3D Printing Filament Research Articles

Experimental and multiscale analysis of volume fraction effects in tensile properties of recycled PLA-PDA/kenaf fiber 3D printing filament composites

Polylactic acid, a biodegradable thermoplastic derived from renewable sources, has notable environmental advantages and versatile properties. However, recycled PLA often experiences reduced mechanical strength and altered chemical composition due to the recycling process, limiting its suitability for 3D printing filament applications. Recognizing the inherent limitations of recycled PLA (rPLA), this research employs a unique method of coating rPLA with dopamine (DA) and reinforcing it with kenaf fibers (KF) at various weight fractions, introducing a novel multiscale modeling approach to address the challenges of interfacial bonding and tensile performance in recycled polymers. The methodology integrates experimental single filament tensile testing with multiscale finite element modeling to accurately predict the composite’s mechanical behavior across different scales. The findings reveal that a 5% kenaf fiber weight/volume fraction provides the optimal balance between tensile strength, stiffness, and toughness, achieving a significant 49.3% improvement over the unreinforced rPLA. However, increasing the kenaf fiber content beyond 5% leads to a decline in mechanical properties, attributed to higher fiber agglomeration and suboptimal fiber-matrix interactions. The novelty of this research lies in its combined use of PDA coating, natural kenaf fiber reinforcement, and advanced multiscale modeling to enhance and predict the performance of rPLA-PDA/kenaf composites, paving the way for sustainable, high-performance materials in 3D printing applications.

Stabilizer Effects on the Gelation of Modified Recycled PET for 3D Printing Filament Application

This research identification gel types of the modified-recycled poly (ethylene terephthalate) (modified-rPET) filament, with and without the addition of heat stabilizer Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (Irganox®1010). This research also identifies the gel types and studies thermal behavior of the modified-rPET filaments above, by using a hot-stage microscopy, and a differential scanning calorimetry, respectively. rPET flakes were dried to deplete the moisture. Then, they were mixed with additives and heat stabilizer (Irganox®1010) at 0 and 0.5 pph, Then, they were extruded to be compound using twin screw extruder. The compounds were extruded into filament by using filament extruder. The two temperature profiles were used. The first and the second temperature profiles from the feed zone to the die zone were 275-275-275 oC and 290-290-290 oC, respectively. The extrudate of modified-rPET with and without heat stabilizer, were investigated the type of gel and the thermal behavior of the modified-rPET filament. From this preliminary experiment, it was found that the “unmelt-gel” defect was found from the modified-rPET filament, without the addition of Irganox®1010. On the other hand, the “crosslinked gel” defect was found from the modified-rPET filament, with the addition of Irganox®1010. Therefore, the addition of heat stabilizer (Irganox®1010) may cause the “crosslinked gel” significantly. Our future work, we will investigate the effect of another stabilizer and chain extenders on the gelation behavior, to complete this clarification systematically.

Modification of chain extension and crosslinking structures of recycled polyester textile for 3D printing filament

AbstractThe increase in amount of polyester textile waste is contributing to the severity of environmental pollution because polyester cannot be easily recycled. To reduce the limits of its recyclability, a value‐added recycling approach should be explored. This work introduces an approach for recycling polyester textiles into 3D printable filaments. To increase recyclability of polyester textiles, the polyester materials are modified by ADR4468 additive. After the polyester is 3D printed, the sample with 1.0 wt% of ADR4468 shows the highest tensile and compressive strength properties compared with 1.5 and 2.0 wt%, owing to its fewer voids between the printed lines, a fish scale‐like morphology that spreads out, and a higher degree of crystallization. Moreover, the mechanism of modification suggests that ADR4468 extends and crosslinks the polyester chains by ring‐opening reactions of epoxy groups of ADR4468 and forms sea‐island structures. The sea‐island structures of bonded polyester branched cores with tangled polyester shell interface areas and unbonded polyester chain areas performed suitable rheological behaviors to recycle polyester textiles for 3D printable filaments production. The filaments can be used to replace commercially available filaments, offer a sustainable option for consumers, and impact both the polyester textile‐related recycling and 3D printing industries.Highlights An approach is proposed to recycle polyester textiles for 3D printing filament The approach uses a mechanical method to recycle polyester textiles Recycled polyesters were modified by ADR4468 to form core‐shell structures Core‐shell structures were separated by short polyesters(sea‐island structure) The structures met rheological behaviors for 3D printing filament

Novel Softwood Lignin Esters as Advanced Filler to PLA for 3D Printing.

