Thermal decomposition study of 1,4-diisobutyl-2,3,5,6-tetrahydroxy-1,4-diphosphorinane 1,4-dioxide

The thermal decomposition behavior of 1,4-diisobutyl-2,3,5,6-tetrahydroxy-1,4-diphosphorinane 1,4-dioxide (Cyagard), a fire retardant additive, was studied by thermogravimetry, differential scanning calorimetry, FT-IR and GUMS. Cyagard decomposes vigorously exhibiting a strong sharp-exothermic effect. This effect is caused by a phosphine oxide --> phosphinate --> phosphonate rearrangement. The created P-OC ester bonds further degrade to form acidic P-OH and ketone P-COCH3 bonds. The scission of the P-C bond yields acetaldehyde which evolves in the gas phase. In high boiling decomposition products, diphosphine dioxides, as well as species containing acidic P-OH and ester P-OC bonds are detected. (C) 2004 Elsevier B.V. All rights reserved.