Search Results (104)

Biodegradable polymer composites offer promising alternatives to petroleum-based plastics, supporting the principles of a zero waste and circular economy. This study investigates the reinforcing potential of alkali-treated wood flour derived from recycled pine (Pinus brutia Ten.) and poplar (Populus alba L.) waste wooden pallets in poly(lactic acid) (PLA) biocomposites. Wood flour was initially recovered through grinding and screening during recycling, followed by alkali treatment via a green chemistry approach to enhance interfacial bonding with the PLA matrix. The impact of alkali concentration and two fabrication methods—additive manufacturing (AM) and injection molding (IM)—on the properties of developed biocomposite materials was assessed through mechanical, physical, morphological, and thermal analyses. IM samples outperformed AM counterparts, with the IM PLA containing 30 wt% wood flour (alkali-treated with 10% solution) showing the highest mechanical gains: tensile (+71.35%), flexural (+64.74%), and hardness (+2.62%) compared to untreated samples. Moreover, the AM sample with 10 wt% wood flour and 10% alkali treatment showed a 49.37% decrease in water absorption compared to the untreated sample, indicating improved hydrophobicity. Scanning electron microscopy confirmed that alkali treatment reduced void content and enhanced morphological uniformity, while thermal properties remained consistent across fabrication methods. This work introduces a green composite using non-toxic materials and treatments, facilitating eco-friendly production aligned with zero waste and circular economy principles throughout the manufacturing lifecycle. Full article

In this work, a comparative analysis of polymer test specimens from different types of filaments, manufactured using FDM technology, was performed. A tensile strength test was executed on test specimens after 3D additive printing, made from different groups of materials—PLA, PLA Wood, PETG, PC, PA6, ASA, CPE HG100 and FilaFlex SEBS. Test specimens from the same materials were subjected to accelerated aging, after which they were tested again for tensile strength. The results of all tests were analyzed and compared. Full article

The environmental impact of petroleum-based plastics has driven a global shift toward sustainable alternatives like biodegradable polymers, including polylactic acid (PLA), polybutylene succinate (PBS), and polycaprolactone (PCL). Yet, these bioplastics often face limitations in mechanical and thermal properties, hindering broader use. Reinforcement with cellulose nanofibrils (CNFs) has shown promise, yet most research focuses on conventional sources like wood pulp and cotton, neglecting agricultural residues. This review addresses the potential of maize husk, a lignocellulosic waste abundant in South Africa, as a source of CNFs. It evaluates the literature on the structure, extraction, characterisation, and integration of maize husk-derived CNFs into biodegradable polymers. The review examines the chemical composition, extraction methods, and key physicochemical properties that affect performance when blended with PLA, PBS, or PCL. However, high lignin content and heterogeneity pose extraction and dispersion challenges. Optimised maize husk CNFs can enhance the mechanical strength, barrier properties, and thermal resistance of biopolymer systems. This review highlights potential applications in packaging, biomedical, and agricultural sectors, aligning with South African bioeconomic goals. It concludes by identifying research priorities for improving compatibility and processing at an industrial scale, paving the way for maize husk CNFs as effective, locally sourced reinforcements in green material innovation. Full article

In the face of accelerating urbanization and the growing demand for environmentally responsible materials and designs, this study presents the development and implementation of a modular parklet demonstrator fabricated using dual-material 3D printing. The structure integrates polylactic acid (PLA) and wood-filled PLA (wood/PLA), combining the mechanical robustness of pure PLA in the core with the tactile and aesthetic appeal of wood-based biocomposite on the surface. The newly developed dual-nozzle 3D printing approach enabled precise spatial control over material distribution, optimizing both structural integrity and sustainability. A comprehensive evaluation was conducted for developed filaments and printed materials, including optical microscopy, coupled thermogravimetry analysis and Fourier Transform Infrared Spectroscopy (TG/FTIR), differential scanning calorimetry (DSC), and chemical and mechanical resistance testing. Results revealed distinct thermal behaviors and degradation pathways between filaments and printed parts composed of PLA and PLA/wood. The biocomposite exhibited slightly increased sensitivity to aggressive chemical environments and mechanical wear, dual-material prints maintained high thermal stability and interlayer adhesion. The 3D-printed demonstrator bench and stools were successfully deployed in public spaces as a functional urban intervention. This work demonstrates the feasibility and advantages of using biocomposite materials and dual-head 3D printing for the rapid, local, and sustainable fabrication of small-scale urban infrastructure. Full article

