Tuning pore size and density of rigid polylactic acid foams through thermally induced phase separation and optimization using response surface methodology

Rigid polylactic acid (PLA) foams fabricated via thermally induced phase separation (TIPS) utilizing a ternary solution of PLA, Tetrahydrofuran (THF), and water. The PLA gels were stabilized mechanically by the substituting of the THF/water solvent mixture with ethanol as non-solvent and subsequently vacuum dried. A comprehensive characterization of PLA foams was achieved by Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD) and Brunauer-Emmett-Teller (BET) analyses. The BET area obtained in the PLA foam is up to 18.76 m2/g. The Response Surface Methodology (RSM) was utilized to assess the impacts of four independent variables (polymer concentration, solvent composition, quench temperature, and aging time) on the pore size and density of PLA foam. The experimental findings demonstrated that the fabrication parameters could be fine-tuned to govern the morphology of the pores, comprising their size and density. The optimal values of parameters for cell size were identified by RSM to be 8.96 (wt%), 91.60 (w/w), 5.50 °C, and 3.86 h for the optimum cell size of 37.96 µm (37.78 by Genetic Algorithm). Optimum density by RSM 88.88 mgr/cm3 (88.38 mgr/cm3 by Genetic Algorithm) was obtained at 5.00 (wt%), 89.33 (w/w), 14.40 °C and 2.65 h.