- ▸ Type I bis-acylphosphine-oxide (BAPO) photoinitiator giving deep through-cure of pigmented and white UV coatings (Coatings & Construction)
- ▸ Long-wavelength absorption suits UV-LED and thick-film inks/electronics where surface initiators fail to cure depth (Industrial Manufacturing)
- ▸ Cures thick UV/EB adhesives, gel coats and composite layers with low yellowing (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 →BAPO (CAS 162881-26-7) is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, a yellow powder. Identity: PubChem.
What it is
A bis-acylphosphine oxide that generates four radicals per molecule on photolysis, giving very high through-cure efficiency even in thick and pigmented films, with strong long-UV/violet absorption for LED cure and good photobleaching.
How it cures
BAPO is a bis-acylphosphine-oxide Type I photoinitiator (the bis version of TPO, also known as 819). With two cleavable acyl groups it is exceptionally efficient at deep and pigmented through-cure and absorbs well into the violet/near-visible for LED systems, while photobleaching for low final color.
Applications
BAPO is used where deep or pigmented through-cure is critical: white and pigmented UV/LED coatings and inks, thick castings, composites, electronics and 3D printing. It is often paired with a surface-curing hydroxyketone (184/1173) and complements TPO.
Forms, grades and handling
BAPO is supplied as a yellow powder. 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 BAPO 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 | BAPO Photoinitiator — Photoinitiator (Type I, bis-acylphosphine oxide) |
| Type | Type I (cleavage), bis-acylphosphine oxide |
| Absorption | Long-UV / violet — LED-suitable |
| Key strength | Maximum deep/pigmented through-cure; photobleaching |
| Appearance | Yellow powder |
| CAS Number | 162881-26-7 |
| Molecular Formula | C26H27O3P |
| Handling | Light-sensitive; refer to the current SDS |
Regulatory & registration requirements
- TSCA (US):
- REACH (EU):
- EC number: 423-340-5
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
Frequently Asked Questions
What is BAPO photoinitiator used for?
BAPO (CAS 162881-26-7, also called 819) is a bis-acylphosphine-oxide Type I initiator for deep and pigmented through-cure of UV/LED coatings, inks, thick castings, composites and 3D-printing resins.
How is BAPO different from TPO?
Both are acylphosphine-oxide Type I initiators; BAPO is the bis (two-acyl) version, giving higher through-cure efficiency in thick and pigmented films, while TPO is the mono version. They are often used together with a surface-cure hydroxyketone.
Is BAPO good for LED?
Yes — it absorbs into the violet/near-visible, so it responds to LED lamps and is widely used in LED-cure pigmented systems.
What is the CAS of BAPO?
It is CAS 162881-26-7 (PubChem CID 164512), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide. The CoA documents grade.
How is bulk BAPO supplied and quoted?
RawSource supplies it as a powder in bulk with CoA, TDS and SDS. Pricing is quote-based on grade and volume; submit an RFQ.
What is the REACH and TSCA regulatory status of BAPO Photoinitiator (Phenylbis(2,4,6-trimethylbenzoyl)phosphine Oxide)?
BAPO Photoinitiator (Phenylbis(2,4,6-trimethylbenzoyl)phosphine Oxide) (CAS 162881-26-7) 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 423-340-5).