AbstractIn the 2‐furaldehyde based polymer investigated by ESR, at 300 K 4. 1018spins/g with g = 2.00306have been observed (presumably carbon centered polyenyl radicals). The kinetic description of the radical concentration at 320 to 470 K implies three steps; (i) a sudden jump found to be partially reversible with temperature, (ii) gradual growth, and (iii) radical decay (proportional to partial pressure of oxygen). The kinetic parameters of the individual reaction steps have been evaluate