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Coloration of the polylactic acid with the natural dye extracted from acacia cyanophylla flowers

The use of synthetic dyes in food packaging disrupts the environment and human health, to solve this problem we use natural dyes. The aim of this paper is to study the coloration of a biopolymer such as the PLA 5200 D with a natural dye extracted from Acacia cyanophylla flowers. The biodegradable colored material was prepared using an internal mixer and the influence of the implementation parameters such as temperature, rotor speed and mixing time has been studied. The chemical structure of the dye was confirmed by Fourier Transform Infrared spectroscopy (FTIR) and UV-spectroscopy. Thermal properties of the samples were performed using Differential Scanning Calorimetric (DSC) and Thermo Gravimetric Analysis (TGA). The coloring of the polymer (darker yellowing) was studied to quantify the dye in the mixture. The aging of the colored material was followed by colorimetric analysis after its exposure under UV lamps. The results show that the dye remains stable until 130?°C and when the temperature goes up to 160?°C, the dye is crystallizing. The degradation was observed at 190?°C. A good elaborate colored material was promoted for a 50?rpm blending during 5?min?at 90?°C and with a concentration of die of 0.5% in the internal mixer.

Aging tests show that the material remained almost stable after one week under UV radiations.

Publication date: 01/09/2019

Author: Afef Fajraoui, Jalel Ben Nasr, Catherine Lacoste, Mohamed Ben Amar, Philippe Dony, Serge Odof, Foued El Halouani

Polymer Testing


This project has received funding from the Bio Based Industries Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 837761.