Historically Inspired Strategy to Achieve Sustainable and Effective Coloration of Bioplastics

Abstract

The use of historical organic pigments is an interesting strategy to provide color nuances to biopolymers while achieving good solid optical effects. In this work, aqueous extracts of logwood (LW) are tested as a natural source of color for the sustainable production of an organic purple pigment (LWP) taking advantage of the historical lake approach. Different amounts of LWP (0.01–2% wt) are used for the effective coloration of polycaprolactone (PCL), polybutylene succinate (PBS), and polylactide (PLA). The full characterization of LWP and LWP-treated biopolymer samples enables the spectral and color properties of the composites to be defined where the exceptional color efficiency of LWP is demonstrated by the very low amount (0.5% wt) necessary to reach the saturation. The evolution of spectra and color coordinates under accelerated aging conditions is monitored for LWP-polymer samples. A 10–12% decrease of the visible absorption band is detected after prolonged irradiation, resulting in a moderate color fading for PBS compared to PCL samples, while negligible changes are observed for PLA samples. The results demonstrate that LWP constitutes an efficient and sustainable source of color for the analyzed polymers without causing significant changes in the tensile and thermal properties of the polymeric matrix.