The new wood–plastic composites (WPC) biocomposites, a promising blend of poly(lactic acid) (PLA) and lignocellulosic fillers, are the subject of our study. We used bark and sawdust at 40, 50, and 60% as PLA fillers. The innovative use of ion implantation to modify the surface properties of the produced composites could have significant implications. Argon ions were used in three dosages (1 × 10¹⁵, 1 × 10¹⁶, and 1 × 10¹⁷ cm⁻²) at an accelerating voltage of 60 kV. The modified composites were then analyzed for changes in surface wettability, surface energy, and color. Our findings demonstrate that the dosage of argon ion implantation and the filler used have a profound impact on the properties of the modified surfaces. In general, ion implantation enhances the surface wettability of composites and pure PLA, with the recorded relationships being more pronounced in composites containing higher proportions of lignocellulosic fillers. Furthermore, the implantation of ions on the surface of composites induces changes in their color, opening up new possibilities for the field of materials science. Full article

Particle size of wood fillers used in FDM 3D printing filaments is a topic not commonly discussed in the literature. Research on traditional wood–polymer composites (WPCs) suggests that bigger particles improve the composite’s tensile properties. Is that the case at the 3D printing scale? Five variants of composites were prepared using recycled PLA and sawdust, differentiated by filler particle size (<0.2 mm, 0.2 mm–0.4 mm, 0.4 mm–0.6 mm, 0.6 mm–0.8 mm, 0.8 mm–1 mm). Current draw during extrusion, as well as tensile strength and tensile modulus, were tested. Test results of tensile strength, ranging from 9.21 MPa to 14.28 MPa, and tensile modulus, ranging from 802 MPa to 1014 MPa, have shown no clear correlation between wood particle size and tensile properties of the composites at the 3D printing scale. A clear increase in forces needed to extrude composites containing larger particles of wood was discovered, as well as the inability to extrude composites filled with the biggest tested particle size. To further explore this topic, SEM/EDS imaging of the tested composites was performed. Based on the test results, wood particle sizes ranging from one-fifth to one-half of the nozzle size are recommended for use as fillers in wood–PLA composites intended for 3D printing. Full article

In this study, a modified 3D printer hotend equipped with a load cell, attached to the feeding system, was used to evaluate the effects of filament material composition and printing parameters on the extrusion force required. Four different materials (commercial PLA, pure PLA, wood-PLA with different ratios of wood particles, and wood-PLA with different ratios of thermally modified wood particles) were used for 3D printing, and the feeding resistance was measured. The filament feeder was connected to the extruder hotend via a load cell, which measured the forces required to push the filament through the extruder and the nozzle. Three printing nozzle temperatures of 200, 210, and 220 °C were used. The results show that the printing temperature and the material influence the required extrusion forces, which varied between 1 and 8 N, but the variation was high. With proper optimization and integration into the printer firmware, this setup could also be used to detect nozzle clogging during printing, modify printing parameters during the process, and prevent the uneven extrusion of composite filaments. Full article

Wood plastic composites (WPCs) offer a means to reduce the carbon footprint by incorporating natural fibers to enhance the mechanical properties. However, there is limited information on the mechanical properties of these materials under hostile conditions. This study evaluated composites of polypropylene (PP), polystyrene (PS), and polylactic acid (PLA) processed via extrusion and injection molding. Tests were conducted on tensile and flexural strength and modulus, heat deflection temperature (HDT), and creep analysis under varying relative humidity conditions (10% and 90%) and water immersion, followed by freeze—thaw cycles. The addition of fibers generally improved the mechanical properties but increased water absorption. HDT and creep were dependent on the crystallinity of the composites. PLA and PS demonstrated a superior overall performance, except for their impact properties, where PP was slightly better than PLA. Full article

