Green Composites Based on Mater-Bi® and Solanum lycopersicum Plant Waste for 3D Printing Applications

Abstract

3D printability of green composites is currently experiencing a boost in importance and interest, envisaging a way to valorise agricultural waste, in order to obtain affordable fillers for the preparation of biodegradable polymer-based composites with reduced cost and environmental impact, without undermining processability and mechanical performance. In this work, an innovative green composite was prepared by combining a starch-based biodegradable polymer (Mater-Bi^®, MB) and a filler obtained from the lignocellulosic waste coming from Solanum lycopersicum (i.e., tomato plant) harvesting. Different processing parameters and different filler amounts were investigated, and the obtained samples were subjected to rheological, morphological, and mechanical characterizations. Regarding the adopted filler amounts, processability was found to be good, with adequate dispersion of the filler in the matrix. Mechanical performance was satisfactory, and it was found that this is significantly affected by specific process parameters such as the raster angle. The mechanical properties were compared to those predictable from the Halpin-Tsai model, finding that the prepared systems exceed the expected values.

Keywords: 3D printing; FDM; biopolymers; green composites; solanum lycopersicum.

Figure 1

SEM images of SL powder.

Figure 2

SEM images of MB/SL5, MB/SL10 and MB/SL15 filaments.

Figure 3

Rheological curves of MB/SL5, MB/SL10 and MB/SL15 filaments.

Figure 4

Tensile properties of MB/SL5, MB/SL10 and MB/SL15 filaments as a function of the SL amount.

Figure 5

Photos of MB/SL5, MB/SL10 and MB/SL15 filaments before (a–c, respectively), during (d–f, respectively) and after (g–i, respectively) tensile test.

Figure 6

Different behaviours of the filament upon entering the melting chamber, at different viscoelastic and mechanical properties.

Figure 7

SEM images of fracture surfaces of MB/SL10 0° samples at increasing magnification (from left to right). The green circle highlights the good adhesion between the matrix and the filler.

Figure 8

SEM images of tensile fracture surfaces of MB/SL5 0° samples. The pink circles highlight fibre pull-out and debonding phenomena.

Figure 9

SEM image of tensile fracture surface of MB/SL5 ± 45° sample.

Figure 10

SEM image of tensile fracture surface of MB/SL10 0° sample.

Figure 11

SEM images of tensile fracture surfaces of MB/SL10 ± 45° samples. The blue circles and arrows highlight fibre pull-out and debonding phenomena.

Figure 12

Elastic modulus (E), tensile strength (TS) and elongation at break (EB) of 3D-printed samples as a function of the filler content; raster angle = 0° (left) and raster angle = 45° (right).

Figure 13

Elastic modulus (E), tensile strength (TS) and elongation at break (EB) of 3D-printed samples with different filler content and raster angle.

Figure 14

XRD spectra (a) and DSC analysis (b) of neat MB and MB/SL−printed composites.

Figure 15

Ratio between elastic modulus of the composite and the polymer matrix, as a function of the SL content, according to the Halpin–Tsai model (HT) and the experimental results (Exp).