Photoinitiator TPO-L is a liquid Type I phosphine oxide photoinitiator used in free-radical UV curing. Its CAS number is 84434-11-7. It absorbs UV or LED light, forms free radicals, and helps acrylate coatings, inks, adhesives, varnishes, and photopolymer resins cure into a solid film.
Industrial buyers choose TPO-L when they need:
- Liquid dosing instead of powder feeding
- Easier blending in acrylate systems
- Low-yellowing UV curing performance
- Better process control in ink, coating, adhesive, and resin production
- A practical comparison option against TPO, 819, 1173, and 184
The main caution is clear: TPO-L is not a blind 1:1 replacement for every TPO formula. Before bulk purchase, test dosage, lamp wavelength, pigment load, film thickness, cure depth, yellowing, odor, and final mechanical properties.
If you are sourcing from China, start with UVIXE’s TPO-L photoinitiator supplier page and request COA, SDS, TDS, sample quantity, lead time, and FOB quotation before ordering drums.
What is Photoinitiator TPO-L?
Photoinitiator TPO-L is a liquid photoinitiator used to start polymerization in UV-curable formulas. In simple terms, it turns light energy into a curing reaction. When UV or LED light hits TPO-L, the molecule creates free radicals. These radicals help liquid acrylate materials become a cured coating, ink layer, adhesive bond, or resin part.
The chemical name is commonly listed as ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate. The ECHA chemical database identifies it with CAS number 84434-11-7 and EC number 282-810-6. PubChem also lists its molecular formula as C18H21O3P.
I explain TPO-L to buyers this way: it is not only a chemical additive. It is a production-speed, curing-risk, and documentation decision. A good TPO-L match can improve process flow. A poor match can cause tacky film, weak bottom cure, yellowing, odor complaints, rejected batches, or delayed customer approval.
TPO-L Identity Table for Industrial Buyers
| Item | TPO-L Information | Why It Matters for Buyers |
|---|---|---|
| Product name | Photoinitiator TPO-L | Common sourcing name in UV curing |
| CAS number | 84434-11-7 | Confirms identity on COA, SDS, TDS, and customs files |
| Chemical name | Ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate | Helps R&D verify the material |
| Type | Type I photoinitiator | Generates radicals after light exposure |
| Chemical family | Phosphine oxide photoinitiator | Often used for depth cure and low-yellowing targets |
| Physical form | Liquid | Easier dosing and blending than powder initiators |
| Main curing system | Free-radical UV curing | Common in acrylate coatings, inks, adhesives, and resins |
| Typical buyers | UV coating, UV ink, UV adhesive, SLA/DLP resin factories | Matches industrial procurement needs |
If you are still building the basic photoinitiator selection map, read UVIXE’s guide on what does a photoinitiator do before choosing TPO-L.
How Does TPO-L Work in UV Curing?
TPO-L works through a free-radical curing mechanism. It absorbs UV or LED light, splits into active radicals, and starts polymerization of acrylates or other unsaturated materials. The ScienceDirect photoinitiator overview explains photoinitiators as compounds that form reactive species after light absorption.
That definition is useful, but factory curing depends on real line conditions. TPO-L does not cure by CAS number. It cures only when the formula, lamp, coating thickness, and production speed match.
Important curing variables include:
- Lamp wavelength
- UV energy dose
- Conveyor or printing speed
- Film thickness
- Pigment type and loading
- Resin and monomer structure
- Oxygen inhibition at the surface
- Photoinitiator dosage and blend design
My First Question Before Recommending TPO-L
When a buyer asks me for TPO-L price, I usually ask this first:
What lamp are you using: mercury, LED 365 nm, LED 385 nm, LED 395 nm, or LED 405 nm?
Without this answer, a supplier can quote the correct material but still fail your curing target. Arkema notes that UV LED curing uses narrower lamp output, often around the 365–405 nm range, so photoinitiator selection must match the light source through its UV LED photoinitiator guidance.