The present paper investigates the possibility of replacing the traditional L-type corner joint used in chair construction with a 3D printed connector, manufactured using the Fused Filament Fabrication (FFF) method and black PLA as filament. The connector was designed to assemble the legs with seat rails and stretchers, and it was tested under diagonal tensile and compression loads. Its performance was compared to that of the traditional mortise-and-tenon joint. Stresses and displacements of the jointed members with connector were analyzed using non-linear Finite Element Method (FEM) analysis. Both connector and mortise-and-tenon joint were employed to build chair prototypes made from beech wood (Fagus sylvatica L.). Digital Image Correlation (DIC) method was used to analyze the displacements in the vicinity of the jointed members of the chairs. Seat and backrest static load tests were carried out in order to verify if the chairs withstand standard loading requirements. Results indicated that the 3D printed connector exhibited equivalent mechanical performance as the traditional joint. The recorded displacement values of the chair with 3D-printed connectors were higher than those of the traditional chair reaching 0.6 mm on the X-axis and 1.1 mm on the Y-axis, without any failures under a maximum vertical load of approximately 15 kN applied to the seat. However, it successfully withstood the loads for seating and backrest standard tests, in accordance with EN 1728:2012, without any structural failure. This paper presents a new approach for the chair manufacturing sector, with potential applicability to other types of furniture. Full article

This article examines how water content is a crucial parameter for the preservation of wooden artworks and buildings, focusing on non-invasive ways of measuring water content through capacitive methods. A personalized, low-cost probe to measure the dielectric properties of oak and poplar wood at various water content levels and frequencies is described. The accuracy of the probe is confirmed by testing it with reference materials like air, PTFE, PLA, glass and Bakelite, demonstrating an accuracy error below 2%. Next, the probe is used to evaluate the relationship between water content and permittivity, indicating possible uses in conservation projects. Measurements were conducted on two types of wood, poplar and oak, at five varying levels of water content. The dielectric permittivity between 10 and 100 kHz was assessed. Using the vertical shift from the single interpolant of the dataset, a graduation curve was estimated. Finally, an R² = 0.98 value demonstrates that a sigmoidal function reflects the relationship between the percentage water content and the permittivity of materials. Full article

In the industry sector, it is very common to have different types of dissimilar materials on the same construction rather than products made from a single type of material. Traditional methods (welding, mechanical fastening, and adhesive bonding) and hybrid techniques (friction stir welding, weld bonding, and laser welding) are used in the assembly or joining of these materials. However, while joining similar types of materials is relatively easy, the process becomes more challenging when joining dissimilar materials due to the structure and properties of the materials involved. In recent years, additive manufacturing and 3D printing have revolutionized the manufacturing landscape and have provided great opportunities for the production of polymer-based multi-materials. However, developments in the joining of multi-material parts are limited, and their limits are not yet clear. This study focuses on the joining of 3D-printed products made from PLA-based multiple materials (PLA and PLA Wood) using friction stir welding. Single-material and multi-material parts (with 100% infill ratio and three different combinations of 50% PLA/50% PLA Wood) were welded at a feed rate of 20 mm/min and three different tool rotational speeds (1750, 2000, and 2250 rpm). Tensile and bending tests were conducted on the welded samples, and temperature measurements were taken. The fractured surfaces of the samples were examined to perform a damage analysis. It is determined that the weld strength of multi-materials changes depending on the combination of the material (material design). For multi-materials, a welding efficiency of 74.3% was achieved for tensile strength and 142.68% for bending load. Full article

