Effect of pressurized CO2 and N2 on the rheology of PLA

[Display omitted] •PLA viscosity during assisted melt-extrusion processing was successfully evaluated.•PFAs are more effective to plasticize PLA than conventional bio-based ATBC.•Addition of 1.7 wt% CO2 allows reducing 10 °C the processing temperature.•N2 produces the highest plasticization effect, but the processing window is narrow.•PFAs produce additive-free porous extrudates, while processing at lower temperatures. Melt-polymer processing is conventionally employed for thermoplastic polymeric materials. The rheological behaviour of the polymer is then of critical importance to correctly accomplish the process. The effect of pressurized fluid additives (PFA), such as CO2 and N2, has been investigated in this work to determine the extension of their beneficial plasticization effect on PLA. In-line measurements performed by a custom-designed slit-die rheometer were conducted at different temperatures and PFA concentrations, and the viscosity values of PLA/PFA mixtures were experimentally determined and compared to those obtained when adding a commercial plasticizer, acetyltributylcitrate (ATBC), to PLA. Our results suggested that a twofold reduction of PLA viscosity is achievable using addition of 2.65 wt% pressurized CO2 respect to similar contents of ATBC. Furthermore, a decrease of 10 °C of the processing temperature could be attained when adding 1.70 wt% of CO2. This work aims at shedding light on the rheological behaviour that PLA experiences during assisted-melt extrusion processing, and on how more favourable energetic processing could be achieved by lowering temperature, if the appropriate type and concentration of PFA is employed during processing.