Key Technical Properties of Photoinitiator TPO-L
TPO-L is widely selected because it is liquid, easy to blend, and useful in many low-yellowing UV systems. Arkema’s SpeedCure TPO-L technical profile describes TPO-L as a liquid Norrish Type I photoinitiator from the phosphine oxide family, with absorption maxima at 274, 290, and 370 nm. Arkema also gives a use level of 0.5–5 wt% in UV and LED curable formulations.
IGM Resins describes Omnirad TPO-L as a liquid Type I photoinitiator used to initiate radical polymerization of acrylates, unsaturated polyesters, and reactive diluent systems after UV exposure.
These references help define the material. They do not replace lab trials.
Technical Property Matrix
| Property | Practical Meaning | Buyer Interpretation |
|---|---|---|
| Liquid form | Easier to dose, pump, and blend | Useful for coating, ink, adhesive, and resin production lines |
| Type I mechanism | Forms radicals directly after light exposure | Supports free-radical acrylate curing |
| Phosphine oxide structure | Often supports depth cure | Important for thicker films and pigmented formulas |
| Absorption profile | Includes long-wave UV response | Helps LED UV and deep-cure trials |
| Low-yellowing tendency | Less visible color shift in many systems | Useful for clear coats, white inks, and light-color resins |
| Typical use level | Broadly referenced at 0.5–5 wt% | Final dosage must be tested |
| Documentation need | COA, SDS, TDS, label, batch traceability | Required for procurement, audits, and export |
Where is Photoinitiator TPO-L Used?
TPO-L is used in industrial UV curing systems where liquid handling, low yellowing, and curing depth matter. It can be used in UV coatings, UV inks, UV adhesives, overprint varnishes, and photopolymer resins.
I do not recommend treating all applications the same. A UV wood coating line and a DLP resin company may both ask for TPO-L, but their failure points are different.
Application Matrix for TPO-L
| Application | Why Buyers Test TPO-L | Main Risk to Check |
|---|---|---|
| UV wood coating | Low yellowing and good curing in clear or light-color coatings | Surface tack, hardness, and gloss |
| UV plastic coating | Fast curing on industrial parts | Adhesion and substrate heat sensitivity |
| UV metal coating | Topcoat and protective coating trials | Cure depth and corrosion test performance |
| UV screen ink | Liquid blending and strong cure demand | Pigment blocking and odor |
| UV flexo ink | Fast printing and lower viscosity systems | Press speed and cure completeness |
| UV offset ink | Low yellowing and cure strength | Pigment load and ink-water balance |
| UV adhesive | Acrylate adhesive curing | Bond-line thickness and substrate transparency |
| SLA/DLP resin | Photopolymer resin curing trials | Cure depth, resolution, color, and brittleness |
| Overprint varnish | Clear protective layer curing | Gloss, blocking resistance, and yellowing |
For application-specific sourcing, UVIXE supports industrial buyers across photoinitiator supplier options including TPO-L, TPO, 819, 1173, 184, ITX, DETX, 907, and 369.
Why Do UV Factories Choose Liquid TPO-L?
Factories often choose TPO-L because it is liquid. That may sound simple, but in daily production it can change the workflow.
Powder photoinitiators may create issues in weighing, dust control, dissolution, and batch consistency. Liquid TPO-L is easier to pump, dose, pre-mix, and blend into many acrylate systems. This matters for ink, coating, adhesive, and resin factories that run multiple formulas in one shift.
I have seen buyers lose money not because they paid slightly more per kg. They lost money because the photoinitiator did not dissolve well, did not cure deeply enough, or arrived without documents their customer needed.
TPO-L buyer rule: Do not compare TPO-L only by price per kg. Compare it by cure speed, dosage, yellowing result, batch consistency, handling cost, and document readiness.
