Phosphorus-Bromine Flame Retardant Synergy in a Polycarbonate/Polyethylene Terephthalate Blend

Abstract

The literature contains many claims to phosphorus/bromine flame retardant synergy. Many of these reports appear to be based upon a nonlinear response-concentration relationship. This paper shows convincing data for synergy in a a 2/1 polycarbonate/polyethylene terephthalate blend. The literature also shows phosphorus efficiency as a flame retardant to be 3-8 times more effective than bromine, depending on the polymer and flame retardant. These data show phosphorus to be about ten times more effective than bromine in a 2/1 polycarbonate/PET blend. Brominated phosphates, where both bromine and phosphorus are in the same molecule, were also studied. In one case synergy is further enhanced when both phosphorus and bromine are in the same molecule. On a weight basis, phosphorus and bromine in the same molecule are perhaps the most efficient flame retardant combination. KEY WORDS: flame retardants, phosphorus flame retardants, bromine flame retardants, synergy, phosphorus/bromine synergy, brominated phosphates, polycarbonate/polyethylene terephthalate blend, flame retarded engineering thermoplastics.

Development of Multifunctional Flame Retardants for Polymeric Materials

“…In particular, if compounds which would simultaneously promote char formation at the surface of the polymer and at the same time display effective gas-phase disruption of the flame propagating reactions could be found a significant advance in flame retardant technology might be possible. In fact, there is some evidence that such agents might display a synergy of action (i.e., that the effectiveness of either mode of action might be enhanced in the presence of the other) (4)(5)(6). This would mean that smaller amounts of total additive would be required to impart the desired level of flame retardancy.…”

Flame Retardants, Phosphorus

“…Nevertheless, combinations of phosphorus and halogens are often quite useful, and there are data supporting synergism with specific combinations and compounds (46,47). The strongest synergism has been found with certain compounds having bromine and phosphorus in the same molecule, such as tris(2,4-dibromophenyl) phosphate (48).…”

Structural Basis for Intumescence – Part III – Thermal Degradation Study of Intumescent Polymers Containing Spirophosphorus Moiety in the Backbone

“…Elemental red phosphorus [1][2][3] , water-soluble inorganic phosphates, insoluble ammonium polyphosphates [4][5][6] , organophosphates and phosphonates [7] , phosphine oxides [8][9][10] and chloro aliphatic and bromo aromatic phosphates [11][12][13][14] are the diverse phosphorus containing chemicals widely used in polymers as flame retardants. These chemicals having different chemical properties function differently in their flame-retardant mechanism [15][16][17] .…”