Degradation kinetics and lifetime prediction for polystyrene/nanocellulose nanocomposites
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Degradation kinetics and lifetime prediction for polystyrene/ nanocellulose nanocomposites Roberta Motta Neves1 · Heitor Luiz Ornaghi Jr.2 · Felipe Gustavo Ornaghi2 · Sandro Campos Amico3 · Ademir José Zattera1 Received: 2 April 2020 / Accepted: 28 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
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. Keywords Nanocellulose · Polystyrene · Nanocomposites · Thermal behavior · Kinetics · Lifetime prediction
Introduction Nanocomposites reinforced with cellulose have recently attracted attention due to their potentially high mechanical and thermal properties, low density and, biodegradability characteristics. Nanocellulose (NC) is usually extracted from wood or vegetal fibers using different methods and classified based on their dimensions and chemical characteristics as nanofibers (CNF) [1, 2], nanocrystals (CNC) [3] or bacterial * Roberta Motta Neves [email protected] 1
Postgraduate Program in Engineering of Processes and Technologies (PGEPROTEC), Universidade Caxias do Sul (UCS), Rua Francisco Getúlio Vargas, 1130, Caxias do Sul 95070‑560, RS, Brazil
2
Fatigue and Aeronautical Material Research Group, Department of Materials and Technology, School of Engineering, Universidade Estadual Paulista (UNESP), Av. Dr. Ariberto Pereira da Cunha, 333, Guaratinguetá 12516‑410, SP, Brazil
3
Postgraduate Program in Mining, Metallurgical and Materials Engineering (PPGE3M), Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil
nanocellulose [4]. CNC is sometimes incorporated into polymeric thermoplastics as polystyrene (PS). PS is used in a range of applications such as food packaging and shelf life [5, 6], thermal insulators in buildings, and biomaterial for cell culture [7], and it has been used with nanocellulose in order to improve mechanical or dynamic–mechanical properties [8] and thermal properties [9, 10]. For the
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