Effect of P3O105− intercalated hydrotalcite on the flame retardant properties and the degradation mechanism of a novel polypropylene/hydrotalcite system

Abstract P3O105− intercalated Mg/Al hydrotalcite (LDH-P) was successfully prepared by impregnation-reconstruction, and its microstructure and surface chemical properties were characterized. It was found that P3O105− anion has completely intercalated into the interlayer space of the LDH-P. And the LDH-P exhibited a higher dispersity and weaker hydrophobicity than the CO32– intercalated Mg/Al hydrotalcite (LDH-C). The LDH-P was investigated as a potential flame retardant for polypropylene (PP) matrix, then the LDH-P and PP composite (PP/LDH-P) was characterized using X-ray diffraction (XRD) and thermogravimetric analysis (TGA) as well as the limited oxygen index (LOI), vertical burning UL94 and mechanical test, the results revealed that the introduction of LDH-P into PP not only increased the char residue, but also formed compact and folded morphology of char residue providing more effective protection for underlying materials against heat and oxygen compare with LDH-C. The morphological structures and component observed by digital photos, scanning electron micrograph (SEM) and Fourier transform infrared (FT-IR) of fire residues demonstrated that P-C vibration between LDH-P and PP was generated by intercalating LDH-P with P3O105− anion. Compared with the LDH-C, the LDH-P promoted the formation of a more continuous and compact char layer during the burning process. Thus, the LDH-P intercalating with P3O105− anion enhanced the flame retardancy of PP matrix. Promising developments for use of LDH-P in flame retardant formulations were expected in future applications.