Main Reasons Buyers Choose TPO-L
- Liquid form supports easier production dosing
- Low-yellowing behavior helps clear and light-color systems
- Phosphine oxide chemistry supports deeper curing in many UV systems
- It can be tested in LED UV curing lines
- It works well in photoinitiator blend strategies
- It reduces some powder-handling issues in production
TPO-L vs TPO: What is the Real Difference?
TPO-L and TPO are both phosphine oxide photoinitiators, but they are not the same product. TPO is usually supplied as a powder. TPO-L is liquid. This changes handling, blending, storage, dosing, and production workflow.
Arkema’s SpeedCure TPO technical profile lists TPO as a Norrish Type I photoinitiator from the phosphine oxide family with CAS 75980-60-8. TPO-L uses CAS 84434-11-7. Same family does not mean same formulation behavior.
For a deeper internal comparison, read UVIXE’s TPO vs TPO-L photoinitiator comparison.
TPO-L vs TPO Decision Table
| Buyer Situation | Better Starting Point | Why |
|---|---|---|
| Automated liquid dosing line | TPO-L | Easier pumping and blending |
| Existing powder TPO formula already approved | TPO | Do not change a proven system without need |
| Low-yellowing clear coating trial | TPO-L or blend | Good starting point for color-sensitive systems |
| Thick white UV ink | TPO, TPO-L blend, or 819 support | TiO₂ blocks UV light, so through-cure must be tested |
| LED 395 nm curing line | TPO-L trial with validation | Match wavelength, dosage, and film thickness |
| EU-facing reformulation project | TPO-L trial with document review | Check REACH, CLP, SDS, and customer acceptance |
| Distributor stocking one flexible liquid initiator | TPO-L | Easier to sell into several liquid UV systems |
| High-speed industrial ink line | Lab comparison required | Press speed and pigment load decide performance |
TPO-L replacement rule: TPO-L can sometimes replace TPO, but replacement must be validated by lamp wavelength, cure depth, film thickness, pigment load, surface cure, and final mechanical testing.
Should You Choose TPO-L, TPO, 819, 1173, or 184?
Many buyers search for TPO-L but actually need a broader photoinitiator decision. TPO-L is not always the best answer. It depends on application, color, cure depth, lamp, and compliance requirements.
Photoinitiator Selection Logic
| Photoinitiator | Common Buyer Reason | Main Caution |
|---|---|---|
| TPO-L | Liquid handling, low yellowing, LED UV trials | Not always equal to TPO in cure speed |
| TPO | Strong phosphine oxide initiator for many UV systems | Powder handling and market-specific regulatory concerns |
| 819 / BAPO | Deep cure and pigmented systems | Yellowing and dosage balance need testing |
| 1173 | Clear coatings and surface cure support | May not solve deep cure alone |
| 184 | General UV curing and coating use | Limited in very thick or heavily pigmented systems |
If you are comparing alternatives, review UVIXE’s TPO photoinitiator for UV curing before switching from TPO to TPO-L.
Recommended Dosage of TPO-L by Application
A broad industrial reference range for TPO-L is 0.5–5 wt%, but no serious factory should copy that number without testing. Dosage depends on resin type, pigment, lamp energy, cure speed, film thickness, and final performance target.
I prefer ladder testing. Do not test only one percentage. Test low, medium, and high loading under your actual lamp and line speed. Then measure surface cure, through-cure, yellowing, odor, adhesion, and storage stability.
TPO-L Dosage Starting Matrix
| Application | Starting Trial Range | Lamp / Formula Note | What to Check First |
|---|---|---|---|
| Clear UV coating | 0.5–2.0% | Mercury or LED after validation | Gloss, hardness, yellowing, surface tack |
| Pigmented UV coating | 1.0–4.0% | Pigment blocks light penetration | Through-cure, adhesion, hiding power |
| White UV ink | 2.0–5.0% | TiO₂ may require initiator blend | Bottom cure, odor, ink transfer |
| Clear overprint varnish | 0.5–2.5% | Thin film usually easier to cure | Surface cure, gloss, blocking resistance |
| UV adhesive | 0.5–3.0% | Substrate transparency matters | Bond strength, depth cure, clarity |
| SLA/DLP resin | 0.2–2.0% | Match LED wavelength and resin color | Cure depth, resolution, brittleness |
| Thick-film UV system | 2.0–5.0% | More light absorption is needed | Bottom cure and mechanical strength |
For slow curing issues, compare your process against UVIXE’s guide on UV curing speed problems.
