Thermal properties and fire behavior of polyethylene with a mixture of copper phosphate and melamine phosphate as a novel flame retardant

In this study mixture of copper phosphate and melamine phosphate (CUMP) was introduced into high-density polyethylene (HDPE) and examined. The thermal effects of the developed materials were analysed using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) as well as thermogravi-metric analysis (TGA). The reaction to fire of the HDPE with a developed flame retardant (FR) was determined by cone calorimetry (CC). The microstructure of the samples and char residues after the CC tests were assessed with a scaning electron microscope (SEM). Moreover, the analysis of volatile products evolved during the thermal degradation and burning was performed using TGA (TGA/FT-IR), as well as steady state tube furnace (Purser/FT-IR), both coupled with FT-IR. It was found that the presence of copper catalyzes the degradation process, which may have a beneficial impact on char formation. Degradation in lower temperature range allows shorter hydrocarbon chains to undergo the cyclization process forming more complex aromatic structures, which are significantly more thermally stable and contribute to the formation of the char layer. PE/CUMP formed more char compared to the PE as well as PE with comercial FR. However, some disadvantages regarding smoke emission, connected with long smoldering time, were observed.