The thermooxidative degradation of methyl methacry late-graft-natura l rubber(MG) in air was studied by Thermogravimetric Analysis(TGA). The results indicate that the thermooxidative degradation of MG-30 in air has one weight lo ss step change on the whole. The degradation temperatures and the degradation ra tes increase linearly along with the increment of heating rates. The temperature of initial degradation ( t 0) is 0 667 B +351 7 ℃, the temperature at maximum deg radation rate ( t p) is 0 923+385 4 ℃, and the temperature of final degra dation ( t f) is 0 923+385 4 ℃. The degradation rate at t p is not affected by B and its a verage value is 46 7%. However, the degradation rate at t f gains linearly with the increase of B and its average value is 93 0%.