How Should You Test TPO-L Before Bulk Purchase?
A sample test should not stop at “the surface feels dry.” Surface cure can pass while through-cure fails. This is common in pigmented coatings, white UV ink, and thick resin systems.
When I support buyers, I ask them to record results in writing. A simple test sheet saves weeks of argument later.
TPO-L Validation Protocol
| Test | Why It Matters | What to Record |
|---|---|---|
| Surface tack | Checks surface cure | Finger touch, dust pickup, blocking |
| Through-cure | Checks bottom cure | Scratch, cross-section, or cure-depth result |
| Yellowing | Checks color stability | Before/after curing and aging |
| Adhesion | Checks substrate bond | Cross-hatch, peel, or customer method |
| MEK rub | Checks cure completeness | Number of rubs before film damage |
| Hardness | Checks final film performance | Pencil hardness or pendulum hardness |
| Odor | Checks incomplete cure or sensitive use risk | Odor after curing and after storage |
| Storage stability | Checks formula risk | Viscosity, color, and separation after aging |
| Line speed | Checks production value | Max speed before tack or under-cure appears |
For white systems, I always ask whether the buyer tested through-cure, not only surface tack. TiO₂ can make a formula look cured on top and weak below.
What Can Go Wrong When Using TPO-L?
TPO-L is useful, but it is not a cure-all. Most failures come from poor matching, weak testing, or incomplete supplier communication.
Common TPO-L Problems
- Under-cure: The LED wavelength or UV energy does not match the formula.
- Poor through-cure: Pigment or film thickness blocks light penetration.
- Surface tack: Oxygen inhibition or weak surface radical formation causes incomplete cure.
- Yellowing: Dosage, resin color, amine package, or overexposure creates visible color shift.
- Odor: Wrong dosage or incomplete cure leaves residual odor.
- Weak adhesion: The cured film does not bond well to substrate.
- Storage instability: Monomers, stabilizers, temperature, or contamination create formula drift.
- Customs delay: SDS, COA, TDS, or shipping information is incomplete.
If yellowing is your main issue, study UVIXE’s guide on photoinitiator yellowing in UV coatings before changing only one raw material.
TCO: Why TPO-L Price Alone Can Mislead Buyers
Many procurement teams ask for price per kg first. I understand that. But in UV curing, price per kg is only one part of the real cost.
A cheaper TPO-L can become expensive if it needs higher dosage, slows the line, fails cure-depth testing, causes yellowing, or ships with weak documents.
Simple TCO Example
If Supplier A is cheaper by $2/kg, that looks attractive. But if your formula needs 0.8% more dosage to reach the same cure result, the saving may disappear. If the slower cure also reduces line speed by 10%, the production loss can exceed the raw material saving.
If one 200 kg coating batch fails, the real cost includes resin, monomer, pigment, labor, machine time, cleaning, retesting, and delivery delay. The photoinitiator invoice is rarely the biggest loss. The failed batch is.
TPO-L Total Cost of Ownership Table
| Cost Factor | Low-Quality Buying Risk | Practical Buyer Check |
|---|---|---|
| Unit price | Cheap kg but unstable batch | Compare COA and trial result |
| Dosage | Higher loading cancels price saving | Test equal performance, not equal dosage |
| Cure speed | Slow cure reduces line output | Run line-speed test |
| Scrap rate | Tacky or yellow batch gets rejected | Test under real film thickness |
| Labor | Poor blending increases production work | Check liquid handling and mixing |
| Documentation | Missing SDS or COA delays approval | Confirm files before payment |
| Lead time | Late supply stops production | Ask stock and production schedule |
| Customs | Wrong paperwork creates clearance risk | Confirm label, packing, and shipping data early |
Procurement rule: Do not buy TPO-L from the lowest quote alone. Buy from the supplier who can prove curing fit, batch consistency, document readiness, and export discipline.
