Characterisation of natural fibre reinforced PLA foams prepared by supercritical CO2 assisted extrusion

Abstract

Abstract. Natural fibre reinforced polylactic acid (PLA) foams, as potential green replacements for petroleum-based polymer foams, were investigated. Highly porous (ε > 95%) microcellular PLA foams were manufactured by supercritical CO 2 assisted extrusion process. To overcome the inherently low melt strength of PLA, epoxy-functionalized chain extender was applied, while talc was added to improve its crystallization kinetics. The combined application of chain extender and talc effectively promoted the formation of uniform cell structures. The effect of cellulose and basalt fibre reinforcement on the foamability, morphology, structure and mechanical properties of the PLA foams were investigated as well. The addition of 5 wt% natural fibres promoted the cell nucleation, but caused non-uniform distribution of cell size due to the microholes induced by local fibre-matrix debonding. The compression strength of the manufactured basalt fibre reinforced PLA foams reached 40 kPa.

Mastering the structure of PLA foams made with extrusion assisted by supercritical CO2

“…with w CO 2 the mass fraction of CO 2 , q H2O p the solid polymer density, and q amb CO2 the CO 2 density at room pressure and temperature being 1.78 3 10 23 g cm 23 (Nist table 34 ). This calculation is made with the assumption of no CO 2 escape from the sample.…”

“…Nofar showed that well‐dispersed nanoparticles (micro‐sized talc, nanosilica, and nanoclay) enhanced the expansion ratio and cell density of the foamed samples, thanks to a large number of induced crystals through the nanoparticles. Extrusion foaming of PLA has also been implemented in blend with poly(butylene adipate‐ co ‐terephthalate) (PBAT), another biodegradable polymer, or with natural fibres, and the effect of temperature on final properties has been studied. In the case of wood‐flour addition, authors have observed the effect of the melt flow index (MFI) on the foam properties.…”

“…It has been shown that with decreasing die temperature, porosity and expansion ratio increased. 13,14,16,17,20,22,23 The effect of sc-CO 2 content on the foam density has been mainly investigated. [10][11][12][13] It has been shown that the CO 2 content has to be above 7 wt % for giving highly expanded foams.…”

Preparation of Low-Density Microcellular Foams from Recycled PET Modified by Solid State Polymerization and Chain Extension

“…On one hand, they break the homogeneity of the polymer melt, and the created heterogeneous system favors the diffusion and dispersion of the foaming gas, and on the other hand, increase the number of crystal-nuclei formed [30]. Importance of the latter role lies in the stabilization of the cell structure that becomes easier with increasing crystallinity, therefore a mechanically more stable structure can be achieved [31]. The most important parameters of nucleating agents of porous mineral types are their particle size and surface characteristics.…”

Foamability and viscosity behavior of extrusion foamed PLA–pulp fiber biocomposites

“…The study concluded that cellulose fibers acted as nucleating agent for PLA in foaming, improving the cell morphology. In addition, Bocz et al . showed that addition of 5 wt % of cellulose fibers promoted cell nucleation, but also led to less uniform cell structure and increased open cell ratio due to weak fiber matrix adhesion and fiber dispersion.…”