Poly(L-Lactic Acid) Foaming With SC-CO₂: The Influence Of Homogeneous Nuclei On Foam Morphology

Abstract: In this technical paper, homogeneous crystal nuclei are exploited as heterogeneous nucleation sites for bubbles in poly (l-lactic acid) (PLLA) physical foaming to improve expansion ratios. PLLA slabs are thermally annealed to form homogeneous crystal nuclei and then foamed using super critical CO2 as physical blowing agent. Crystal population density and thermal properties of the polymer were studied before foaming and resulting foams were then observed via Scanning Electron Microscopy, and cell number density and average diameter were calculated. The density of homogeneous crystal nuclei influences foam morphology with the effect of increase cell density and reduce average cell diameter with the formation of smaller stamen-like cells surrounding growing spherulites.

Biography: Graduated in chemistry at University of Bari, Alessandra landed in Naples in 2018 as Research Fellow at National Research Council, studying the thermal properties of Poly(-lactic acid). Afterwards she started her PhD in Product and Process Engineering at FoamLab at University of Naples, focusing her research activity on the interaction between crystals and bubbles in physical foaming.

Exploiting her knowledge of crystallization mechanisms of PLA, Alessandra studies the influence of crystals and chain aggregates on foaming and she reached the goal of tuning foam morphology by simply vary the annealing time of the semi-crystalline polymer.