Compliance, SDS, COA, and Export Documents
For B2B buyers, TPO-L compliance is not a marketing phrase. It is a document workflow.
Before buying, ask your supplier for:
- COA with batch number
- SDS in the required language or format
- TDS with storage and use guidance
- Product label
- Shelf-life declaration
- Net weight and gross weight
- Packing list
- HS code confirmation
- Shipping condition
- REACH support if selling into Europe
- CLP classification support for EU-facing buyers
- RoHS support if your customer requires it
The European Commission explains that REACH regulation covers chemical registration, evaluation, authorisation, and restriction in the EU. ECHA explains that CLP regulation covers classification, labelling, and packaging of substances and mixtures.
Do not accept vague words like “export grade” or “safe material” without documents. European, Middle Eastern, Indian, Turkish, and Southeast Asian buyers may face customer audits or customs checks. If the paperwork fails, the shipment may wait even when the chemistry is correct.
How to Choose a Photoinitiator TPO-L Supplier
A reliable TPO-L supplier should reduce technical and procurement risk. A weak supplier only quotes a low price.
When I review a buyer request, I want to see the application first. A UV ink factory, a UV adhesive maker, and a DLP resin producer should not receive the same technical answer.
TPO-L Supplier Checklist
| Supplier Check | What to Ask | Why It Matters |
|---|---|---|
| Product identity | CAS 84434-11-7, chemical name, purity | Prevents wrong-material purchasing |
| Batch control | COA for each batch | Reduces quality variation |
| Technical files | SDS, TDS, COA | Supports audits, customs, and customer approval |
| Application support | Coating, ink, adhesive, resin experience | Helps avoid wrong dosage |
| Sample support | 100–500 g sample | Allows lab validation before bulk order |
| Packaging | Small pack, 25 kg drum, bulk option | Matches lab, pilot, and production scale |
| Export experience | EU, Middle East, India, Southeast Asia | Reduces logistics and document risk |
| Alternative supply | TPO, 819, 1173, 184 options | Helps backup formulation planning |
| Lead time | Stock or production schedule | Prevents factory stoppage |
| Communication | Clear answers on wavelength and formula | Shows technical ability |
If you are not sure whether TPO-L is the right starting point, use UVIXE as a photoinitiator selection for UV ink and UV coating sourcing partner before confirming bulk order.
My Practical Buying Advice
Here is how I would buy TPO-L if I were sitting on your procurement side.
First, I would not buy only because the CAS number matches. CAS confirms identity. It does not confirm curing speed, yellowing, storage stability, or export readiness.
Second, I would send the supplier five details:
- UV system type: coating, ink, adhesive, varnish, or resin
- Lamp wavelength: mercury, 365 nm, 385 nm, 395 nm, or 405 nm
- Film thickness or cure-depth target
- Pigment system, especially TiO₂ or carbon black
- Current photoinitiator and dosage
Third, I would test a sample before ordering drums. Small trials cost time. Failed production costs more.
Fourth, I would check documents before payment. COA, SDS, TDS, label, packing information, and shipping details should be clear before shipment.
Fifth, I would compare supply stability. A supplier who can ship one sample but cannot support repeated batch quality is not enough for industrial production.
Before You Ask for a TPO-L Quote
Before you ask for a TPO-L price, send your lamp wavelength, formula type, pigment load, and current photoinitiator. I can usually tell whether TPO-L is a reasonable starting point or whether TPO, 819, 1173, 184, or a blend may make more sense.
This saves time for both sides. It also prevents the most common mistake in photoinitiator sourcing: buying by name before checking the curing system.
