Dual-exterior surface modification of layered double hydroxides and its application in flame retardant biobased poly(trimethylene terephthalate)

The overall target of this research was to design a dual-exterior surface chemical modification of eco-friendly layered double hydroxides (LDH-S@PA) using calcium stearate and phytic acid (PA) containing-rich phosphorus to synchronously boost the dispersibility in the polymer matrix and the flame retardancy. Microstructure, surface chemical environments and morphologies of LDH-S@PA were characterized. It was found that the target product with the hydrophobic surface was successfully prepared. The basic morphologies of LDH-S@PA exhibited thin flat crystals composed of multi-sheet with hexagonally arranged spots. Meanwhile, the thermal stability of LDH-S@PA was improved. Significantly, after adding LDH-S@PA into biobased poly(trimethylene terephthalate) (PTT) via melting-blending, LDH-S@PA exhibited a higher dispersity in the PTT matrix and the PTT/LDH-S@PA composite with 20 wt% loading achieved 29.8% limiting oxygen index value and possessed V-0 rating in UL-94 test, revealing LDH-S@PA dramatically enhanced the flame retardancy of the PTT. The flame retarded mechanism of LDH-S@PA in PTT was discussed based on gaseous and condensed phase analysis. In addition, the incorporation of LDH-S@PA improved the mechanical properties of the composites. This facile and straightforward approach for dual-surface modification LDHs holds promise as flame retardant formulations for polymer in future applications.