The interlayering method effectively enhances resistance against delamination in laminated composites. However, synthesis methods for interlayers have been limited and, at times, expensive. Consequently, this study investigates the effect of innovative 3D-printed wood–PLA interlayers on the mode II interlaminar fracture toughness (ILFT) of glass/epoxy composites. These interlayers feature a geometric structure comprising rhomboidal cell shapes, enabling the filament to maintain an equal volume percentage to the resin at the delamination interface. To this end, end-notch flexure (ENF) specimens were prepared, and the mode II ILFT was determined using the compliance-based beam method. The experimental results demonstrate a substantial increase in initiation load tolerance ($\cong 32$%) due to the 3D-printed interlayer. The R-curve analysis of the specimens with interlayers reveals significant enhancement in critical delamination parameters, including the length of the fracture process zone ($\cong 23\%$), initiation ILFT ($\cong 80\%$), and propagation ILFT ($\cong 44\%$), compared to the samples without interlayers. The fracture surface analysis of the reinforced specimens with interlayers demonstrated that the interlayer positively impacts the delamination resistance of the ENF specimens. They create a larger resin-rich area and increase surface friction at the delamination interface. Also, this facilitates a crack front pinning mechanism and changes the direction of crack growth. Full article

Wood flour-paired poly(lactic acid) (PLA)-based biocomposites were fabricated with filler contents of 0, 2.5, 5, 10, and 20 wt.%. The samples were processed through extrusion followed by injection molding. The injection-molded specimens were subjected to tensile tests, impact tests, and water absorption tests. Based on the results, increasing the amount of lignocellulose fibers effectively improved the modulus of PLA from 2.8 to 3.6 GPa at 20 wt.% wood flour loading; however, this came at the cost of strength, which dropped from 55.0 to 48.8 MPa. Additionally, the incorporation of lignocellulose increased the hydrophilicity of the composites, resulting in a threefold increase in water absorption at 10 wt.% filler content. These results provide insight into the effects of embedding lignocellulose fibers into PLA. Full article

Fused deposition molding (FDM) is a commonly used 3D printing method, and polylactic acid (PLA) has become one of the most important raw materials for this technology due to its excellent warping resistance. However, its mechanical properties are insufficient. Polybutylene adipate terephthalate (PBAT) is characterized by high toughness and low rigidity, which can complement the performance of PLA. The biodegradable polymers produced by blending the two have thus been used to replace petroleum-based plastics in recent years, but the high cost of the blends has limited their wide applications. Introducing plant fibers into the blends can not only maintain biodegradability and improve the overall performance of the plastics but also reduce their costs greatly. In this study, the PBAT/PLA blends with a mass ratio of 70/30 were selected and mixed with wood flour (WF) to prepare ternary composites using a FDM 3D printing technique. The effects of WF dosage on the mechanical properties, thermal properties, surface wettability, and melt flowability of the composites were investigated. The results showed that the proper amount of WF could improve the tensile and flexural moduli of the composites, as well as the crystallinity and hydrophobicity of the printed specimens increased with the content of WF, while the melt flow rate decreased gradually. Compared to PBAT/PLA blends, WF/PBAT/PLA composites are less costly, and the composite containing 20 wt.% WF has the best comprehensive performance, showing great potential as raw material for FDM 3D printing. Full article

This study investigated the closed-loop recycling of 3D-printed wood fiber (WF)-filled polylactic acid (PLA) composites via fused filament fabrication (FFF). The WF–PLA composites (WPCs) were extruded into WPC filaments (WPC_fs) to produce FFF-printed WPC parts (WPC_ps). The printed WPC_ps were reprocessed three times via extrusion and 3D-printing processes. The tensile properties and impact strengths of the WPC_fs and WPC_ps were determined. To further investigate the impact of closed-loop recycling on the surface morphology, crystallinity, and molecular weight of WPC_fs, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC), respectively, were used. After closed-loop recycling, the surface morphology of the WPC_fs became smoother, and a decrease in the pore sizes was observed; however, the tensile properties (tensile strength and elongation at break) deteriorated. With increasing numbers of recycling iterations, the molecular weight of the PLA matrix decreased, while an increase in crystallinity was observed due to the recrystallization of the low-molecular-weight PLA molecules after recycling. According to the SEM images of the recycled WPCps, their layer heights were inconsistent, and the layers were rough and discontinuous. Additionally, the color difference (ΔE*) of the recycled WPC_ps significantly increased. Compared with those of the WPC_ps after recycling them only once, the tensile strength, elongation at break, and impact strength of the WPC_ps noticeably decreased after recycling them twice. Considering the changes in various properties of the WPC_fs and WPC_ps, the FFF-printed WPC parts can be reprocessed only once through 3D printing. Full article