Effect of LbL Deposited Chitosan-Nanosilica Bilayers on Flammability and Thermal Properties of Polylactide Materials

The present work is devoted to studying the effect of the synergistic action of Si-O-Si and NH-CO groups on the flammability and thermal properties of polylactide (PLA). For this purpose, using the Layer-by-Layer (LbL) technique, 5, 10, and 15 bilayers of chitosan (CS) and nanosilica (NS) were deposited onto the surface of PLA and PLA/NS composite (PLA/A200). More than a 20% reduction in flammability was achieved (sample (15BL) PLA/A200). Studying the effect of LbL-deposited bilayers on two types of surfaces, an identical relationship was found: the more layers adsorbed, the lower thermal stability, and vice versa the more layers, the higher flame retardancy. In turn, the lower the thermal stability, the faster the ability to form char, and the more solid residue, the lower the flammability and longer the burning time. This means that the application of CS-NS bilayers results in decomposition reactions in the condensed phase, which reduces the amount of flammable released.