Fluorescent Pigments: A Technical Guide to Series Selection and Use

1. What Makes a Pigment "Fluorescent"?

A conventional pigment only reflects part of the daylight that falls on it. A daylight fluorescent pigment does something more: it absorbs invisible ultraviolet light — and part of the shorter visible wavelengths — and converts that energy into visible light emitted in its own color band. The eye therefore receives the normally reflected light plus this converted fluorescent light, which is why fluorescent colors appear strikingly brighter and more saturated than conventional colors under daylight.

Technically, a daylight fluorescent pigment is not a single chemical but a colored resin particle: fluorescent dyes are dissolved in a resin matrix (a solid solution) and the colored resin is milled into a fine powder. The resin carrier is what the application actually "sees" during processing — which is why fluorescent pigments are organized into series by resin type, and why series selection matters as much as color selection.

2. Two Resin Families, Seven Series

Deping's fluorescent pigments come in seven series. The thermoplastic series soften and melt on heating; the thermoset series do not melt and keep their particle form during processing.

The main color range covers chartreuse, green, yellow, orange yellow, orange, red orange, red, cerise, pink, magenta, violet and blue shades. A few colors are series-specific: royal blue and strong magenta are available in the DX series only, white and clear in the DP series only, and some shades are not offered in the DZ/DQ series — please refer to the color chart and TDS for the exact availability of a given shade.

3. Selecting a Series by Application

• Injection molding and extrusion (PP, PE, PET, PVC): Start with DX or DZ. The decisive check is processing temperature: keep the melt temperature within the heat resistance of the series — for DX, the limit is 195 °C (see Section 4).
• Water-based color pastes and water-based coatings: DX is the series listed for water-based coatings.
• Powder coatings: DZ, DP and DFQ are the series listed for powder coating. Check that the curing schedule of the coating stays within the pigment's heat resistance.
• Inks and paints: DP and DFB are the ink- and paint-oriented series; DFQ also covers inks and coatings.
• Masterbatch and blow molding: DQ is designed for blow-molded bottles and masterbatch; DFQ can also be used in masterbatch.
• Rubber, TPR and EVA: DFL is the series for these elastomer applications.

4. Key Properties — and Honest Limitations

Heat resistance

Heat resistance is series-dependent and is a hard ceiling, not a guideline. The DX series withstands up to 195 °C, which suits injection molding in the usual processing window below that temperature. Processing above a series' limit degrades the fluorescent dye: brightness drops and the shade shifts. Always work to the temperature limit in the TDS of the series you use.

Light fastness — the inherent limitation

Daylight fluorescent pigments are, by nature, markedly less lightfast than conventional pigments: the same fluorescent dyes that produce the brilliance are progressively broken down by sunlight, so colors fade with prolonged outdoor exposure. This applies to fluorescent pigments from every manufacturer. They are therefore best suited to indoor applications, short-life and promotional articles, toys, and safety or marking uses where maximum brightness matters more than permanence. For outdoor use, run exposure trials first and set expectations accordingly.

Solvent resistance and migration

Because the colorant is a dye dissolved in a resin, fluorescent pigments can bleed in strong solvent systems and migrate in highly plasticized plastics. Compatibility must be tested in the actual formulation before production, especially for solvent-based inks and coatings and for plasticized PVC.

5. Processing Notes

• Temperature discipline comes first: stay below the heat-resistance ceiling of the series (DX: 195 °C) and avoid unnecessarily long residence time at temperature.
• Disperse gently but completely: use the mildest mixing conditions that develop the full color; the pigment develops its brightness when evenly distributed, and abusive processing only costs fluorescence.
• In powder coatings: incorporate the pigment by the method given in the TDS and confirm the curing schedule stays within the pigment's heat resistance.
• Test before production: check shade, brightness, bleed and migration in the real system — especially with solvent-based media and plasticized plastics.
• Storage: keep the pigment cool, dry and out of direct sunlight to protect its brightness.

6. Frequently Asked Questions

Q1: Why do fluorescent colors fade outdoors?

Because the fluorescent dyes themselves are sensitive to sunlight: ultraviolet exposure progressively destroys the dye molecules that produce fluorescence, so brightness and then color are lost. This is an inherent property of all daylight fluorescent pigments, not a quality defect. Fluorescent pigments are best used indoors or in applications with a limited service life outdoors; for outdoor use, verify the fading behavior with exposure tests in advance.

Q2: Which fluorescent pigment series can be used in powder coatings?

Three Deping series are listed for powder coatings: DZ (thermoplastic), DP and DFQ (thermoset). Whichever you choose, confirm that the coating's curing schedule stays within the pigment's heat resistance, because the pigment has to survive the full curing cycle without losing brightness.

Q3: What is the maximum processing temperature for the DX series in injection molding?

The DX series has a heat resistance of up to 195 °C, so melt temperature and residence time must be kept within that limit, as stated in the TDS. Processing hotter than the limit degrades the fluorescent dye and shows up as lost brightness and shade shift in the molded part.