In this study, we explored the selectivity of softwood lignin toward esterification through chloromethylation. Organosolv pine lignin chloromethylated by a novel greener protocol was subjected to esterification with decanoic acid (C10), tetradecanoic acid (C14), and stearic acid (C18). The success of lignin esterification was confirmed by using FTIR and NMR spectroscopy. For composite preparation, modified lignin was incorporated with PLA in varying proportions (10%, 20%, 30%, and 40%) using the solvent casting technique. The thermal and mechanical properties of the solvent-cast films were analyzed. Notably, lignin esters increased the glass transition temperature (T g) of PLA by a few degrees: tetradecanoic acid (C14) at 30% loading exhibited increases T g from approximately 68 to 72 °C. Mechanical testing showed that blending PLA with lignin and its ester derivatives improves its properties. Pure PLA has moderated ductility and stress but lowered stress levels compared to PLA-lignin ester blends. Adding 30% lignin reduced strength and strain, making the material more brittle. In contrast, the PLA + lignin C14 ester (30%) blend achieved the highest stress and strain, enhancing toughness and strength. This makes lignin C14 ester a promising additive for improving the mechanical properties of PLA in applications requiring greater strength and toughness. The composition with optimum properties was selected for production of the 3D-printing filament. Three extrusion temperatures were evaluated, and the advanced mechanical properties of 3D-printed filament along with surface morphology were analyzed.

Comparative study of blending techniques in polylactic acid/cellulose nanofibrils green composites for benchtop 3D printing filaments

AbstractAdditive manufacturing for polylactic acid (PLA) reinforced with cellulose nanofibrils (CNF) could unlock fabrication of specialized and user‐specific biomedical devices. However, the process of combining PLA and CNF is challenging and proves complicated with possible irreversible CNF agglomeration and organic solvents leftover, particularly when involving solvent‐casting technique. Direct melt‐blending can mitigate these issues, but there are few reports of a single‐step melting and extrusion process to produce ready‐to‐use 3D printing filaments. This study compares the distribution of CNF fillers within the PLA matrix in PLA/CNF composites made by direct melt‐blending into filaments using a benchtop filament maker, and by solvent‐casting followed by extrusion into filaments. The filaments were 3D‐printed via fused deposition modeling (FDM), followed by tensile testing, morphology, and other characterizations. Uneven filament diameters were observed for the composite filaments prepared via solvent‐casting because of severe agglomeration, resulted in poor printability and tensile properties of filaments and 3D‐printed samples. Direct melt‐blended filament diameters were consistent, resulted in only slight decrease of tensile properties compared to pure PLA, contributing to the highest maximum tensile strength of 3D‐printed sample of 51.47 ± 1.73 MPa at 5% CNF loading. Morphology revealed good integration of CNF into PLA matrix starting at 3% CNF loading. Direct melt‐blending was comparable to the conventional methods, which enables simpler PLA/CNF composite preparation especially for 3D printing.Highlights Better dispersibility achieved by direct melt‐blending than by solvent‐casting. PLA/CNF filaments produced via solvent‐casting suffered severe agglomeration. Direct melt‐blended PLA/CNF5% yielded the highest maximum tensile strength. Morphology reveals good CNF‐PLA integration starting at 3% of CNF loading. Worsened agglomeration causing increased number of voids observed at 10% CNF.

