Valorization of Tomato Stem Waste: Biochar as a Filler in Three-Dimensional Printed PLA Composites
Abstract
1. Introduction
2. Materials and Methods
2.1. Materials
2.2. Production of Biochar from Tomato Stem Waste
2.2.1. Grinding of Tomato Stem Waste
2.2.2. Biochar Production via Slow Pyrolysis of Tomato Stem Powder
2.3. Production of PLA/Biochar Composite Filaments
2.4. Additive Manufacturing Process (Specimens with Rectilinear and Concentric Patterns)
2.5. Characterization and Testing
2.5.1. Elemental Analysis
2.5.2. Dynamic Light Scattering (DLS)
2.5.3. N2 Physisorption
2.5.4. Thermal Gravimetric Analysis (TGA)
2.5.5. FTIR Spectroscopy
2.5.6. Scanning Electron Microscopy (SEM)
2.5.7. Differential Scanning Calorimetry (DSC)
2.5.8. Mechanical Properties
2.5.9. Dynamic Mechanical Analysis (DMA)
3. Results
3.1. Biochar Characterization
3.2. PLA/Biochar Composites Properties
3.2.1. Morphological and Structural Characterization
3.2.2. Thermal Transitions
3.2.3. Mechanical and Thermomechanical Properties
4. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Abbreviations
3D | Three dimensional |
AM | Additive Manufacturing |
ANOVA | Analysis of Variance |
ASTM | American Society for Testing and Materials |
BET | Brunauer–Emmett–Teller |
DLS | Dynamic Light Scattering |
DMA | Dynamic Mechanical Analysis |
DSC | Differential Scanning Calorimetry |
FDM | Fused Deposition Modeling |
FFF | Fused Filament Fabrication |
PBS | Poly(Butylene Succinate) |
PLA | Poly(Lactic Acid) |
PSD | Particle Size Distribution |
SEM | Scanning Electron Microscopy |
SLS | Selective Laser Sintering |
TGA | Thermal Gravimetric Analysis |
TSP | Tomato Stem Powder |
UV | Ultraviolet |
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Filament Type | Components | ||
---|---|---|---|
PLA | Biochar | Joncryl | |
(wt.%) | (wt.%) | (wt.%) | |
Neat PLA | 98 | - | 2 |
PLA-5% Biochar | 93 | 5 | 2 |
PLA-7.5% Biochar | 90.5 | 7.5 | 2 |
Type of Test | Specimen Morphology | Infill Pattern | Number of Specimens | ||
---|---|---|---|---|---|
Neat PLA | PLA-5% Biochar | PLA-7.5% Biochar | |||
Tensile Strength | ASTM D638 Standard, Type V | Concentric/ Rectilinear | 5/5 | 5/5 | 5/5 |
Flexural Strength | rectangular parallelepiped 50 × 5 × 2 mm | Concentric/ Rectilinear | 5/5 | 5/5 | 5/5 |
Dynamic Mechanical Analysis | rectangular parallelepiped 50 × 5 × 2 mm | Concentric/ Rectilinear | 5/5 | 5/5 | 5/5 |
Elemental Analysis | DLS | N2 Physisorption | |||
---|---|---|---|---|---|
C (wt.%) | 61.93 | Particle diameter (μm) | 2.2 | BET surface area, SBET (m2/g) | 2.048 |
H (wt.%) | 2.38 | Hydrodynamic diameter (μm) | 2.0 | ||
N (wt.%) | 2.21 | Pore volume, VP (cc/g) | 0.015 | ||
O (wt.%) | 33.48 |
Temperature Range | Tonset | TDTO max | Tend | Mass Loss |
---|---|---|---|---|
(°C) | (°C) | (°C) | (°C) | (%) |
24–220 | 24.3 | 81.6 | 132.4 | 4.65 |
220–520 | 403.6 | 472.8 | 514.3 | 9.18 |
520–760 | 637.0 | 684.0 | 752.8 | 9.86 |
Sample | 1st Heating | 2nd Heating | ||||||
---|---|---|---|---|---|---|---|---|
Tc | Tcc | Tm | Xc | Tc | Tcc | Tm | Xc | |
(°C) | (°C) | (°C) | (%) | (°C) | (°C) | (°C) | (%) | |
Neat PLA | 63 | 127 | 152 | 0.16 | 61.7 | 128 | 152.3 | 0 |
PLA-5% Biochar | 66.7 | 121.7 | 150.7 | 0 | 62.7 | 125.7 | 151.4 | 0 |
PLA-7.5% Biochar | 65.6 | 118.74 | 150.4 | 0 | 61.6 | 123.7 | 151.1 | 0 |
Property | Neat PLA | PLA-5% Biochar | PLA-7.5% Biochar | |||
---|---|---|---|---|---|---|
Concentric | Rectilinear | Concentric | Rectilinear | Concentric | Rectilinear | |
Tensile Testing | ||||||
