Moisture Sorption Isotherms and Thermodynamic Properties of Biodegradable Polymers for Application in Food Packaging Industry

Abstract

This work aims to evaluate the influence of two starch-based materials (B16 and B20) on the moisture sorption isotherms, determined at 30, 40, and 50 °C, where B16 contains 5% (w/w) more starch than B20. Thermodynamic functions (differential enthalpy (∆Hdif), differential entropy (∆Sdif), integral enthalpy (Δhint), integral entropy (ΔSint), free Gibbs energy (∆G), and spreading pressure (φ)) were used to understand the water-binding behaviors and the energy requirements to remove the moisture content from the surface of these materials. The moisture sorption isotherms exhibited type III behavior, and the Guggenheim–Anderson–de Boer (GAB) model was the most suitable to fit the experimental moisture adsorption data. The adsorption isotherms of microparticles were enthalpy-controlled, with isokinetic temperature values of 221.45 and 279.77 K for B16 and B20, respectively, being higher than the harmonic mean temperature (312.94 K). The values of ∆G were positive (45.274 and 44.307 kJmol−1 for B16 and B20, respectively), indicating a non-spontaneous process. The spreading pressure values increased with increasing water activity (aw) for all isotherms. Higher values of ∆Hdif and ∆Sdif obtained from B16 confirmed its higher number of sorption sites available for binding with water molecules when compared to B20, making it less suitable for application in the food packaging industry.

Effect of Incorporation of Graphene Nanoplatelets on Physicochemical, Thermal, Rheological, and Mechanical Properties of Biobased and Biodegradable Blends

“…B20, a starch-based polymer containing polybutylene adipate-co-terephthalate (PBAT), was produced using a twin-screw extruder with a melt flow index (MFI) of 4.6 g/10 min (130 • C, 10 kg) and a density of 1.28 g/cm 3 [32]. Polybutylene succinate (PBS) with an MFI of 18 g/10 min (190 • C, 2.16 kg) and a density of 1.25 g/cm 3 was provided by Xinjiang Blue Ridge Tunhe Polyester Co., Ltd. (Changji City, China).…”

Obtaining and Characterizing New Types of Materials Based on Low-Density Polyethylene and Thermoplastic Starch

“…Nevertheless, TPS has multiple advantages: it is completely biodegradable, is non-toxic, has a low cost, is obtained from renewable sources, and does not affect the environment [5][6][7]. TPS cannot be used as such for various industrial applications due to its inadequate mechanical and chemical properties (like fragility or water sensitivity) [8] or low thermal stability [9]. The hydrophilic nature of TPS [10] and moisture-induced 2 of 18 recrystallization (retrogradation) usually lead to an increase in rigidity and separation of the polymer/solvent phases [11,12].…”