Filaments for 3D Printing of Iridescent Structural Colors

Filaments for 3D Printing of Iridescent Structural Colors

Recyclable hemp hurd fibre-reinforced PLA composites for 3D printing

In this study, 3D printing filaments were produced from hemp hurd fibre-reinforced polylactide (PLA) composites. Hemp hurd microfibres were obtained through alkaline digestion followed by a bleaching treatment and were used to produce PLA-based composites with 20–40 wt% fibre content for fused deposition modelling. Tensile testing of 3D printed composites revealed a gradual increase of Young's modulus with the addition of fibres, reaching a maximum of 7.1 GPa for the 40 wt% composite - a two-fold increase to neat PLA. However, tensile strength was only improved for the 20 wt% formulation, with an increase of 8% in comparison with neat PLA. Nevertheless, the thermo-mechanical properties of the composites were significantly enhanced with the addition of fibres. In addition, physical objects were printed from the recycled filaments to assess their recyclability and printability. It was found that the recycled filaments maintained comparable mechanical properties and printability after three recycling cycles.

Decentralized approach for incorporating waste wind turbine blades into 3D printing filaments using mechanical recycling

AbstractThe increasing awareness in environmental safety has led to rapid development in production of electricity using wind energy with wind turbines. The widespread deployment of wind turbines has outpaced the effective recycling of End‐of‐Life wind turbines. This study explores the potential of mechanically recycling decommissioned wind turbine blades (WTB) as reinforcement material in 3D printing processes. Utilizing mechanical grinding, materials were extracted from the waste blades and subsequently analyzed using Fourier transform infrared spectroscopy, Differential scanning calorimetry, and thermogravimetric analysis to determine optimal processing conditions. The reclaimed materials were then blended with recycled polypropylene through single‐screw extrusion to fabricate tensile test samples via Fused Deposition Modeling. The impact of print orientation on mechanical strength was examined at 0°, 45°, and 90° angles. Morphological analysis was conducted on the fractured specimens to assess the failure characteristics. The findings indicate that samples printed at a 90° orientation exhibited superior mechanical properties, suggesting a viable pathway for incorporating wind turbine waste into sustainable manufacturing cycles.Highlights A decentralized‐mechanical recycling technique to the waste WTB. The necessary material parameters for the operations employed in this study. Reinforced 3D printable filaments from waste WTB. Stronger reinforced filaments obtained from proper fiber alignment.

Preparation and 3D printing parameters of thermo/electrically shape memory PLA/SEBS-g-MA/CB composites

In this work, novel thermo-responsive shape memory blends PLA/SEBS-g-MA and electro-responsive PLA/SEBS-g-MA/carbon black (CB) composites were prepared by melt blending, and were extruded into filaments for 3D printing. SEM images illustrate that the blends possess co-continuous structure at SEBS-g-MA ratio of 30 wt% and showcase remarkable shape memory properties (Rf 100%, Rr 85.3%), which were attributed to effective stress transfer. In the second part, PLA/SEBS-g-MA/CB composites were produced with different amounts of CB nanoparticles. The volume resistivity of composites with CB additions of 13 phr and above is maintained at about 102 Ω.cm, and the printed samples showed superior electro-responsive performance, with response completed in about 40 s at 60 volts DC. In addition, the effect of printing parameters on the mechanical properties was investigated and it was found that the choice of layer thickness was strongly related to tensile and flexural strength.

Melting and solution mixing in the production of photocatalytic filaments for 3D printing

3D printing is a fast-growing technology with benefits like rapid prototyping and versatile design capabilities. However, Fused Deposition Modeling (FDM) needs improvement due to limited material options. This study proposes a method for producing photocatalytic prototypes using 3D printing/FDM, focusing on environmental applications like contaminant degradation. Key steps included filament production through melt and solution mixing, defining geometries, 3D printing functional prototypes, and characterizing materials chemically, thermally, microscopically, and mechanically. The photocatalytic capacity was evaluated via tetracycline degradation, showing 45–60% efficiency for ZnO filaments and up to 65% for TiO2 filaments. ZnO-functionalized parts maintained 80% removal capacity after 10 reuse cycles without activation, indicating reduced leaching and photo corrosion. This study advances 3D printing/FDM research for environmental applications, providing a methodology for producing effective photocatalytic prototypes.

