TPO (CAS 75980-60-8)
| CAS No. | 75980-60-8 |
|---|---|
| Alias | Diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide |
| Category | Photoinitiators |
| Purity | ≥98.00% (HPLC) |
| Packaging | 20kg/carton |
TPO is a general-purpose free radical photoinitiator with long absorption wavelength, excellent deep curing performance and photo-bleaching property. It is particularly suitable for LED-curable coatings and inks. When used together with 184, it provides more balanced overall performance.
Equivalent grades. The same substance is sold by other manufacturers as Omnirad TPO, Speedcure TPO, Genocure TPO, Lucirin TPO. It is the same CAS number (75980-60-8) and the same chemistry, so a formulation written around one of those grades transfers directly.
Introduction
TPO is the photoinitiator most formulators reach for when the lamp is an LED. Its absorption reaches 370 nm, far enough into the visible range to catch the 365 and 395 nm output that LED arrays actually deliver. Mercury lamps cure it too; LEDs are where it earns its price.
The other reason people specify TPO is depth. Where 184 and 1173 concentrate their work near the surface, TPO keeps absorbing as it photobleaches, so through-cure in a pigmented or thick film is markedly better. That bleaching matters twice: the yellow cast a phosphine oxide normally leaves behind fades as curing proceeds, which is why TPO appears in clearcoats that cannot tolerate a colour shift.
Physical & Chemical Properties
Light yellow powder. Molecular formula C22H21O2P, molecular weight 348.38, purity ≥98.00% by HPLC, melting range 85.0–95.0 °C, loss on drying ≤0.5%. Absorption maxima at 273 nm and 370 nm.
Applications
Typical loadings are 1–3% by weight in coatings and 5–10% in inks. Those figures come from our technical data and from what customers report; your mill base and line speed will move them. TPO is rarely used alone. Blending it with 184 flattens the cure profile across the film, and most of the LED formulations we ship go out as a two-component package for that reason. TPO is a solid and does not dissolve instantly, so a warm-up or premix step helps. If your process cannot tolerate one, TPO-L is the liquid version of the same chemistry.
Regulatory status (EU)
TPO is on the REACH Candidate List as an SVHC (added June 2023) and carries a harmonised Repr. 1B classification applying from 1 September 2025. Commission Regulation (EU) 2025/1731 brought it into Annex XVII by way of Appendix 6 to Entry 30, which restricts supply to the general public; industrial formulation is not general public supply. In Switzerland it remains positively listed in Annex 10 of SR 817.023.21 at 0.05 mg/kg. It is not listed in category V of the German Anlage 14, and because the German framework excludes CMR substances from the non-listed route, it is effectively unusable there rather than formally prohibited. EuPIA removed it from its suitability list in January 2026, and ECHA recommended it for the Authorisation List in November 2025. That recommendation is not yet law. Anyone specifying TPO for a European line should be tracking it.
Handling & Storage
Keep in a tightly closed container in a cool, dry, dark, ventilated area. Shelf life one year from production in the sealed original container. Refer to the SDS before handling.
Packaging
20 kg cartons as standard, custom packaging on request. COA with every batch, SDS available in English.
Applications & Industries
Coatings & Paints
Metal driers (cobalt, manganese, zirconium octoate, naphthenates) and photoinitiators for coatings, paints, varnishes and industrial finishes — with COA & MSDS per batch.
UV Curing & Printing Inks
Free radical photoinitiators for UV-curable inks, coatings, adhesives and 3D printing — 1173, 184, 369, 907, ITX, DETX, TPO/TPO-L and liquid blends, QC-tested per batch.
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Frequently Asked Questions
What is your minimum order quantity (MOQ)?
MOQ depends on the product and specification. For most chemicals we can supply from 1 kg sample orders up to full container loads (FCL). Contact us with the product name and CAS number for a specific MOQ quotation.
Can you provide samples before I place a bulk order?
Yes. Samples are available for most products — typically 100g to 1kg. Sample fees may apply for expensive products and are usually deducted from your first bulk order. We recommend independent testing of samples before committing to bulk.
What documents do you provide with each shipment?
Every shipment includes a batch-specific Certificate of Analysis (COA), MSDS/SDS, commercial invoice, packing list and bill of lading. Certificates of origin, REACH/SVHC declarations and third-party inspection reports are available on request.
What is your typical lead time?
Production usually takes 10–20 days depending on the product and quantity. Sea freight to most destinations takes 15–30 days; air freight 5–10 days for samples and small orders. Our five warehouses in China allow fast dispatch of stocked items.
What payment terms do you accept?
We commonly accept 30% deposit + 70% against copy of bill of lading, T/T bank transfer, and Letters of Credit (L/C) for larger orders. Payment terms are confirmed in writing before production starts.
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We are an integrated supplier with three in-house manufacturing plants, supported by five warehouses across China. This gives us direct control over production quality while maintaining a broad product range.