UV Curable Resins
Line speed is an output, not an input. Start from irradiance, wavelength and film thickness, then derive the speed your process can actually hold.
Cure dose (mJ/cm²) = irradiance (W/cm²) × exposure time. Exposure time is the dwell under the lamp, derived from line speed: time = lamp length ÷ line speed. The irradiance must be measured at the substrate surface with a calibrated radiometer — not the lamp's nameplate. Match the lamp spectrum to the photoinitiator package: LED systems run at 365, 385, 395 or 405 nm, and a spectral mismatch silently drops conversion.
| Parameter | Typical range | Common test method |
|---|---|---|
| UV/LED cure dose | 100–2,000 mJ/cm² (depends on wavelength/thickness) | Internal (cure end-point) |
| Irradiance at surface | 0.5–4 W/cm² | Calibrated radiometer |
| Cure wavelength | 365 / 385 / 395 / 405 nm | Internal |
| Viscosity | 50–50,000 mPa·s | ASTM D2196; ISO 2555 |
| Shore D hardness | 50–85 | ASTM D2240; ISO 868 |
| Pencil hardness | H–6H | ASTM D3363; ISO 15184 |
| Adhesion to metal / glass / PET | 0–1 (ISO) / 4B–5B (ASTM) | ISO 2409; ASTM D3359 |
| Volumetric shrinkage | 2–10 % | Internal |
| Yellowing index (ΔYI after aging) | ≤3–10 | ASTM E313 |
Our WJX-500 UV diluent and PET UV resin are supplied with TDS values for viscosity, solids and recommended cure energy.
| Factor | UV LED | Mercury |
|---|---|---|
| Spectrum | Narrow, tunable (365–405 nm) | Broad, includes shorter UV |
| Heat load | Lower | Higher |
| Lamp life | Long | Shorter |
| Photoinitiator match | Must match LED wavelengths | Broader absorption tolerated |
| Failure | Root cause | Corrective |
|---|---|---|
| Surface tacky | Oxygen inhibition, under-dose, wrong initiator | Raise effective dose; match spectrum; inerting or surface cure strategy |
| Poor metal/glass adhesion | Contamination, low surface energy, resin mismatch | Clean pretreatment + compatible primer/formulation |
| Incomplete through-cure | Film too thick, pigment absorption, poor UV penetration | Reduce thickness; adjust initiator; staged/complementary curing |
| Cracking / brittle film | Crosslink density too high; substrate movement | More flexible oligomer; reduce thickness; optimize cure |
| Yellowing | Initiator choice; over-exposure; heat degradation | Low-yellowing system; optimize spectrum/dose/temperature |
Dose (mJ/cm²) equals irradiance (W/cm² measured at the substrate surface with a calibrated radiometer) multiplied by exposure time, which is line speed converted to dwell time under the lamp. Match the lamp spectrum to the photoinitiator absorption.
Oxygen inhibition and spectral mismatch can leave the underlying layer uncured while the surface feels dry. Measure cure depth and degree of conversion separately; a surface-only check hides incomplete through-cure.
LED offers a narrow, tunable spectrum, lower heat load and long life, but needs photoinitiators matched to those wavelengths. Mercury emits a broader spectrum at higher heat and shorter lamp life. The choice is formulation- and substrate-dependent.
Thicker or pigmented/high-absorption films need more dose or a complementary curing strategy because UV penetration is limited. Build the process window from film thickness, adhesion, hardness and degree of conversion rather than line speed alone.
Share your substrate, lamp type, film thickness and target line speed. We'll recommend a resin/diluent pairing and cure window, with TDS on request.
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