PIGMENT & RESIN TECHNOLOGY, cilt.49, ss.273-281, 2020 (SCI İndekslerine Giren Dergi)
PIGMENT & RESIN TECHNOLOGY
Purpose – Stimulant-sensitive materials exhibit physical or chemical reversible changes in their properties as a result of environmental variables. One of these materials is thermochromic materials. Materials with thermochromic sensitivity change their color with heat exchange. For this reason, it can be used in many different fields such as security inks. Such substances decompose rapidly by being affected by weather conditions. Furthermore, the particle sizes are larger than normal pigments and therefore it is difficult to stabilize thermochromic dyes. Because of all these adverse conditions, thermochromic colorants must be protected before use in the ink. This protection is planned to be provided by microcapsulation technique. The aim of this study is to determine the thermochromic printing inks that can be stored stably by microcapsulation technique, to protect it from environmental conditions and determination of printability parameters.
Design/methodology/approach – In this study, capsules with a core material of thermochromic dyeing with polyurea formaldehyde (PUF) or poly-phenolmelamine formaldehyde (PMF) shell were synthesized at appropriate pH and temperature using the appropriate solvent and mixing speed. The chemical structure and dimensions of the obtained capsules were examined by ATR-FTIR and SEM, respectively. The produced thermochromic microcapsules were mixed with alkyd resin and mineral oil and screen printing ink was obtained. Printability tests such as surface morphology, color, gloss and lightfastness were applied.
Findings - As a result, it was determined that PMF is not a suitable encapsulation technique for thermochromic dyes under suitable conditions and eliminates thermochromic property by providing heat stability. It was found that PUF microcapsulation can be used in thermochromic dyestuff encapsulation and does not lose thermochromic property. It has also been found that PUF microcapsules increases the lightfastness and stability of thermochromic dye ink.
Originality/value - This article provides an experimental research on the encapsulation of a thermochromic dye and its use in ink.