Novel bio-based flame retardant systems derived from tannic acid

Abstract

In this study, tannic acid (TA) was investigated as flame retardant agent for PLA. Different strategies to modify its thermal degradation pathway have been explored in order to improve its charring effect. The first one consists in combining TA with organomodified montmorillonite (oMMT), and enables limiting the thermo-oxidative degradation of TA and promoting the formation of an effective char layer. Flame-retardant (FR) behavior of PLA-based composition has been found to be positively impacted by this combination since a reduction of the peak of Heat Release Rate (PHRR), more important than the value recorded when oMMT and tannic acid are used separately, has been obtained. The second strategy, in which tannic acid was associated with a biosourced phosphorous-based compounds, i.e. metallic phytate salt, evidenced another alternative allowing enhancing TA flame retardant effect at 30 wt% loading content. The third and last strategy explored aims to chemically modify TA via a chemical grafting of phosphoric acid groups. This phosphorylated TA was shown to present the most effective flame-retardant (FR) effect. However, an important reduction of PLA molecular weight was observed.