- ▸ Type I acylphosphine-oxide photoinitiator tuned for UV-LED (~380-420 nm) curing of clear and white-pigmented coatings and inks (Coatings & Construction)
- ▸ Long-wavelength absorption drives surface and through-cure of opaque/thick UV-LED layers in printing and electronics (Industrial Manufacturing)
- ▸ Low-yellowing fast cure of UV-curable adhesives, composites and 3D-print resins (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.
Request SDS →TPO Photoinitiator (CAS 75980-60-8) is diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, a low-odor pale-yellow solid. Identity: PubChem.
What it is
An acylphosphine oxide that cleaves under near-UV/violet light into two radicals, with strong absorption out to ~400 nm — which is exactly why it works under LED lamps where older initiators do not. Its radicals drive efficient deep/through cure, and the molecule photobleaches for low yellowing.
How it cures
TPO is a Type I (cleavage) acylphosphine-oxide photoinitiator. On absorbing near-UV/violet light it splits into radicals that drive fast, deep through-cure, and it photobleaches (loses its pale color as it reacts) for low final yellowing — making it a backbone initiator for both UV and LED systems.
Applications
TPO is used for through-cure in clear and pigmented UV/LED coatings, graphic-arts and 3D-printing inks, wood and plastic finishes, and adhesives. It is commonly blended with a surface-curing α-hydroxyketone such as 184 or 1173 for balanced surface-plus-depth cure, and with BAPO for heavily pigmented films.
Forms, grades and handling
TPO is supplied as a fine pale-yellow powder (and in liquid TPO-L form). Photoinitiators are light-sensitive — store cool and dark. Many are fine powders or liquids that require dust/handling controls 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 TPO Photoinitiator 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 or blend. 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 | TPO Photoinitiator — Photoinitiator (Type I, acylphosphine oxide) |
| Type | Type I (cleavage) |
| Absorption | Near-UV / violet — LED-suitable (to ~400 nm) |
| Key strength | Deep/through cure; photobleaching/low yellowing |
| Appearance | Pale-yellow powder |
| CAS Number | 75980-60-8 |
| Molecular Formula | C22H21O2P |
| Handling | Light-sensitive; refer to the current SDS |
Regulatory & registration requirements
- TSCA (US):
- REACH (EU):
- EC number: 278-355-8
TSCA Inventory flag PMN: a commenced PMN (premanufacture notice) substance (EPA flag legend).
Source: EPA TSCA Inventory (July 2025 release) · ECHA CHEM — retrieved 2026-07-12
Regulatory restriction status
TPO Photoinitiator (Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide) (CAS 75980-60-8) appears on the regulatory list(s) below. This is public regulatory information about the substance — not a statement about any specific supplier’s material, and not a safety claim. Confirm the current status for your jurisdiction and intended use.
- REACH SVHC Candidate List (EU): listed 14 Jun 2023 on the basis of toxic for reproduction (Art. 57(c)). SVHC status triggers EU supplier-communication and notification duties above 0.1% w/w; it is not, by itself, a ban on sale.
Sources: ECHA Candidate List / Annex XIV / Annex XVII (echa.europa.eu); U.S. EPA TSCA; UN Stockholm Convention / EU POPs Regulation; California OEHHA Proposition 65 list. Retrieved 2026-07-13.
Frequently Asked Questions
What is TPO photoinitiator used for?
TPO (CAS 75980-60-8) is a Type I acylphosphine-oxide photoinitiator used for deep/through cure of UV and LED coatings, inks, 3D-printing resins and adhesives, with low yellowing; it is often blended with a hydroxyketone for surface cure.
Is TPO suitable for LED curing?
Yes — TPO absorbs into the violet/near-400 nm region, so it responds to LED lamps, which is a major reason it is used in LED-cure coatings and inks.
What is the difference between TPO and TPO-L?
Both are acylphosphine-oxide Type I initiators; TPO is a solid powder and TPO-L is the liquid ethyl ester analogue, chosen for easier handling and clear liquid formulations.
Why does TPO give low yellowing?
It photobleaches — the chromophore is consumed as it reacts — so the cured film ends up with little residual color, unlike some initiators that yellow.
How is bulk TPO supplied and quoted?
RawSource supplies TPO as a powder (and TPO-L liquid) in bulk with CoA, TDS and SDS. Pricing is quote-based on grade and volume; submit an RFQ with your target quantity.
What is the REACH and TSCA regulatory status of TPO Photoinitiator (Diphenyl(2,4,6-trimethylbenzoyl)phosphine Oxide)?
TPO Photoinitiator (Diphenyl(2,4,6-trimethylbenzoyl)phosphine Oxide) (CAS 75980-60-8) is subject to U.S. TSCA Inventory requirements; supplying it into the EU requires valid REACH registration ((EC) No 1907/2006). RawSource cannot verify a third-party supplier's registrations — buyers should require documented TSCA and REACH compliance for their jurisdiction and volume (EC 278-355-8).