Supercritical CO2 assisted extrusion foaming of PLA- cellulose fibre composites: Effect of fibre on foam processing and morphology

This work is focused on the effect of the content and length of cellulose fibres on PLA foams produced by extrusion-foaming process assisted by sc-CO₂. The produced foamed samples were characterised by water pycnometry, modulated differential scanning calorimetry, and scanning electron microscopy. Increasing the length and the content of cellulose fibres results in a reduction of the expansion of the foams at a given die temperature. Nevertheless, long fibres at low content allows an increase of the longitudinal expansion of the foams. Furthermore, composite foams can be processed at a lower die temperature than neat PLA, providing a wider processing window. In general, the addition of cellulose fibres increases the crystallinity of the foams. Narrower cell size distributions and smaller cells are obtained when adding fibres, implying more homogeneous foam structures.