PLA filament with pine cone flour: the Romanian study that turns forest waste into 3D printing material
A team of Romanian researchers has developed a composite filament that incorporates ground Scots pine cones into traditional PLA. The study, published in the journal Sustainability, demonstrates that a small percentage of forest biomass produces superior mechanical results compared to higher loads.
From forest to extruder: the transformation process
Researchers at Ștefan cel Mare University of Suceava have turned waste pine cones into fine flour, mixing it with PLA to produce 1.75 mm filament compatible with desktop FFF printers.
The team led by Irina Beșliu-Băncescu, Florin Ursachi, and Gelu-Marius Rotaru collected Pinus sylvestris pine cones in the Suceava region, in northeastern Romania. The cones were dried, ground, and sieved to obtain particles between 125 and 180 micrometers.
Particle size represents a critical compromise. Particles that are too large cause irregularities in the filament and can block the printer nozzle. The chosen fraction allows maintaining a true lignocellulosic component while remaining compatible with desktop FFF systems.
Filament production process
- Biomass preparation: Drying and grinding of pine cones, sieving between 125-180 μm.
- Mixing: Combination of vegetable flour with PLA in percentages of 5% or 10% by weight.
- Extrusion: Production of 1.75 mm filament through a single-screw extruder.
- Print test: Creation of test specimens on Creality Ender 3 V2 with 0.2 mm layer at 25 mm/s.
5% beats 10%: less biomass means more strength
Against intuitive expectations, the filament with lower pine cone flour load showed superior mechanical performance in all main tests.
The filament with 5% flour reached an average tensile strength of 21.06 MPa, compared to 18.51 MPa for the 10% version. The elongation at break was also higher: 7.35% versus 4.69%.
The researchers attribute this behavior to the nature of untreated biomass. Pine cone flour acts more as a filler than as a reinforcement. Plant fibers attract moisture, while PLA is relatively hydrophobic: this incompatibility probably creates microvoids around the particles, generating weak points when the material is subjected to tension.
| Parameter | Filament 5% | Filament 10% |
|---|---|---|
| Tensile strength | 21.06 MPa | 18.51 MPa |
| Elongation at break | 7,35% | 4,69% |
| Post-print strength | ~18 MPa (85%) | ~14.5 MPa (79%) |
Attempting to exceed the 10% load produced thicker material, difficult to handle, with a tendency to agglomerate and clog the nozzle. There is therefore a practical limit to the amount of biomass that the process can handle.
From printing to characterization: the limits of the FFF process
The printing process further reduced the mechanical properties, as typically happens when a continuous filament becomes an object composed of deposited layers.
The printed specimens with the 5% formulation reached about 18 MPa, those with 10% about 14.5 MPa. This means a retention of 85% and 79% respectively of the original filament strength.
The printed samples appeared slightly more extensible than the raw filament. The researchers, however, urge caution in interpreting this data: the strain measurements came from the testing machine and not from optical extensometers, and only three printed specimens were tested for each formulation.
The authors describe the results on the elongation of the printed samples as preliminary, given the limited sample size and the measurement method used.
Prospects for biocomposites in additive manufacturing
The study confirms the technical feasibility of incorporating forest waste into FFF filament, but also highlights the limitations of untreated natural fillers.
The research fits into an increasingly active field: using underutilized biological residues as a component of new filaments, reducing the amount of virgin polymer needed. The Romanian approach favors simplicity: no complex chemical treatment of the biomass before mixing with PLA.
This represents an advantage in terms of cost and process complexity. At the same time, the absence of surface treatments on the plant particles limits the interfacial adhesion between the phases, compromising the final mechanical properties.
- The filament with 5% pine flour outperforms the one with 10% in strength and elongation
- Loads higher than 10% cause workability problems and nozzle clogging
- Untreated biomass acts as a filler, not as a structural reinforcement
- The printing process reduces mechanical properties by 15-21% compared to the filament
The publication in Sustainability on August 27 documents a pragmatic approach to the valorization of forest waste. The results suggest that for structural applications, surface treatments of particles or compatibilizers will be necessary. For less demanding applications, the 5% material could already represent a sustainable alternative to pure PLA.
article written with the help of artificial intelligence systems
Q&A
Which pine nut flour percentage offers the best mechanical performance?
The filament with 5% pine nut flour showed superior performance compared to the 10% version. Tensile strength reached 21.06 MPa versus 18.51 MPa for the higher load.
What is the ideal particle size for the pine nut flour used in the study?
Researchers selected particles between 125 and 180 micrometers after drying and sieving. This size prevents nozzle clogging while maintaining compatibility with desktop FFF printers.
Why does a lower biomass load produce better mechanical results?
Pine nut flour acts as a filler, and incompatibility with hydrophobic PLA creates micro-voids around particles. A lower load reduces these weak points, improving strength and elongation at break.
Which 3D printer was used to test the new composite filament?
Printing tests were conducted using a Creality Ender 3 V2. Specimens were produced with a layer height of 0.2 mm and a printing speed of 25 mm/s.
From which plant species does the biomass used for the filament originate?
The study used cones from Pinus sylvestris (Scots pine) collected in the Suceava region of Romania. These forestry wastes were processed into fine flour to be blended with PLA.
