Blue BPA Free Thermochromic Pigment, Food Grade 31°C, 3–10μm – KTP-31-BBF

Blue BPA Free Thermochromic Pigment, Food Grade 31°C, 3–10μm – KTP-31-BBF

Special Effect Pigments › Thermochromic Pigment Series › BPA Free Food Grade

KTP-31-BBF is a Blue BPA Free thermochromic pigment with a 31°C activation temperature in the fine 3–10μm particle size range — a food-grade Colored-to-Colorless (C2CL) microencapsulated leuco dye pigment that is blue below 31°C and becomes colorless as temperature rises above the threshold. The BPA Free formulation places KTP-31-BBF in Kolortek's food-grade thermochromic series, which uses capsule chemistry that eliminates bisphenol A (BPA) — a standard procurement requirement for food packaging, beverage containers, children's products, and applications where indirect or incidental food contact is a regulatory consideration. At 3–10μm, it processes in printing inks and coatings without visible surface texture in cured films.

Why BPA Free Matters — Procurement and Regulatory Context

Standard thermochromic leuco dye systems use bisphenol A as part of the color-former chemistry within the microcapsule. BPA is regulated or restricted in food contact materials in the EU (EC 10/2011), USA (FDA, state-level restrictions), and other markets — its presence in thermochromic inks on food packaging or beverage containers can create compliance issues even when the BPA is encapsulated, depending on migration testing requirements and the regulatory interpretation applied to the specific application.

KTP-31-BBF uses a BPA-free substitute in the leuco dye system, removing BPA from the capsule chemistry entirely. For procurement teams sourcing thermochromic pigments for food-adjacent applications, this eliminates the BPA-related compliance question rather than requiring migration testing to establish a case for compliance. Where BPA Free is the specification — whether driven by regulation, brand policy, retailer requirement, or certification framework — KTP-31-BBF is the appropriate grade. Where BPA Free is not a requirement, the standard KTP-31 series provides equivalent performance at lower cost.

Kolortek BPA Free Thermochromic Series — Available Colors at 31°C

All BPA Free grades are Colored-to-Colorless (C2CL) — colored in the cold state, colorless above activation temperature. The warm-state visual is determined by the substrate or base coat beneath. Contact Kolortek to confirm current BPA Free grade availability and for documentation supporting food contact compliance requirements.

Technical Specifications

Key Technical Characteristics

BPA Free capsule chemistry — what changes and what stays the same: In a standard thermochromic leuco dye system, BPA functions as the color developer within the capsule — it protonates the leuco dye in the cold state to produce the colored form and releases it in the warm state to allow the colorless form to dominate. BPA Free grades substitute an alternative developer compound that provides the same pH-dependent color switching mechanism without using bisphenol A. The thermochromic function — including activation temperature, reversibility, and color-to-colorless change type — is preserved. The performance difference between BPA Free and standard grades is typically a minor reduction in color intensity or transition sharpness, which varies by color and specific formulation. Request samples for bench comparison before specifying for high-volume production.

31°C — body temperature activation and its design implications: KTP-31-BBF becomes colorless when temperature rises through 31°C — a threshold that corresponds to warm skin contact, body warmth, and warm handling conditions. At typical room temperature (20–25°C), it remains blue. The color disappears when held in warm hands, used in body-temperature contact applications, or exposed to warm liquids. For cold beverage packaging, the blue indicator signals "cold" and disappears at hand-warm temperature — a clean visual cold-indicator using body heat as the trigger. For cosmetic applications, the shift occurs during product wear on skin.

Designing the warm state — base coat is the second half of the design: KTP-31-BBF becomes colorless above 31°C, which means the warm-state visual depends entirely on what is beneath the thermochromic ink layer. A white substrate produces white at warm temperatures. A blue base coat produces blue at both temperatures with no visible change at the distance where the thermochromic layer is blue on top. A contrasting design — printed text or graphic in a different color beneath — is revealed when the thermochromic blue layer becomes transparent above 31°C. The warm-state design is as important as the thermochromic pigment specification — both must be planned together.

Low-shear processing is non-negotiable: The BPA Free microencapsule in KTP-31-BBF has the same mechanical sensitivity as standard thermochromic grades. High-shear dispersion, ball milling, three-roll milling, and tight-clearance pump recirculation all rupture capsule walls and permanently destroy the thermochromic function. Add KTP-31-BBF at the final mixing stage using low-shear paddle or anchor mixing, after all other dispersion steps are complete. Kolortek has maintained consistent BPA Free capsule quality and activation temperature calibration across production batches for over 20 years. BPA Free certification documentation is available on request.

Application Range

Frequently Asked Questions

Q: Does BPA Free mean KTP-31-BBF is approved for direct food contact?
A: BPA Free describes the capsule chemistry — it means bisphenol A is not used in the pigment formulation. It does not automatically confer regulatory approval for direct food contact in all markets and applications. Compliance for direct food contact printing inks also depends on the complete ink formulation (binder, solvents, other additives), the specific food contact regulation applicable in your target market (EU 10/2011, FDA 21 CFR, etc.), and migration testing where required. BPA Free is one component of a food contact compliance assessment, not the whole assessment. Contact Kolortek for the available documentation, and verify the complete compliance requirement with your regulatory affairs team for your specific application and market.

Q: Is the blue color of KTP-31-BBF identical to the standard grade KTP-31-SB Sapphire Blue?
A: KTP-31-SB (Sapphire Blue, standard grade) and KTP-31-BBF (Blue, BPA Free) are both blue thermochromic grades at 31°C, but they are separate product formulations with potentially different blue hue characteristics. The BPA Free developer compound can produce a slightly different color saturation or hue bias compared to the BPA-based equivalent. Request physical samples of both grades for drawdown comparison in your specific ink or coating system before specifying for production, particularly if color matching to a specific blue standard is a requirement.

Q: What documentation does Kolortek provide to support BPA Free claims?
A: Kolortek provides TDS and SDS for KTP-31-BBF, along with BPA Free certification documentation on request. For applications requiring specific regulatory documentation — EU EC 10/2011 declarations, FDA compliance letters, migration test reports — contact Kolortek's technical team to discuss what is available and whether additional third-party testing is required for your specific application and market.

Q: Are there BPA Free thermochromic grades at other activation temperatures?
A: The current Kolortek BPA Free series is centered at the 31°C body-temperature activation range, with KTP-30-SBF (Sapphire Blue, 30°C) and KTP-32-BY F (Yellow, 32°C) offering near-31°C alternatives. BPA Free grades at the cold-indicator activation temperatures (16°C, 18°C) or hot-indicator temperatures (43°C, 45°C) are not currently listed in the standard range. Contact Kolortek to discuss custom activation temperature requirements for BPA Free grades.

Request Samples or BPA Free Documentation

If BPA Free thermochromic pigment is a specification requirement for your application, contact Kolortek to request a sample of KTP-31-BBF alongside other BPA Free series colors, download the TDS, or request the BPA Free certification documentation needed for your supplier qualification or regulatory compliance file.