BPA Free Thermochromic Powder Rose Red 31°C KTP-31-PBF

This is a microencapsulated leuco dye system — rose red in its resting state, colorless above 31°C. The color transition is fully reversible. Cool the substrate below the activation threshold, the rose red returns. Raise it above, it disappears — cleanly, with no intermediate haze in a well-formulated system.

The BPA Free designation isn't a marketing label here. It reflects a real formulation change in the encapsulation chemistry that makes this series suitable for applications where conventional thermochromic pigments — which may contain bisphenol A as a color developer — would be restricted. That includes food-contact surfaces and cosmetic use cases subject to regulatory scrutiny.

Particle size runs 3–10μm, which is compatible with most coating, printing, and cosmetic dispersion processes without requiring unusual milling steps.

Product Series — BPA Free, 31°C Activation Range

KTP-31-PBF is part of a broader BPA Free lineup. All variants listed below are Colored to Colorless and share the same 3–10μm particle size. The activation temperature range covers 30–32°C depending on the grade selected.

If your application calls for a color-to-color transition rather than color-to-colorless, Kolortek also offers a separate Colored To Another Colored series — ask for those models specifically when requesting samples.

Applications

The 31°C activation temperature puts this pigment squarely in the body-temperature-sensitive range, which opens up a specific set of use cases that lower-temperature grades don't serve as cleanly.

• Cosmetics & Nail Systems: The BPA Free status satisfies formulation requirements for leave-on cosmetic products. Works in nail lacquers and nail gels — skin contact activates the transition.
• Food-Contact Printing & Coatings: Suitable for cups, spoons, and packaging where ink or coating contacts food or beverages. The BPA Free series is the correct choice here — standard thermochromic grades are not.
• Hair Coloring Products: Used in heat-responsive hair color formulations where color change signals temperature proximity.
• Textile Printing: Integrates into screen and digital printing workflows for apparel or functional textiles requiring heat-reactive color behavior.
• Custom Paint & Craft Art: Compatible with water-based and solvent-based paint systems for novelty, art, and decorative applications.
• Paints & Coatings: Suitable for architectural and decorative coatings. Worth noting: this series is not recommended for automotive topcoat applications due to processing temperature and UV exposure constraints.

Key Characteristics

A few things that matter in practice when specifying or formulating with KTP-31-PBF:

• Reversible transition: The color-to-colorless shift is fully reversible under normal use conditions. No permanent color change occurs from standard thermal cycling.
• BPA Free encapsulation: The microcapsule shell and color-developer chemistry are formulated without bisphenol A — critical for cosmetic and food-contact compliance.
• Colored to Colorless mechanism: Above 31°C, the rose red color disappears. The underlying substrate, base coat, or print layer becomes visible. Design around this: choose your base color deliberately, as it defines the "activated" appearance.
• Batch-to-batch consistency: Kolortek's ISO9001-certified production system ensures the activation temperature and color depth remain stable across production lots — relevant if you're scaling from sampling to production volumes.
• Documentation available: MSDS, TDS, and COA are available on request. Formulation guidelines support can be provided for complex system integration.

Practical Formulation Considerations

Thermochromic pigments are microencapsulated — the capsule is the functional element, not just a carrier. That has direct implications for how you handle them in your process.

Avoid high-shear dispersion. Aggressive milling or rotor-stator mixing above recommended shear thresholds can rupture the microcapsules, permanently degrading the thermochromic response. Pre-disperse in a compatible carrier at low shear, then let down into your system.

Processing temperatures matter. If your ink, coating, or resin system requires elevated temperature curing or processing — particularly above 80°C — test compatibility carefully. Sustained high-temperature exposure can compromise both the encapsulation integrity and the leuco dye system.

In practice, aqueous systems tend to be more straightforward. Solvent-based systems work but require verification that the solvent doesn't interact with the capsule wall. Request the TDS for carrier and solvent compatibility guidance before committing to a formulation direction.

That said, the thermochromic powder itself is a dry, free-flowing powder — it disperses cleanly into a range of vehicles when handled correctly. Loading levels typically run 5–15% depending on the application and the depth of color shift effect required.

BPA Free vs. Standard Thermochromic — When It Matters

Standard leuco dye thermochromic systems commonly use bisphenol A as the color developer component. For applications such as toy packaging, food utensils, cosmetics, and children's products, that's a regulatory problem in most major markets.

The BPA Free series substitutes an alternative color developer that achieves the same reversible thermochromic function without BPA. The trade-off — if any — is typically minimal in terms of color intensity and transition sharpness at the 31°C range, but formulators should always run their own application-specific performance validation.

If your application doesn't involve food contact, cosmetics, or sensitive end-use markets, the standard series may offer a broader color range. If it does, BPA Free is the only appropriate starting point.

Frequently Asked Questions

Q: Is KTP-31-PBF suitable for direct food contact applications?
A: Yes. The BPA Free designation means this series is formulated for use in food-contact applications such as coated cups, printed spoons, and similar items. It is the appropriate grade for those applications — the standard thermochromic series is not.

Q: What base coat color should I use underneath this pigment in a Colored to Colorless system?
A: That depends entirely on your design intent. When the pigment activates above 31°C and becomes colorless, whatever is underneath becomes visible. A white base reads as "blank." A colored base creates an apparent color change from rose red to that base color. Plan your substrate or base coat as an active design element, not a background.

Q: Can this pigment be used in UV-curable ink systems?
A: It requires careful validation. UV curing processes can involve brief but intense energy exposure. The key concern is whether the UV dose and any associated heat spike compromise capsule integrity. Some UV ink systems are compatible; others are not. Testing under your specific cure conditions is necessary before committing to production.

Q: Are samples and technical documentation available before placing a bulk order?
A: Yes. Samples, TDS, MSDS, and COA are available on request. Formulation support can also be arranged. Contact contact@kolortek.com with your application details to get the right documentation and sample quantity for your evaluation.

To request samples of KTP-31-PBF or any BPA Free thermochromic grade, or to discuss formulation compatibility for your specific substrate and process, contact the Kolortek technical team at contact@kolortek.com. Provide your application, carrier system, and processing conditions for a faster, more targeted response.