Interplay Between Processing Phenomena and Molecular Structure in Poly(Lactic Acid)/Poly(Butylene Adipate-co-Terephthalate) Blend Foams

Poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blend foams containing 2, 4, and 6 phr chain extender (CE) were extruded at varying barrel and die temperatures (160, 175, and 190 °C). The correlations of the foams’ structural and physical properties with the rheological, molecular structure, and crystallization were investigated in depth. The analysis demonstrated that the foam with 2 phr CE extruded at 190 °C (FPPCE2T190) and the foam with 4 phr processed at 175 °C (FPPCE4T175) exhibited superior properties among the samples studied. Gel permeation chromatography revealed an enhancement in molecular weight for CE-containing foams, with the foam containing 4 phr CE prepared at 190 °C (FPPCE4T190) achieving a higher molecular weight than FPPCE4T175. Rheometric mechanical spectrometry identified that the FPPCE4T190 exhibited a highly branched structure with numerous short branches, while FPPCE4T175 featured fewer longer branches. Differential scanning calorimetry (DSC) further confirmed these findings, indicating that FPPCE4T190 achieved the highest degree of crystallinity. These results highlight the critical influence of CE content and processing temperature on the molecular structure and physical properties of the PLA/PBAT blend foams.