Flame retardancy and smoke suppression of silicone foams with modified microencapsulated Mg/Zn/Al-layered double hydroxide

Silicone foams (SiFs) are high-performance materials but can combust and release choking smoke in a fire. In this paper, the modified microencapsulated Mg/Zn/Al-layered double hydroxide (MLDHs) was prepared by the sol-gel method. Then, the structure and performance of modified MLDHs were characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TG), and differential scanning calorimetry (DSC). Besides, the mechanical properties, flame retardancy, smoke suppression, thermal degradation behavior, morphology and composition of carbon slag of SiFs with modified MLDHs were tested using the universal tensile testing machine, limiting oxygen index (LOI), UL-94 test, cone calorimeter, thermogravimetry, SEM-EDS and XPS. The results indicated that the modified MLDHs could effectively improve the ductility of SiFs. When the addition of modified MLDHs exceeded 20 mass%, SiFs could be improved to UL-94-V0 rating. The PHRR, THR, and TSP of SiFs with 30 mass% modified MLDHs were 56.04%, 46.86%, and 80.49% lower than that of pure SiFs. Furthermore, the decomposition products of modified MLDHs/SiFs composite such as SiO2 and zinc magnesium aluminum oxide could improve the char formation significantly. The continuous, complete, and dense structure of carbon slag of modified MLDHs/SiFs could effectively block the exchange of heat and gas on the surface of SiFs and reduce the combustion performance of SiFs.

Automated summary

In this study, modified microencapsulated Mg/Zn/Al-layered double hydroxide (MLDHs) was prepared and characterized for improving the performance of silicone foams (SiFs). Various tests were conducted to evaluate the mechanical properties, flame retardancy, smoke suppression, thermal degradation behavior, morphology, and composition of SiFs with modified MLDHs. The results showed that the addition of modified MLDHs could effectively enhance the ductility and fire safety of SiFs by reducing heat release rate, total heat release, and smoke production.