Enhanced Flame Retardancy, Ultraviolet Shielding, and Preserved Mechanical Properties of Polylactic Acid with Fully Biobased Multifunctional Additives by a Green Method

Flammability, slow nucleation rates, and poor UV-shielding limit the widespread use of the bioplastic polylactic acid (PLA). Traditional functional additives usually have the disadvantages of complicated synthesis process, environmental unfriendliness, single function, etc., and after blending with PLA, it will also lead to the degradation of mechanical properties. In this work, fully biobased multifunctional additives (PN) were prepared by a simple and green aqueous phase electrostatic self-assembly method using biobased phytic acid and nicotinamide as monomers. Incorporation of only 2 wt % PN endowed PLA with the limiting oxygen index of 29.0% and the UL-94 rating of V-0, meeting the standard for flame-retardant materials. Flame-retardant mechanisms of PLA/PN composites were mainly gas phase. In addition, the UV protection factor value of PLA was increased to 90.8, showing good UV shielding ability. It was noteworthy that the incorporation of PN increased the nucleation density of PLA, thus maintaining better mechanical properties of PLA. Therefore, this work provides a green and efficient method for the large-scale preparation of fully biobased multifunctional additives, which is expected to expand the application areas of PLA.