Synergistic effect of combining amino trimethylphosphonate calcium and expandable graphite on flame retardant and thermal stability of rigid polyurethane foam

Amino trimethylphosphonate calcium (Ca-ATMP) has been synthesized and applied to rigid polyurethane foam (RPUF). Synergistic effect of Ca-ATMP and expandable graphite (EG) on flame retardant and thermal stability of RPUFs has been investigated by using the limiting oxygen index (LOI) method, smoke toxicity analysis, Cone calorimeter analysis (CONE), and thermogravimetric analysis (TGA). The experimental results indicated that LOI of the RPUF was 26.3% when the ratio of Ca-ATMP and EG was 1:5. And the peak heat release rate (PHRR) of this proportion of RPUF decreased by 52.4% compared with that of RPUF without flame retardant. In addition, this modified RPUF possessed the maximum apparent activation energy (E) and produced the least toxic gas. On the basis the above data, it can be found that the synergistic effect of Ca-ATMP and EG on flame retardant and thermal stability of RPUFs has the most significant effect when the addition amount of Ca-ATMP and EG is 1:5, which is helpful for improving flame retardation of the RPUF.