Recycled Poly(hydroxybutyrate-co-valerate) as Food Packaging: Effect of Multiple Melt Processing on Packaging Performance and Food Contact Suitability

This study examines the opportunity of using recycled poly(hydroxybutyrate-co-valerate) (PHBV) as food packaging. The recyclability was evaluated by assessing the effect of repeated polymer processing (up to four extrusion cycles) on the structural and barrier properties of the material, as well as its ability to produce neo-formed chemicals susceptible to migrate into food. It was shown that increasing the number of processing cycles results in a decrease of the polymer molecular weight, leading to a decrease of mechanical properties, balanced by a maintenance of the crystalline structure and of the thermal stability. The oxygen and water vapour transfer properties were also maintained after four cycles suggesting that r-PHBV-based packaging can retain its property and use panel. The specific migration of crotonic acid, one of the main products of the thermomechanical degradation of the PHBV was measured in three different food simulants. In all cases, it did not exceed the specific migration limit (SML) set at 0.05 mg/Kg food, revealing the food contact suitability of non-contaminated recycled PHBV under test conditions.