Extrusion assisted by supercritical CO 2 : A review on its application to biopolymers

Extrusion assisted by supercritical CO2 (sc-CO2) is an emerging method for the microcellular foaming of polymer. Instead of batch foaming, which requires formation of single-phase polymer/CO2 solution in long cycle times, the extrusion assisted by supercritical fluids overcomes this issue by providing rapid mixing and dissolution of CO2 in the polymer melt. Because the sc-CO2 is soluble in many molten polymers and acts as a removable plasticizer, its introduction in an extruder will permit a decrease of the processing temperature. This technic allows the use of fragile component like active molecule or starchy and proteinaceous materials. At the end of the extruder, the pressure drop will create instability and phase separation with the creation of porosity. This review is dedicated to the extrusion assisted by sc-CO2 with different types of biopolymer. Industrial application domains include agro-food, biomedical, pharmaceutical, packaging and many others.