Lever, T.J. (1982) A mechanistic study into the flame retardant and smoke supressant properties of molybdenum trioxide in brominated polyester thermosets. (PhD thesis), Kingston Polytechnic, .

Abstract

The use of molybdenum trioxide as a smoke suppressant and flame retardant in bromine-containing polyester;thermosets has been studied. Oxygen index studies showed that Mo0[sub]3 has a synergistic flame retardant effect when incorporated into the brominated polyester resins. During flaming combustion, polymers containing Mo0[sub]3 produced less smoke and more char. Thermogravimetric studies indicated that the inclusion of Mo0[sub]3 in the polymer affected its degradation profile. The Mo0[sub]3 was found to have no effect on the first of the three observed weight loss steps, which appeared to be due to the loss of phthalic anhydride from the resin. Changes were observed in the temperatures and weight losses of both of the subsequent degradation steps. Again it was found to increase the char levels and lower the temperature of char oxidation. No transfer of molybdenum to the vapour phase was-observed, no evidence being found for the formation of a volatile molybdenum halide on oxy-halide. MoO was recovered practically quantitatively after polymer degratlation in air, although in nitrogen it ended up as the carbide. Further evidence for the condensed phase mechanism was found in nitrous oxide index studies of the polyester where the index increased in the presence of Mo0[sub]3. Changes were observed in both the •condensed and vapour phase degradation prodccts in the presence of Mo0[sub]3' Elemental analysis of the solid residues rema1ning after heat1ng the polymer formulations showed that Mo0[sub]3 accelerated the loss of halogen to the vapour phase. This effect is thought to be responsible for the flame retardant activity of Mo0[sub]3• Inclusion of MoO into the polyesters resulted in a,change in the ratio of aromatic to aliphatic degradation products. Overall the quantity of aromatics evolved was reduced. Since these are the precursors of smoke in flaming combustion, their attenuation could account for the smoke redtction properties of Mo0[sub]3 in the presence of bromine.

Actions (Repository Editors)

Item Control Page