Efficiency assessment of additives in thermal degradation of i-PP by chemiluminescence - I. Triazines

In this paper the kinetics of thermal oxidation of isotactic polypropylene with some new mercaptotriazines is presented. Isothermal degradation of i-P P was studied by chemiluminescence in air at 180 degrees C on polymer sampl es containing various concentrations of stabilizers (0.15. 0.25, 0.50 and 0 .75 wt%). The antioxidant efficiencies in thermal protection of i-PP were a ssessed by means of temporal parameters (t(i) t(1/2) and t(max)), oxidation rates (V-ox(max)), relative activities (A) and relative stabilities (S) re lative to a standard (Irganox 565). The concentration constants that charac terize the stabilization effect of triazinic antioxidants were calculated a nd linear correlation between OIT and sigma-Hammett constants could be poin ted out. (C) 2000 Elsevier Science Ltd. All rights reserved.