Poly(butylene succinate) and poly(butylene succinate-co-adipate) for food packaging applications: Gas barrier properties after stressed treatments

Aliphatic polyester resins present the versatility of common plastics and are characterized by a good stability under ordinary conditions. They have acquired significant interest as environmentally friendly thermoplastics for a wide range of application, like food packaging field. We have investigated the permeability behavior of commercial poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA) polymers after food contact simulants and photo and thermal-oxidative degradation processes. Each stressed treatment was applied on thin film. Barrier properties to different gases (oxygen and carbon dioxide) were evaluated, showing that the chemical composition of the polymer strongly influenced the permeability to the gasses. Further, the same samples were tested at different temperatures, from 5 °C to 40 °C, in order to understand the effect of the temperature on the permeability behavior, and to calculate the process activation energy. Relations that bind the diffusion coefficients (D) and solubility (S) with temperature were studied. Differential Scanning Calorimetry (DSC) and FT-IR analyses were carried out in order to establish a correlation between permeability and sample structure/crystallinity. Negligible changes were evidenced in the polymers by means of DSC and FTIR measurements indicating structural stability of the polymers under process conditions. Gas barrier behavior, instead, resulted mainly affected by the process conditions, because mainly dependent on several chemical-physical factors. In both cases, no severe damage of the materials was observed.