Upcycling Macadamia Nut Shells: The effect of Particle Size and Moisture Content on 3D printed Nutshell-Plastic Composites

Abstract

This paper investigates the effects of particle size and moisture content on the structure and material properties of extruded composite filaments composed of macadamia nutshell (MN) flour and acrylonitrile butadiene styrene (ABS), using Scanning Electron Microscopy (SEM). The moisture content of the MN flour was reduced to 7.05% by a three-hour drying process. The size of the particles of MN flour in the composites was varied by using different sieves; despite the size variation, a morphology study of the particles shows that the shape of the particles remains similar for each size range.  The SEM micrographs show that large voids were introduced into the sample during the extrusion process to create the filaments, with larger but less frequent voids occurring in the dried samples. The micrographs also show the samples were homogenously mixed by using the single screw extruder. The paper also examines how the optimization of printing variables were used leading to a superior sample