquid ethyl-ester analogue of TPO. It cleaves under near-UV/violet light for fast deep/through cure, photobleaches for low yellowing, and as a liquid is easy to meter and disperse, including in LED systems. Identity: CAS 84434-11-7.
What it is
Ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate (CAS 84434-11-7) is the liquid acylphosphine-oxide counterpart to solid TPO. Its liquid form simplifies handling and is preferred in clear liquid formulations.
How it cures
A Type I acylphosphine oxide: it cleaves under near-UV/violet light into radicals that drive efficient deep/through cure, with strong absorption out to ~400 nm for LED lamps, and it photobleaches for low final color — no amine needed.
Applications
Used for through-cure of UV/LED coatings, inks, 3D-printing resins, clearcoats and adhesives, especially where a liquid is wanted; commonly blended with a surface-curing hydroxyketone (184/1173). Solid alternatives: TPO and BAPO.
Forms, grades and handling
TPO-L is supplied as a clear-to-pale liquid. Photoinitiators are light-sensitive — store cool, dry and dark, away from light and ignition sources. Handle per the current Safety Data Sheet (SDS); each lot ships with a Certificate of Analysis (CoA) and Technical Data Sheet (TDS).
Bulk supply and RFQ
RawSource sources Ethyl direct from producers in bulk, with CoA, TDS and SDS per lot. Tell us your lamp (mercury or LED wavelength), system (clear or pigmented) and cure target, and we will quote the right grade. Compare the full range and selection logic in the photoinitiators guide.
Typical Properties
Typical reference values, not a specification; the Certificate of Analysis (CoA) for the lot governs.
| Property | Typical Value |
|---|---|
| Chemical / type | Photoinitiator (Type I, liquid acylphosphine oxide) |
| Photoinitiator type | Type I (cleavage), monoacylphosphine oxide (liquid) |
| Absorption | Near-UV / violet — LED-suitable (to ~400 nm) |
| CAS Number | 84434-11-7 |
| Molecular Formula | C18H21O3P |
| Molecular Weight | 316.3 g/mol |
| Handling | Light-sensitive; refer to the current SDS |
Regulatory & registration requirements
- TSCA (US): Not found on the public (non-confidential) TSCA Inventory
- REACH (EU):
- EC number: 282-810-6
Source: EPA TSCA Inventory (July 2025 release) · ECHA CHEM — retrieved 2026-07-12
Frequently Asked Questions
What is TPO-L used for?
TPO-L (CAS 84434-11-7) is a liquid Type I acylphosphine-oxide photoinitiator for deep/through cure of UV and LED coatings, inks, 3D-printing resins and adhesives, with low yellowing; it is the liquid analogue of TPO and is blended with a hydroxyketone for surface cure.
How is TPO-L different from TPO?
Both are acylphosphine-oxide Type I initiators; TPO-L is the liquid ethyl ester (easy to meter, clear liquid systems) and TPO is the solid powder. They cure similarly; choose by physical form.
Is TPO-L suitable for LED curing?
Yes — it absorbs into the violet/near-400 nm region, so it responds to LED lamps and is widely used in LED-cure systems.
How is bulk TPO-L supplied and quoted?
RawSource supplies TPO-L in bulk with CoA, TDS and SDS per lot. Pricing is quote-based on grade and volume; submit an RFQ with your target quantity.
What is the REACH and TSCA regulatory status of Ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate?
Ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate (CAS 84434-11-7) is recorded as REACH-registered in ECHA's public CHEM database (EC 282-810-6); it was not found on EPA's public (non-confidential) TSCA Inventory file.