The kinetic models analyses of hydrogenated natural rubber during non-isothermal degradation process

Hydrogenated natural rubber (HNR) was prepared by diimide reduction of natural rubber (NR) latex and characterized by FT-IR, H-1 NMR and TG-DTG. The thermal degradation kinetic models of HNR were studied under a nitrogen atmosphere by TG-DTG. Achar and Coats-Redfern methods were used to study the non-isothermal kinetics models change during the thermal degradation process of NR after hydrogenation. The results indicated that HNR with 34.69% and 63.74% hydrogenation degree were prepared. A one-stage pyrolysis pathway could be observed from all the TGA curves which were shifted to higher degradation temperatures with the rise of saturation degree. The similar activation energies obtained by both Coats-Redfern and Achar methods confirmed that the kinetics calculation was accurate. The results showed the best-fit models of the samples with the highest regression coefficient values (R-2 > 0.90) were chemical reaction models. The reaction order was three (N3) in NR case and the corresponding mechanism functions were g(alpha) = [(1-alpha)(-2)-1]/2, f(alpha) = (1-alpha)(3). The reaction order was two (N2) when it came to HNR with hydrogenation degree of 34.69%. The most probable mechanism functions were g(alpha) = (1-alpha)(-1)-1, f(alpha) = (1-alpha)(2). As the degree of hydrogenation increased to 63.74%, the reaction order best-fit changed to one (N1) which was proved to be the same as the ethylene-propylene diene rubber samples. And the mechanism functions were g(alpha) = -ln(1-alpha), f(alpha) = 1-alpha. The thermal degradation models of polymers was closely related to the structure. And the structure effects affected the degradation behavior as well as the thermal properties of polymers.