3D Printing Conductive Filament for Fuel Cell Bipolar Plates

Fuel cell bipolar plates are commonly manufactured from metals and graphite. Utilizing a polymer material, while still adhering to the standards set by the U.S. Department of Energy for bipolar plate electrical conductivity, could greatly reduce production costs and time. 3D printing bipolar plates could have benefits that include weight reductions as well as ease of testing different flowfield designs. However, very few 3D printing filaments are electrically conductive. In this work, samples were printed with Electrifi conductive filament, a copper-polyester composite material. Samples were printed at various conditions to determine optimal print settings for dimensional accuracy and electrical conductivity. Printing parameters such as nozzle temperature, flow rate, and infill pattern were varied to affect sample density and conductivity. Several combinations of print conditions led to conductivities nearing the US DOE technical target for bipolar plate conductivity. SEM imaging was performed to better understand the structure of the Electrifi filament, and an Energy-dispersive X-ray spectroscopy scan provided details on its elemental composition.

Mechanical Evaluation of Recycled PETG Filament for 3D Printing

Additive manufacturing (AM) is revolutionizing various industries by enabling the creation of complex structures with minimal waste. In the context of a circular economy, the importance of recycling cannot be overstated, as it plays a crucial role in reducing environmental impact and conserving resources. This study investigates the mechanical behavior of PETG in the context of recycling for 3D printing applications. With plastic waste posing significant environmental challenges, the pursuit of sustainable solutions is paramount. PETG has emerged as a promising material in additive manufacturing due to its favorable properties, but its sustainability remains a concern. Through mechanical testing, including tensile, compression, and impact tests, PETG specimens are evaluated after one cycle of recycling and reutilization.

Experimental studies on mechanical properties of metal fused filament fabricated SS316L

Fused filament fabrication is a simple and commercially popular additive manufacturing (AM) technique for developing high-accuracy polymer-based materials. In this experiment, a retrofit type of setup was developed to manufacture stainless steel 316L–based products. The current study focuses on the encapsulation of stainless steel with polylactic acid to prepare the filament for 3D printing. The effects of printing parameters such as layer thickness, infill density, and extruder temperature on responses like density, surface roughness, micro-hardness, and material/filament consumption have been studied. A Box–Behnken design approach was employed to systematically evaluate 15 specimens under varying conditions. The results revealed that a maximum relative density of 97% was achieved with a layer thickness of 0.2 mm, an extruder temperature of 215°C, and a 100% infill density. Additionally, the optimized infill density demonstrated a significant effect on both hardness and surface roughness, confirming the importance of precise control over processing conditions for improving the performance of the printed parts. The findings contribute to the advancement of metal-polymer composite filaments in additive manufacturing, highlighting their potential for producing complex, high-performance components.

Optimization of Glass-Powder-Reinforced Recycled High-Density Polyethylene (rHDPE) Filament for Additive Manufacturing: Transforming Bottle Caps into Sound-Absorbing Material.

Additive manufacturing presents promising potential as a sustainable processing technology, notably through integrating post-consumer recycled polymers into production. This study investigated the recycling of high-density polyethylene (rHDPE) into 3D printing filament, achieved by the following optimal extrusion parameters: 180 °C temperature, 7 rpm speed, and 10% glass powder addition. The properties of the developed rHDPE filament were compared with those of commonly used FDM filaments such as acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) to benchmark the performance of rHDPE against well-established materials in the 3D printing industry, providing a practical perspective for potential users. The resulting filament boasted an average tensile strength of 25.52 MPa, slightly exceeding ABS (25.41 MPa) and comparable to PLA (28.55 MPa). Despite diameter fluctuations, the filament proved usable in 3D printing. Mechanical tests compared the rHPDE filament 3D printed objects with ABS and PLA, showing lower strength but exceptional ductility and flexibility, along with superior sound absorption. A life cycle analysis underscored the sustainability advantages of rHDPE, reducing environmental impact compared to conventional disposal methods. While rHDPE falls behind in mechanical strength against virgin filaments, its unique attributes and sustainability position it as a valuable option for 3D printing, showcasing recycled materials' potential in sustainable innovation.

