Moisture sensitivity and compressive performance of 3D-printed cellulose-biopolyester foam lattices

Abstract

Biobased, foam-like polyester composite materials were 3D-printed from a thermoset paste formulation. This paste formulation was composed of sebacic acid, glycerol, citric acid, and cellulose nanocrystals in water and ethanol with potassium chloride as a salt porogen. Thin walls and lattices were 3D-printed with geometry selected to facilitate post-printing processes such as water removal during polyester curing and the post-curing removal of the salt porogen. The compressive performance of these moisture-sensitive lattice structures was investigated after conditioning at different humidity levels and by water immersion. Finite element analysis was used to simulate the compressive performance of these porous lattice structures using a crushable foam material model. Addition of plant triglyceride oils from sunflower and coconut were trialled to modify the compressive performance and moisture sensitivity. Addition of 5 wt% coconut oil to the formulation prior to 3D-printing was found to lower the cured material's stiffness under dry conditions while increasing the compressive plateau strength of the lattice structures after water immersion.