Degradation kinetics and lifetime prediction for polystyrene/nanocellulose nanocomposites

Abstract

Cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs) were incorporated into polystyrene (PS), and thermal stability and lifetime prediction of the nanocomposites were investigated for variable filler content (0.25, 0.50 and 1% w/w). Thermogravimetric analysis (TG) was carried out at four different heating rates (5, 10, 20 and 40 °C min−1) in a non-isothermal condition, and the degradation kinetics was studied based on Friedman and Flynn–Wall–Ozawa (FWO) methods. The same thermal degradation behavior was observed for all samples in the studied range of reinforcement content. For both reinforcements (CNFs and CNCs), Friedman and FWO results showed no dependence of the activation energy on conversion degree. A single-step degradation mechanism was observed for all samples (A → B degradation model), and the kinetic studies indicated an autocatalytic reaction model with a good fitting of the curves. Lifetime prediction based on kinetic analysis was successfully applied. Lastly, nanocellulose morphology influenced nanocomposite lifetime prediction, which became more stable over time, maintaining almost 100% of the mass for 10 years exposed at 30–120 °C.