3D Printable Materials Based on Renewable Polymers from Terpene Alcohols and Calcium Carbide

AbstractThe transition to a sustainable future requires the use of waste‐free technologies for production. Potentially, additive technologies can be a promising approach for accessing circular economy due to the precise amount of feeding materials and the absence of molds. However, the initial feeding materials for additive approaches are often based on non–renewable hydrocarbon sources. This work focused on the use of polymers derived from terpene alcohols to develop a filament suitable for 3D printing. Initially, the vinylation of menthol using calcium carbide was optimized and scaled up, then a series of terpenyl–based vinyl ethers were obtained under optimal conditions. The cationic polymerization of vinyl ethers was also scaled up and resulted in 99 % yield of the polymers, which was subsequently subjected to hot extrusion. The initial terpenol was used as an additive to increase polymer flexibility. The addition of menthol (30 wt %) to polyvinyl menthol led to the suitable filament. Using the filament, a series of objects were 3D printed at 125 °C. The material demonstrated good sinterability and adhesion to glass and shrinkage comparable to that of commercial 3D printing filaments. Furthermore, the polymers obtained were used as additives to enhance the adhesion of commercially available filaments.

Multi-walled carbon nanotube-enhanced polyurethane composite materials and the application in high-performance 3D printed flexible strain sensors

Flexile strain sensors hold vast potential for applications in monitoring human motion, enabling human-machine interaction, and facilitating information transfer, etc. However, the available materials and manufacturing techniques for fabricating flexible strain sensors with high sensitivity and extended sensing range still face significant challenges. By utilizing solution casting and twin-screw extrusion techniques, this study prepared high-performance thermoplastic polyurethane/multi-walled carbon nanotube (TPU/MWCNT) nanocomposite 3D printable filaments, and employed material extrusion 3D printing technology to facilely fabricate flexible strain sensors. The 1-pyrene carboxylic acid (PCA)-modified TPU/MWCNT(3 wt%) nanocomposite exhibited outstanding mechanical properties, with a tensile strength of 24.3 ± 0.5 MPa and a fracture elongation of 625.8 ± 12.3 %. The 3D printed TPU/MWCNT(3 wt%)/PCA flexible strain sensors demonstrated amazing sensitivity (GFmax = 10279.95) within a wide strain range (0–300 % strain). The addition of PCA brings the benefits of improved dispersion of MWCNTs in the TPU composite, as well as enhanced thermal stability, and upgraded mechanical and electrical properties under different tensile strains. Meanwhile, the 3D printed samples displayed remarkable durability and reproducibility. Finally, the flexible strain sensors fabricated from this nanocomposite material could accurately perceive human motion, providing great prospects for wearable device applications.

Sustainable polymer reclamation: recycling poly(ethylene terephthalate) glycol (PETG) for 3D printing applications

Due to their versatile properties and wide-ranging applications across various industries, including manufacturing, polymers are indispensable for today’s society. However, polymer-based products significantly impact the environment since many are single-used plastics and require a long time to degrade naturally. A method to attenuate end-of-life polymers’ ill effects is recycling them to bring them again into the production cycle, from grave to cradle. This investigation involves recycling PETG sheets used in face shield production during the COVID-19 outbreak to fabricate 3D printing filaments for FFF. We assessed poly(ethylene terephthalate) glycol (PETG) processability to up to five recycling cycles and obtained filaments with properties adequate for 3D printing. Rheological, thermal, morphological, and mechanical characterization were analyzed to verify the effect of the number of processing cycles on the properties of the polymer. The recycling cycles originated a decrease in viscosity and elasticity, and the gain in molecular mobility resulted, relatively, in solids with a higher degree of crystallinity and prints with more elliptical depositions. The mechanical properties of printed parts fabricated of recycled material were comparable to those from commercial filament, especially after three extrusion cycles. Both extrusion and additive manufacturing processes successfully recycle material into filaments and printed parts, indicating that the proposed methodology is a promising alternative to bring value back to polymers from solid waste.

