Films from bio-based aliphatic/aromatic poly(trimethylene furanoate/sebacate) random copolymers for smart sustainable food packaging: gas permeability properties under different conditions of use and after contact with food simulant fluids

Abstract

Films from bio-based poly(trimethylene 2,5-furandicarboxylate-co-trimethylene sebacate) (PTFcoPTSeb) random copolymers were deeply characterized from the gas permeability point of view in order to evaluate their possible use for food packaging under different conditions of temperature and humidity. From previous studies of the same authors, such films appeared very promising, showing smart gas permeability properties under standard testing conditions (23 °C) to oxygen (O₂) and carbon dioxide (CO₂), the primary gases of interest in food packaging applications. In detail, in the present paper, the influence of temperature on gas permeability was assessed at 5 °C, 15 °C, and 38 °C, with the lowest value mimicking refrigeration conditions and the highest value the temperature of tropical countries. Furthermore, the films were subjected to food simulant exposure, specifically 10% v/v ethanol (to mimic fatty foods) and 3% w/v acetic acid (to represent aqueous foods). Last but not least, to evaluate the impact of humidity, the samples were conditioned in two distinct relative humidity (RH) environments: a temperate climate (23 °C, 85% RH, using saturated KCl) and a tropical climate (38 °C, 90% RH, using saturated KNO₃). The films after contact with food simulants were analyzed with respect to gas permeability performance, thermal behavior, mechanical properties, and optical characteristics (including color and transparency). Comparative analysis with untreated films revealed a strong correlation between the copolymer composition, treatment conditions, and resultant performance. While each treatment exhibited a distinct influence depending on the chemical structure of the material, all copolymers demonstrated excellent permeability properties against O₂ and CO₂. Among the investigated materials, the copolymer containing 15 mol% PTSeb exhibited the most balanced performance under dry conditions, while showing limitations under high humidity conditions. Thermal analysis confirmed the chemical stability of the copolymer films post-treatment, and mechanical testing indicated the preservation of their structural integrity. The films remained transparent, exhibiting a slight yellowing, which intensified marginally according to the various treatments.