- ▸ Highly reactive Type I benzil-ketal photoinitiator for fast cure of clear UV coatings and varnishes (Coatings & Construction)
- ▸ Used in UV inks and high-speed line curing (Industrial Manufacturing)
- ▸ Cures clear UV-curable adhesives, composites and unsaturated-polyester systems (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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Benzil dimethyl ketal (BDK, also called 651) is a highly efficient Type I cleavage photoinitiator. It cleaves under UV into radicals for fast, deep cure of clear systems — a classic high-activity initiator for clear coatings and adhesives, though it can contribute more yellowing than hydroxyketones. Identity: CAS 24650-42-8.
What it is
Benzil dimethyl ketal (CAS 24650-42-8, 2,2-dimethoxy-2-phenylacetophenone) is a white crystalline solid. It is one of the most efficient Type I initiators and a long-standing standard for clear UV systems.
How it cures
A Type I initiator: UV alpha-cleavage produces benzoyl and dimethoxybenzyl radicals (the latter fragments further), giving very efficient radical generation and fast deep cure — no amine needed. Its benzaldehyde-type byproducts can cause some yellowing and odor, managed by formulation.
Applications
Used for fast deep and surface cure of clear UV coatings, adhesives, castings and electronics. For lower yellowing compare 184/1173; pair with TPO/BAPO for thick or pigmented work.
Forms, grades and handling
BDK is supplied as a white crystalline powder. 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 Benzil Dimethyl Ketal 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, benzil ketal) |
| Photoinitiator type | Type I (cleavage), benzil ketal |
| Absorption | UV (mercury-lamp range) |
| CAS Number | 24650-42-8 |
| Molecular Formula | C16H16O3 |
| Molecular Weight | 256.30 g/mol |
| Handling | Light-sensitive; refer to the current SDS |
Regulatory & registration requirements
- TSCA (US):
- REACH (EU):
- EC number: 246-386-6
Source: EPA TSCA Inventory (July 2025 release) · ECHA CHEM — retrieved 2026-07-12
Frequently Asked Questions
What is benzil dimethyl ketal (BDK/651) used for?
BDK (CAS 24650-42-8) is a highly efficient Type I cleavage photoinitiator for fast deep/surface cure of clear UV coatings, adhesives and castings; it needs no amine synergist but can contribute some yellowing and odor.
Does BDK yellow?
It is high-activity but its cleavage byproducts can cause more yellowing/odor than the hydroxyketones (184/1173), so it is used where high cure speed outweighs color, or balanced in formulation.
How is bulk benzil dimethyl ketal supplied and quoted?
RawSource supplies benzil dimethyl ketal 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 Benzil dimethyl ketal (2,2-dimethoxy-2-phenylacetophenone)?
Benzil dimethyl ketal (2,2-dimethoxy-2-phenylacetophenone) (CAS 24650-42-8) 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 246-386-6).