Effects of Bio-Based Polyelectrolyte Complex on Thermal Stability, Flammability, and Mechanical Properties Performance Utilization in PLA/PBS Composites

In this study, the two eco-friendly flame retardants of the polymeric type (PA-PEI) and monomeric type (PA-Arg) phytate amine complexes were prepared via the ionic reaction of polyethylenimine (PEI) or arginine (Arg), respectively, with phytic acid in an aqueous solution. The chemical structure and thermal stability of PA-PEI and PA-Arg were characterized by Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). In order to improve the flame retardancy of the polylactic acid (PLA)/polybutylene succinate (PBS) biocomposites (P/15B-based biocomposites), the flame retardants PA-PEI and PA-Arg were embedded into P/15B by thermal blending procedures, respectively, to obtain P/15B/PA-PEI series and P/15B/PA-Arg series biocomposites. The TGA analyses demonstrated that incorporating PA-PEI or PA-Arg into the P/15B polymer enhances the char residues in these P/15B biocomposites. The XRD and SEM analyses of the P/15B/PA-PEI series and P/15B/PA-Arg series suggested the PA-PEI and PA-Arg were embedded into the P/15B polymer matrixes, respectively. The mechanical results showed that P/15B/PA-Arg series exhibited higher values than the P/15B/PA-PEI series biocomposite, which were associated with less roughness of P/15B/PA-Arg than that of the P/15B/PA-PEI series. The flammability results of the P/15B/PA-PEI series and P/15B/PA-Arg series biocomposites exhibited a V-2 level in UL94 vertical test. Further, the fire resistance performance of P/15B-based biocomposites was enhanced by incorporating PA-PEI or PA-Arg into the P/15B matrix through the analyses of the Cone calorimeter test (CCT), as a comparison with neat P/15B. The peak heat release rate (pHRR), the total heat release rate (THR), and char residues of P/15B/15PA-Arg biocomposite were significantly improved to 280.26 kW/m², 107.89 MJ/m², and 10.4%, respectively. The enhancement of the P/15B-based composites’ fire resistance is attributed to the interplay effect on the catalytic and condensed effect on the thermal decomposition of PA-PEI or PA-Arg in P/15B biocomposites. The resultant eco-friendly flame-retardant P/15B biocomposites reported in this study can be widely applied in various fields, including construction, electronic appliances, and other fields.

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