Synthesis of aminopropyltriethoxysilane grafted/tripolyphosphate intercalated ZnAl LDHs and their performance in the flame retardancy and smoke suppression of polyurethane elastomer

A novel flame retardant containing both phosphorus and silicon elements, composed of aminopropyltriethoxysilane grafted/tripolyphosphate intercalated ZnAl LDHs (A-LDHs), was synthesized by anion exchange and IHS (induced hydrolysis silylation) method, and characterized by XRD, FTIR, XPS, and TG. After being added into a PUE matrix, A-LDHs could exfoliate and disperse randomly in the matrix while the composites containing pristine LDHs (N-LDHs) still preserved the stacking lamellar structure. Moreover, T5, T10, T50 and Tmax of the composites containing A-LDHs were higher than those of PUE/LDHs composites containing N-LDHs, resulting from the good dispersion of A-LDHs. And A-LDHs performed better in the flame retardancy and smoke suppression of PUE than N-LDHs. Furthermore, the mechanism was investigated through the analysis of the condensed phase after cone calorimetry tests via LRS, FTIR and XPS. The findings showed that the improved flame retardancy and smoke suppression might originate from a more stable char layer due to the introduction of P and Si elements.