Functionalized nanodiamond as potential synergist in flame-retardant ethylene vinyl acetate

Pristine and phosphorylated detonation nanodiamonds (ND) were incorporated in ethylene vinyl acetate (EVA) as potential synergist agents to improve flame retardancy. Combinations of 5 wt% of pristine or modified ND and 20 or 25 wt% of Ammonium Polyphosphate (APP) were investigated using ThermoGravimetric Analysis (TGA), Pyrolysis Combustion Flow Calorimeter (PCFC), and Cone Calorimeter (CC). The study of thermal stability shows that APP and pure ND interacts, resulting in the formation of a char residue which is stable up to 750 degrees C. A strong reduction in the peak of HRR at Cone Calorimeter is highlighted for APP/ND combinations. PCFC data show that the peak of heat release rate (pHRR) decreases with the additive content. All these experiments suggest the formation of a thick charring layer, able to protect the material during thermal degradation. SEM micrographs confirm that EVA/APP/ND residues are more cohesive than EVA/APP ones.