Phytic acid–lignin combination: A simple and efficient route for enhancing thermal and flame retardant properties of polylactide

Lignin and phytic acid combinations were used as a simple route for developing bio-based flame retardant systems in PLA. The composites were prepared by melt blending and their mechanical, thermal and fire properties have been explored. Combining these two additives has been shown to present an interesting way of limiting the negative effect of each of them and for improving the properties of the resulting materials. On the first hand, the presence of phytic acid enables better dispersion of lignin particles into the matrix, limiting PLA thermal degradation induced by lignin. On the second hand, lignin enables important reduction of the composite hygroscopy induced by the presence of phytic acid. Moreover, combining lignin and phytic acid leads to significant reduction up to 44% of peak of heat release rate (pHRR) during cone calorimeter test as well as obtaining V-2 classification in UL-94 test. Some positive effects of the binary combinations on the composites mechanical properties have also been evidenced (increase of the elongation at break from 3.1% to 12.6% for one formulation).