Study On Flame Retardance Of Intumescent Flame Retarded Low Density Polyethylenes With Oxidants And Charring Agents

The main purpose of this thesis was aimed to strengthen char formation of intumescent flame retarded low density polyethylenes by adding oxidant and charring agent in order to improve the flame retardancy properties of LDPE blends. The flame retarded properties of intumescent flame retarded LDPE blends in the presence of oxidant ((NH₄)₂SO₄) and the charring agents (coal and asphalt) were studied with the limited oxygen index and the horizontal burning methods. The flame retardant, thermal and thermo-oxidative degradation mechanisms of flame retarded LDPE were investigated with thermal analysis techniques (DSC and TG). The relationship between the char layer morphology and the retardant efficiency was discussed based on the observation with scanning electron microscopy (SEM).The main important findings are as follows:(1) All additives improved properties of intumescent flame retarded LDPE blends to various extents, EVA enhanced the elongation at break and char formation. 2phr SiO₂ improved tensile strength at break, elongation at break and the impact strength of notched specimens. (NH₄)₂SO₄ oxidatively strengthened char formation, SiO₂ synergistically enlarged flame retardation with ammonium sulfate. 10-15 phr of (NH₄)₂SO₄ and 2 phr of SiO₂, together with 30 phr of intumescent flame retardant (IFR), could maximize the flame retardance of LDPE.(2) The values of limited oxygen index of flame retarded LDPE were increased and the bi-continuous interlocked phases were gradually formed with the increase of...