Two novel algorithms for the thermogravimetric assessment of polymer degradation under non-isothermal conditions

Abstract

Two novel algorithms are presented for processing thermogravimetric (TG) data obtained during the degradation of a polymer in a single step mechanism under non-isothermal conditions. The first algorithm assesses three characteristics computed from the TG profile against a theoretical data set, and identifies likely kinetic models to fit the experimental data. The second algorithm provides an iterative arithmetic method to extract the apparent activation energy, Ea, and Arrhenius A-factor, A, from TG data without simplifying assumptions. The algorithms are validated using model data and applied to data for the non-isothermal degradation of poly(ethylene adipate), poly(lactic acid) (PLA) and a food packaging PLA composite formulation containing kenaf, a natural fibre. The analysis of poly(ethylene adipate) produced Ea = 137 kJ mol−1 and log10A = 8.71 (first-order kinetic model). The kenaf fibre destabilizes PLA, lowering its Ea from 190 kJ mol−1 to 150 kJ mol−1 (contracting volume model).