Co-authors​ :

 Laura ALIOTTA (ITALY), Claudia SERGI (ITALY), Bianca DAL PONT , Maria-Beatrice COLTELLI , Vito GIGANTE (ITALY), Andrea LAZZERI  

The use of fillers from agricultural waste to obtain bio composites, has been widely adopted in literature essentially to reduce the materials costs. Recently, the attention has been paid to circular economy where one of its principles is the waste valorisation. In this context, the addition of agriculture waste to produce new biocomposites formulations to be used in different application field, attracted much interest. Recently, thanks to the advent of additive manufacturing (AM) techniques, new bio composites formulations containing wastes by-products have been explored by Fused Deposition Modeling (FDM) technique. In this work the valorisation of hazelnuts shells has been investigated. The hazelnuts shells grinding leads to hazelnut shell powder (HSP) that can be easily compounded with a thermoplastic matrix in a twin screw-extruder. In this work different amount of HSP (from 10 up to 30 wt.%) were added in a poly(lactic acid) (PLA) matrix in a semi-industrial twin-screw extruder to obtain new PLA/HSP formulations to be used by FDM 3D printer for design applications (like jewellery and home accessories) exploiting the natural aesthetic colour of the HSP. In fact, the addition of HSP provides to the final bio composites a natural woody effect that can be exploited to produce 3D printed customized objects. A Tumaker NX Pro pellets 3D printer was used that starts the printing direct from pellets allowing to bypass the filament production step and to reduce the costs. Once that the best HSP content was selected, to improve the final density and the mechanical performance of the material, the optimization of the printing speed and temperature nozzle was carried out by the Design of Experiment (DoE) approach. The FDM manufactured bio composites were mechanically characterized (by flexural, tensile and impact tests) and the results compared with the same bio composites obtained by classical injection molding technique. It was noticed that, for the formulation containing 10% wt. of HSP, the mechanical properties of injection moulded, and 3D printed specimens were very similar. On the contrary, by using pure PLA the properties of the 3D printed specimens were significantly lower than the injection moulded ones, suggesting that 3D printing from pellets represents an effective valorisation of these bio composites. The specimen’s roughness was also measured to identify the best 3D printing configuration in terms of surface finishing. The effect of three different raster angles (0, 90 and ± 45°) on the final mechanical properties was also analysed and to conclude, 3D printed jewelleries (in real dimension) and home furniture (in scale) were produced as “validated objects”.