Effects of layered double hydroxides on the thermal and flame retardant properties of intumescent flame retardant high density polyethylene composites
Santosh Khanal, Yunhua Lu, Dandan Jin, Shiai Xu
Abstract
Summary In this study, two layered double hydroxides (LDHs), ZnAl‐LDH, and MgAl‐LDH, were combined with intumescent flame retardant (IFR) consisting of ammonium polyphosphate and tris (2‐hydroxyethyl) isocyanurate to prepare flame retardant high density polyethylene composites. The thermal and flame retardant properties of these composites were investigated by thermogravimetric analysis, limiting oxygen index measurement, and cone calorimetry, while the morphology and chemical structure of the char residue were analyzed by scanning electron microscopy, Fourier transfer infrared spectroscopy, and laser Raman spectroscopy. The results showed that the peak heat release rate (PHRR) of both HD/IFR/Zn‐LDH and HD/IFR/Mg‐LDH composites was 52.0% and 12.0% lower than that of HD and HD/IFR, respectively, suggesting that there was no difference in the reduction of PHRR between the two LDHs. The use of LDHs resulted in the formation of compact char residue with a high graphitic degree, but no significant increase in tensile strength.