FAQ About Photoinitiator TPO-L
What is Photoinitiator TPO-L used for?
Photoinitiator TPO-L is used in UV coatings, UV inks, UV adhesives, overprint varnishes, and photopolymer resins. It starts free-radical curing after exposure to UV or LED light.
What is the CAS number of TPO-L?
The CAS number of TPO-L is 84434-11-7. Buyers use this number to verify COA, SDS, TDS, customs documents, and chemical identity.
Is TPO-L a liquid photoinitiator?
Yes. TPO-L is a liquid phosphine oxide photoinitiator. This is one reason factories choose it over powder photoinitiators in dosing and blending processes.
Is TPO-L suitable for LED UV curing?
Yes, TPO-L can be tested in LED UV curing systems. Final performance depends on wavelength, resin system, pigment load, film thickness, dosage, and UV energy.
Is TPO-L suitable for UV LED 395 nm?
TPO-L can be tested under 395 nm LED systems, but you still need lab validation. Check cure depth, surface tack, yellowing, adhesion, and line speed before bulk use.
Is TPO-L better than TPO?
Not always. TPO may perform better in some curing systems. TPO-L is often chosen for liquid handling, easier blending, low-yellowing targets, and production convenience.
Can TPO-L replace TPO?
Sometimes, but not blindly. TPO-L and TPO have different physical forms and formulation behavior. Test dosage, cure depth, surface cure, yellowing, and mechanical properties before replacement.
What is the recommended dosage of TPO-L?
A broad industrial reference range is often 0.5–5 wt%, but the correct dosage depends on application, lamp energy, pigment, resin, and film thickness. Always validate in your own formula.
Is TPO-L used in white UV coatings and inks?
Yes, TPO-L is often tested in white and pigmented UV systems. Titanium dioxide can block UV light, so through-cure testing is important.
What is the difference between TPO-L and 819?
TPO-L is a liquid phosphine oxide photoinitiator often used for liquid handling and low-yellowing systems. 819, also known as BAPO, is often considered for deep cure and pigmented systems. The better choice depends on color, film thickness, lamp, and cure target.
Can TPO-L be used in food packaging ink?
Do not assume it is suitable without migration, odor, regulatory, and customer-specific testing. Food packaging ink requires strict formulation review and compliance confirmation.
How should TPO-L be stored?
Store TPO-L in tightly closed original packaging, away from direct light, heat, and incompatible materials. Always follow the supplier SDS and TDS.
What sample size should buyers request before bulk order?
For early lab tests, many buyers request 100–500 g. For pilot trials, ask the supplier for a larger sample based on your batch size and testing plan.
What documents should I request before buying TPO-L?
Request COA, SDS, TDS, batch number, packing list, storage guidance, REACH support if needed, and export documents for your destination market.
Final Buying Note: TPO-L Is a Formula Decision, Not Just a CAS Number
Photoinitiator TPO-L is a liquid Type I phosphine oxide photoinitiator for industrial UV curing. It is useful in coatings, inks, adhesives, varnishes, and photopolymer resins where liquid handling, low-yellowing performance, and LED UV validation matter.
But the correct decision depends on your real production conditions. Lamp wavelength, pigment load, film thickness, dosage, resin chemistry, cure speed, compliance documents, and supplier stability all matter.
My advice is simple: do not buy TPO-L only as a chemical name. Buy it as part of a validated curing system.
Send Your UV Line Details Before You Buy TPO-L
If you are sourcing TPO-L for UV coating, UV ink, UV adhesive, or photopolymer resin production, UVIXE can help you check the basic match before you order.
Send us:
- Application type
- Resin or monomer system
- Lamp wavelength
- Film thickness or cure-depth target
- Pigment type and loading
- Current photoinitiator and dosage
- Target market
- Sample quantity or annual volume
UVIXE can support industrial buyers with Photoinitiator TPO-L supplier information, COA, SDS, TDS, sample discussion, packaging details, lead time, and FOB China quotation.