Biodegradable thermochromic polylactic acid (PLA) sensor

Abstract This study investigates the development of polylactic acid (PLA) by incorporating thermochromic black pigments (TCB) at varying concentrations of 0, 0.5, 1, 2 and 3 wt% through the process of melt blending. The color transition and reversion behaviors of the resulting specimens were examined at different temperatures (−10, 10, 30, 35 and 50 °C) using colorimetric analysis. Additionally, mechanical properties, thermal characteristic and thermal stability were assessed through tensile testing, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The study revealed that an increase in TCB concentrations led to a reduction in lightness (L*). Higher pigment content enhanced thermochromic properties, resulting in more pronounced color changes. The total color difference (ΔE) remained reproducible over five cycles of heating and freezing, and this reproducibility persisted after thermal aging. Tensile strength and elongation at break exhibited improvement with increasing pigment content. Glass transition temperature (T g ) and melting temperature (T m ) of the thermochromic samples showed minimal reduction compared to that of neat PLA, which is 64.2 °C. Crystallinity degree (X c ) increased slightly by 0.2–0.92 %. The thermal stability of the PLA matrix was only marginally affected by the presence of thermochromic pigments.