Waste wool/polycaprolactone filament towards sustainable use in 3D printing

Abstract

3D printing is a popular technique for numerous applications from households to industrial purposes. Commercially available filaments for 3D printing are not eco-friendly, yet energy intensive due to their high extrusion temperature (200–220°C). Polycaprolactone (PCL) is increasingly proposed for 3D printing due to its biocompatibility and lower extrusion temperature, which is more sustainable, though is slow in actual biodegradation. Although PCL-blends are often proposed to promote the degradation, strong hydrophobicity of PCL leads to poor compatibility. This study, for the first time proposes waste wool/PCL filaments for 3D printing using a clean production method, to utilise the hydrophobicity of wool as an advantage with PCL interfaces. Micro-sized wool powders from waste wool fabrics of two fibre fineness (16 and 24 μm) were prepared with minimal in-process waste and then extruded completely with PCL using different ratios (10/90, 20/80 and 25/75 combination of wool/PCL) to produce the composite filaments. A uniform mixing in the composite structure was observed particularly with 10% of wool loading, also the biodegradation rate significantly increased, i.e., from 0.8% to 6.8–10.5% in 3 months. Filaments prepared with 10% and 20% wool showed an increased yield strength, while a finer diameter of initial fibre was found more influential in changing tensile, thermal, and crystalline properties. The reduction in crystallinity was found correlated to the increasing amount of wool, though interlayer spacing of PCL was unaltered and overall thermal stability improved. The filaments were found printable through a 0.4 mm nozzle using a desktop 3D printer at 80 mm/min speed. The findings suggested the possible use of the produced filaments for fabrication of varied products, such as containers for holding or packing, toys, and other common household objects or industrial tools.