Flame-Retarded High Density Polyethylene with an Intumescent Flame Retardant Synthesized in a Phosphorus-Containing Solvent

An intumescent flame retardant (IFR), melamine salt of pentaerythritol phosphate (MPPL) was successfully synthesized in a phosphors-containing solvent, triphenyl phosphate (TPP). This novel method had the advantages as follows: (1) TPP melt served as an organic solvent effectively dissolving and dispersing the reactants, melamine phosphate (MP) and pentaerythritol (PEL), at the reaction temperature; (2) when cooled to the room temperature after the reaction, TPP transited from melt into solid and involved in the synthesized MPPL. Without additional purification like conventional chemical reactions using organic solvents, the involved TPP could play the role of a synergist with MPPL to effectively improve the flame retardance. The molecular structure of the MPPL synthesized was confirmed by series characterization. Flame retardance measurements showed obvious enhancement for MPPL containing TPP flame-retardant high density polyethylene (HDPE) compared with a purified MPPL system. The flame-retarded processes and synergistic mechanisms were investigated and described.