Analysis of the Degradation of Thermochromic Sensors in Electrical Devices

Abstract

Thermochromic materials exhibit color changes with temperature variations. Leuco dyes, composed of a color former, developer, and solvent, are microencapsulated in polymeric shells to preserve their thermochromic function. Their use in diverse applications requires understanding their performance and degradation under environmental conditions. This study investigates the degradability of reversible thermochromic pigments in their pure form and embedded in an epoxy matrix, simulating conditions relevant to temperature sensors in electrical networks. Samples were subjected to accelerated weathering, thermal exposure, and cyclic thermal exposure to evaluate their stability and aging. The samples were characterized by colorimetry, SEM, optical microscopy, and DSC/TG analyses. Results indicated more severe degradation in samples exposed to weathering, evidenced by greater total color variation and loss of reversibility, which is likely caused by microcapsule cracking and solvent loss. The findings demonstrate that temperature alone does not significantly promote pigment degradation, whereas UV radiation strongly compromises thermochromic stability. Therefore, applications requiring long-term UV exposure demand a more resistant polymeric encapsulation than epoxy resin to ensure durability and maintain thermochromic functionality.