Investigation of thermal stability and flammability of poly(methyl methacrylate) composites by combination of APP with ZrO2, sepiolite or MMT

The thermal degradation and flame retardancy of poly(methyl methacrylate) containing three mineral fillers, with different geometry, MMT: plate-like, sepiolite: fibrilar and zirconium oxide ZrO2: spherical, in combination with ammonium polyphosphate (APP) were studied. The flame behavior of composites was investigated using pyrolysis-combustion flow calorimeter, cone calorimeter and LOI tests. The results revealed that the composites containing APP and sepiolite present the best fire behavior. A rheological study was performed on composites to establish a relationship between viscosity and flammability. The residues of samples after cone calorimeter test were studied using X-ray diffraction and micro-tomography in order to investigate their chemical composition and also repartition of fillers. A better repartition of sepiolite during combustion could be the origin of the best results obtained for sample containing this filler.