Effects of coal and ammonium polyphosphate on thermal degradation and flame retardancy of polyethylene terephthalate

Abstract

Polyethylene terephthalate (PET) is of excellent mechanical properties and melt processability and is widely used as raw material for textile fibers and engineering plastics. However, its flame retardant properties are rather poor, and its melt-dripping behavior during burning hasn’t been handled properly. In this work, coal powder and ammonium polyphosphate (APP) were blended with PET, and the thermal degradation, flame retardancy, char formation and mechanical properties of the modified PETs were investigated. All results show that, the initial thermal degradation was accelerated remarkably with APP but to less extent with coal. The gasification of carbonaceous residues was suppressed by the two additives at higher addition levels. The oxygen indice of the modified PETs with APP were increased whereas unchanged with coal unexpectedly. APP/Coal synergistically improved the flame retardancy of PET. There existed some physical and chemical interactions among PET, APP and coal during combustion process. The mechanical properties of the modified PETs were worse than those of virgin PET.