The thermal behavior, mechanism and kinetic parameters of the exothermic decomposition reaction of lead salts of 2-hydroxy-3,5-dinitropyridine (2HDNPPb) and 4-hydroxy-3,5-dinitropyridine (4HDNPPb) in a temperature-programmed mode have been investigated by means of DSC, TG-DTG and lower rate thermolysis/FT-IR.Their reaction mechanisms were proposed.Their critical temperatures of thermal explosion were calculated.The catalytic effects of 2HDNPPb and 4HDNPPb on the composite modified double base (RDX-CMDB) propellant containing RDX were studied.The results show that the apparent activation energy and pre-exponential constant of the major exothermic decomposition reaction of 2HDNPPb and 4HDNPPb, at 0.1 MPa, are 252.34 kJ·mol^-1 and 10^19.30 s^-1, 187.39 kJ·mol^-1 and 10^13.74 s^-1, respectively.The critical temperatures of thermal explosion of 2HDNPPb and 4HDNPPb obtained from the onset temperature (T_e) and the peak temperature (T_p) are 327.64℃ and 336.57℃, 323.90℃ and 333.96℃, respectively.The thermal stability of 2HDNPPb is better than that of 4HDNPPb.Their kinetic equations of the major exothermic decomposition process at 0.1 MPa can be expressed as:
for 2HDNPPb dα/dT=10^20.48(1-α)^3/5e^-3.0351×104/T
for 4HDNPPb dα/dT=10^15.00(1-α)^2/3e^-2.2539×104/T
2HDNPPb and 4HDNPPb possess better catalytic effect and ability to reduce pressure exponent for RDX-CMDB propellant.In comparison with 4HDNPPb, 2HDNPPb has the higher catalytic efficiency.The positions of the hydroxyl group in the molecules were the principal factor affecting the thermal stability and the catalysis activity of 2HDNPPb and 4HDNPPb.

Key words: lead salt of 2-hydroxy-3,5-dinitropyridine, lead salt of 42hydroxy-3,5-dinitropyridine, thermal decomposition, mechanism, kinetic parameter, composite modified double base propellant containing RDX, catalysis