The Influence of Typical Layered Inorganic Compounds on the Improved Thermal Stability and Fire Resistance Properties of Polystyrene Nanocomposites

Organic-modified montmorillonite (OMMT), organic-modified layered double hydroxide (SDS-LDH) and graphene (GNS) were three typical layered inorganic compounds. The polystyrene (PS) nanocomposites were prepared using in situ polymerization method. X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, and microscale combustion calorimeter were used to investigate the morphology and microstructure, thermal stability, and combustion performance of the PS nanocomposites. It was evident that the addition of the typical layered inorganic compounds could improve thermal stability and flame retardancy of PS. The results revealed that organic-modified layered double hydroxide and graphene were dispersed in PS matrix with mainly exfoliated structure, whereas OMMT distribution with intercalated and few exfoliated structure. The PS/OMMT nanocomposites exhibited superior flame retardance over PS/SDS-LDH and PS/GNS. Compared to pure PS, a 25% decrease in the peak heat release rate value was obtained for PS nanocomposites containing 3.0 wt% OMMT. The thermogravimetric analysis results demonstrated that the addition of OMMT led to the improvements in the thermal stability and char residues of the PS nanocomposites, especially the T_−50% and T_max of the PS/5.0 wt% OMMT nanocomposites had improved by 38°C and 63°C, respectively, compared to those of pure PS. The improvement of thermal stability and fire resistance properties was primarily attributed to the physical barrier effect of layered inorganic nanosheets and the catalytic carbonization behavior of layered double hydroxide.