- ▸ Type II benzophenone-class photoinitiator with red-shifted absorption for high-throughput surface cure of UV coatings (Coatings & Construction)
- ▸ Used with amine synergists in UV/UV-LED inks (Industrial Manufacturing)
- ▸ Cures UV-curable plastics and adhesives (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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4-Benzoylbiphenyl is a red-shifted Type II benzophenone-type photoinitiator. The extra biphenyl ring extends conjugation, shifting absorption to longer UV than benzophenone — useful where deeper or slightly longer-wavelength surface cure is needed (with an amine synergist). Identity: CAS 2128-93-0.
What it is
4-Benzoylbiphenyl (CAS 2128-93-0) is a benzophenone analogue carrying a biphenyl group, a crystalline solid. The extended aromatic system red-shifts and strengthens its UV absorption relative to benzophenone.
How it cures
A Type II initiator that abstracts a hydrogen from an amine co-initiator under UV. Its longer-wavelength absorption helps it initiate where benzophenone is weak, and it is often used as a benzophenone upgrade in surface-cure packages with an amine synergist such as EDB or EHA.
Applications
Used in UV coatings and inks for surface cure where a stronger, longer-UV benzophenone is wanted, alongside a Type I initiator (TPO/184) for through cure. Compare benzophenone.
Forms, grades and handling
4-Benzoylbiphenyl is supplied as a crystalline solid. 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 4-Benzoylbiphenyl 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 II, benzophenone derivative) |
| Photoinitiator type | Type II (H-abstraction) |
| Absorption | Red-shifted UV (extended conjugation) |
| CAS Number | 2128-93-0 |
| Molecular Formula | C19H14O |
| Molecular Weight | 258.3 g/mol |
| Handling | Light-sensitive; refer to the current SDS |
Regulatory & registration requirements
- TSCA (US):
- REACH (EU):
- EC number: 218-345-2
Source: EPA TSCA Inventory (July 2025 release) · ECHA CHEM — retrieved 2026-07-12
Frequently Asked Questions
What is 4-benzoylbiphenyl used for?
4-Benzoylbiphenyl (PBZ, CAS 2128-93-0) is a Type II photoinitiator for UV surface cure with absorption red-shifted versus benzophenone; it is used with an amine synergist, usually with a Type I initiator for through cure.
How is bulk 4-benzoylbiphenyl supplied and quoted?
RawSource supplies 4-benzoylbiphenyl 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 4-Benzoylbiphenyl (PBZ)?
4-Benzoylbiphenyl (PBZ) (CAS 2128-93-0) 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 218-345-2).