Advanced ternary carbon-based hybrid nanocomposites for electromagnetic functional behavior in additive manufacturing

This study explores the processing and performance of acrylonitrile butadiene styrene (ABS)-based carbon ternary hybrid nanocomposites, incorporating carbon nanotubes (CNT), graphene nanoplatelets (GNP), and carbon black (CB), for applications in electromagnetic compatibility (EMC). The effect of nanocomposite processing on electromagnetic properties was evaluated by varying the mixing protocol, either through direct extrusion with simultaneous addition of all constituents or by preparing a master batch followed by dilution. The impact of nanofiller morphology and processing techniques on the behavior of nanocomposites was systematically investigated. Filaments of these nanocomposites were Additive Manufactured via Material Extrusion, and the resulting parts were evaluated for EMI shielding effectiveness (SE) in the X-band frequency range. The study reveals that the morphology, influenced by the processing strategy, significantly impacts the EMI SE properties of the printed samples. Particularly, ternary hybrids 3/3/3 wt% (CNT/GNP/CB) nanocomposites demonstrate promising electrical (0.003 S/cm), electromagnetic (29 dB of total attenuation), and mechanical performance (elastic modulus of 3080 MPa), with a clear advantage observed in those processed via direct extrusion. These nanocomposites were validated as feedstock filaments for 3D printing, and the printed sample exceeds the injection molded behavior for the composition 3/3/3 wt% (CNT/GNP/CB), achieving 40 dB of total attenuation at 11.8 GHz. The findings contribute valuable knowledge into tailoring nanocomposite formulations for additive manufacturing applications in EMI shielding, providing a nuanced understanding of the interplay between processing strategies, nanocomposite morphology, and resulting material properties.

Flexible support material maintains disc height and supports the formation of hydrated tissue engineered intervertebral discs in vivo.

Mechanical augmentation upon implantation is essential for the long-term success of tissue-engineered intervertebral discs (TE-IVDs). Previous studies utilized stiffer materials to fabricate TE-IVD support structures. However, these materials undergo various failure modes in the mechanically challenging IVD microenvironment. FlexiFil (FPLA) is an elastomeric 3D printing filament that is amenable to the fabrication of support structures. However, no present study has evaluated the efficacy of a flexible support material to preserve disc height and support the formation of hydrated tissues in a large animal model. We leveraged results from our previously developed FE model of the minipig spine to design and test TE-IVD support cages comprised of FPLA and PLA. Specifically, we performed indentation to assess implant mechanical response and scanning electron microscopy to visualize microscale damage. We then implanted FPLA and PLA support cages for 6 weeks in the minipig cervical spine and monitored disc height via weekly x-rays. TE-IVDs cultured in FPLA were also implanted for 6 weeks with weekly x-rays and terminal T2 MRIs to quantify tissue hydration at study endpoint. Results demonstrated that FPLA cages withstood nearly twice the deformation of PLA without detrimental changes in mechanical performance and minimal damage. In vivo, FPLA cages and stably implanted TE-IVDs restored native disc height and supported the formation of hydrated tissues in the minipig spine. Displaced TE-IVDs yielded disc heights that were superior to PLA or discectomy-treated levels. FPLA holds great promise as a flexible and bioresorbable material for enhancing the long-term success of TE-IVD implants.

Recycling, thermophysical characterisation and assessment of low-density polythene waste as feedstock for 3D printing

Low-density polyethene (LDPE) is extensively used in single-end-use food packaging and contributes significantly to global waste plastic. This study addresses this challenge by introducing a sustainable approach to reclaim and valorise waste LDPE from milk packaging by converting them into 3D printing filaments. The process involves extruding shredded LDPE pouches into continuous filaments using a modified thermal extruder. The research comprehensively investigates the effects of two key extrusion parameters, nozzle temperature and screw speed, on the resulting filament's physical and mechanical properties. Characterisation efforts include dimensional analysis, morphological evaluation, chemical integrity assessment, thermal stability analysis, and tensile testing. The results show that filaments remain consistently close to 1.75 mm diameter, which is required by most commercial FDM 3D printers. The filaments are chemically intact, thermally stable, and have high toughness across the range of extrusion parameters. The results and a preliminary demonstration of 3D printing indicate that the LDPE waste can be effectively transformed into consistent filaments that have the potential for 3D printing. A carbon footprint assessment underscores the environmental benefits of this approach, showing substantial reductions in estimated CO2 emissions compared to conventional filament production methods. While challenges related to the quality of printed parts remain, the research opens avenues for optimizing 3D printing parameters and exploring multiple recycling cycles. This work represents a step towards sustainable plastic waste management and offers insights into transforming single-use plastic items into valuable resources.