Tensile strength, σb (MPa) | 41.5 ± 9.2 | 46.8 ± 12.8 | 32.9 ± 0.6 | 32.0 ± 0.2 | 33.4 ± 0.8 | 30.3 ± 0.8 |
Elongation at break, εb (%) | 3.3 ± 0.3 | 4.6 ± 1.0 | 2.9 ± 0.1 | 2.9 ± 0.1 | 3.3 ± 0.1 | 3.0 ± 0.0 |
Young’s modulus, Eb (MPa) | 1347 ± 155 | 1149 ± 175 | 1286 ± 2 | 1242 ± 8 | 1212 ± 19 | 1123 ± 19 |
Flexural Testing | ||||||
Flexural strength, σf (MPa) | 52.3 ± 3.9 | 38.5 ± 2.6 | 72.9 ± 1.3 | 71.7 ± 4.0 | 68.9 ± 4.7 | 60.0 ± 3.7 |
Flexural strain at break, εf (%) | 0.17 ± 0.03 | 0.13 ± 0.04 | 0.17 ± 0.01 | 0.20 ± 0.02 | 0.20 ± 0.03 | 0.20 ± 0.07 |
Modulus of elasticity, Ef (MPa) | 984.0 ± 59.3 | 657.8 ± 56.7 | 772.2 ± 223.3 | 540.1 ± 69.7 | 520.7 ± 31.4 | 492.2 ± 66.4 |
Dynamic Mechanical Analysis | ||||||
Storage modulus, E’, at 30 °C (MPa) | 1298 | 1228 | 1385 | 1310 | 1183 | 1145 |
Storage modulus, E’, at 65 °C (MPa) | 147 | 148 | 95 | 119 | 117 | 104 |
Glass transition temperature, Tg (°C) | 59.3 | 59.8 | 59.5 | 60.4 | 57.4 | 59.2 |
Additive Type | Typical Additives | Mechanical Impact | Thermal Stability | Printability |
---|---|---|---|---|
Biochar [21,61,69,70,91] | Biochar from different sources at 5–40 wt.% loadings | Mechanical reinforcement at low (5–10 wt.%) loadings; mechanical properties decrease in higher (>10 wt.%) loadings | Minor changes in thermal stability, glass transition temperature, and degree of crystallinity | Potential increase in agglomeration, extrusion torque, and nozzle abrasion; moisture sensitivity |
Natural fibers [42,76,79,83,87,89] | Wood powder, natural fibers, etc. | Moderate increase in stiffness; reduced tensile strength | Minor improvement in heat deflection | Increased nozzle wear; moisture sensitivity |
Synthetic fibers [73,74,77,78,80,84,90,92] | Carbon fibers, glass fibers, Kevlar, etc. | Significant gain in tensile strength and stiffness | Substantial increase in glass transition | Higher extrusion torque; nozzle clogging risk |
Inorganic particles [67,75,81,82,88,94,95,96] | Calcium carbonate, talc, metal oxides, etc. | Improved dimensional stability; slight stiffness gain | Enhanced dimensional accuracy | Better melt flow; reduced shrinkage |
Nanomaterials [68,71,72,85,86,93] | Graphene, carbon nanotubes, etc. | Exceptional rise in strength and modulus | Considerable increase in thermal stability | Requires controlled dispersion; potential nozzle abrasion |
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Gkiliopoulos, D.; Pemas, S.; Torofias, S.; Triantafyllidis, K.; Bikiaris, D.N.; Terzopoulou, Z.; Pechlivani, E.M. Valorization of Tomato Stem Waste: Biochar as a Filler in Three-Dimensional Printed PLA Composites. Polymers 2025, 17, 2565. https://doi.org/10.3390/polym17192565
Gkiliopoulos D, Pemas S, Torofias S, Triantafyllidis K, Bikiaris DN, Terzopoulou Z, Pechlivani EM. Valorization of Tomato Stem Waste: Biochar as a Filler in Three-Dimensional Printed PLA Composites. Polymers. 2025; 17(19):2565. https://doi.org/10.3390/polym17192565
Chicago/Turabian StyleGkiliopoulos, Dimitrios, Sotirios Pemas, Stylianos Torofias, Konstantinos Triantafyllidis, Dimitrios N. Bikiaris, Zoi Terzopoulou, and Eleftheria Maria Pechlivani. 2025. "Valorization of Tomato Stem Waste: Biochar as a Filler in Three-Dimensional Printed PLA Composites" Polymers 17, no. 19: 2565. https://doi.org/10.3390/polym17192565
APA StyleGkiliopoulos, D., Pemas, S., Torofias, S., Triantafyllidis, K., Bikiaris, D. N., Terzopoulou, Z., & Pechlivani, E. M. (2025). Valorization of Tomato Stem Waste: Biochar as a Filler in Three-Dimensional Printed PLA Composites. Polymers, 17(19), 2565. https://doi.org/10.3390/polym17192565