Search Results (2,514)

The design of sustainable polymer systems with tunable properties is essential for next-generation functional materials. This study examines the influence of a phenol-free modified rosin resin (Unik Print™ 3340, UP)—a maleic anhydride- and fumaric acid-modified gum rosin—on the structural, thermal, rheological, and mechanical behavior of four poly(lactic acid) (PLA) grades with different molecular weights and crystallinity. Blends containing 3 phr of UP were prepared by melt compounding. Thermogravimetric analysis showed that the incorporation of UP did not alter the thermal degradation of PLA, confirming stability retention. In contrast, differential scanning calorimetry revealed that UP affected thermal transitions, suppressing crystallization and melting in amorphous PLA grades and shifting the crystallization temperature to lower values in semi-crystalline grades. The degree of crystallinity decreased for low-molecular-weight semi-crystalline PLA but slightly increased in higher-molecular-weight samples. Mechanical tests indicated that UP acted as a physical modifier, increasing toughness by over 25% for all PLA grades and up to 60% in the amorphous, low-molecular-weight grade. Rheological measurements revealed moderate viscosity variations, while FESEM analysis confirmed microstructural features consistent with improved ductility. Overall, UP resin enables fine tuning of the structure–property relationships of PLA without compromising stability, offering a sustainable route for developing bio-based polymer systems with enhanced mechanical performance and potential use in future biomimetic material designs. Full article

Additive manufacturing (AM) has rapidly evolved due to its design flexibility, ability to enable personalized fabrication, and reduced material waste. In the medical field, fused filament fabrication (FFF) facilitates the production of individualized anatomical models for surgical preparation, education, medical imaging, and calibration. However, the lack of filaments with X-ray attenuation similar to that of biological hard tissues limits their use in radiological imaging. To address this limitation, a radiopaque filament was developed by incorporating gadolinium oxide (Gd₂O₃) into a biodegradable poly(lactic acid) (PLA) matrix at 1, 3, and 5 wt.%. Thermal and rheological properties were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and melt flow index (MFI) analyses, revealing minor variations that did not affect printability under standard FFF conditions (200 °C nozzle, 60 °C build plate, 0.12 mm layer height). Microstructural analysis via field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), elemental mapping, and micro-computed tomography (micro-CT) confirmed homogeneous Gd₂O₃ dispersion without nozzle blockage. Radiopacity was evaluated using gyroid infill cubes, and increasing Gd₂O₃ content enhanced X-ray attenuation, with 3 wt.% Gd₂O₃ reaching Hounsfield Unit (HU) values comparable to cortical bone. Finally, the L1 vertebra phantom fabricated from the 3 wt.% Gd₂O₃ filament exhibited mean HU values of approximately +200 to +250 HU at 50% infill density (trabecular bone region) and around +1000 HU at 100% infill density (cortical bone region), demonstrating the filament’s potential for producing cost-effective, radiopaque, and biodegradable phantoms for computed tomography (CT) imaging. Full article

The issue of antibiotic resistance is becoming increasingly severe, urgently requiring the development of new antibacterial strategies. Photodynamic therapy (PDT) has gradually emerged as a promising alternative due to its spatiotemporal controllability, low risk of drug resistance, and broad-spectrum antibacterial properties. However, most existing photosensitizers (PSs) are hydrophobic, which limits their application efficiency in PDT. To address this problem, we designed and synthesized a water-soluble perylene diimide derivative (PDICN-CBn) as a photosensitizer. By introducing quaternary ammonium salt groups, its water solubility was improved, and antibacterial activity was enhanced. Subsequently, PDICN-CBn was assembled into silk fibroin/polylactic acid (SF/PLA) nanofibrous membranes via electrospinning technology, successfully constructing a visible-light-responsive ternary composite nanofibrous membrane (SF/PLA@PDICN-CBn). Using various characterization methods such as nuclear magnetic resonance (¹H-NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), the microstructure, chemical composition, and structural characteristics of the nanofibrous membranes were systematically analyzed, verifying the successful synthesis of the photosensitizer and its assembly into the nanofibrous membranes. In the reactive oxygen species (ROS) experiment, electron spin resonance (ESR) spectra showed that PDICN-CBn efficiently generated singlet oxygen (¹O₂), superoxide anion (·O₂⁻), and hydroxyl radical (·OH) under visible light irradiation, confirming its ability to produce different types of ROS through both type I and type II photodynamic reactions. In the antibacterial experiments, Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and methicillin-resistant Staphylococcus aureus (MRSA) were selected for a series of tests, including plate-counting antibacterial assays, bacterial live/dead staining, and SEM observation of morphology. The results showed that 8 μg/mL of PDICN-CBn effectively destroyed the bacterial cell membrane structure and killed bacteria (bactericidal rate > 95%) after 2 h of visible light irradiation. This work successfully developed a novel visible-light-responsive SF/PLA@PDICN-CBn nanofibrous membrane with a dual antibacterial system combining photodynamic and electrostatic adsorption antibacterial properties, providing new ideas and methods for the design and development of photodynamic antibacterial materials. The prepared nanofibrous membrane has potential application values in fields such as wound dressings and medical protective materials and is expected to provide strong support for solving clinical infection problems. Full article

Polylactic acid (PLA) is a biodegradable polymer with an ever-increasing number of applications, although its inherent brittleness limits its performance somewhat in structural applications. In this study, we analysed the influence of incorporating multi-walled carbon nanotubes (MWCNTs) and halloysite nanotubes (HNTs) at different concentrations (0.5, 0.75 and 1 wt%) on the mechanical properties of injection-moulded PLA nanocomposites. The effects of the nanofillers were characterised by tensile, flexural, and impact tests, hardness measurements, and FESEM examination. The results showed that MWCNTs increased the flexural strength and stiffness by up to 60% compared to neat PLA (84.3 vs. 52.6 MPa), although this was accompanied by a reduction in elongation at break (from 2.30% to 1.57%) due to agglomeration. Conversely, HNTs improved the elongation at break up to 6.39%, enhanced flexural strength by approximately 62% (85.1 MPa), and maintained stiffness around 3.0 GPa, indicating a better balance between strength and ductility. The FESEM micrographs confirmed the presence of clusters in MWCNTs and a more homogeneous dispersion in HNTs, thus explaining the differences in behaviour. Overall, MWCNTs are more suitable for applications requiring high stiffness and strength, whereas HNTs are preferable when greater ductility and impact resistance are required. Full article

Lightweight and lead-free radiation shields are increasingly developed to overcome the toxicity and handling challenges associated with conventional heavy-metal-based materials. In this study, the $\gamma$-ray attenuation behavior of polymer–zeolite composites was examined by reinforcing high-density polyethylene (HDPE) and polylactic acid (PLA) with natural clinoptilolite zeolite at concentrations of 10–40 wt%. Photon-interaction parameters, including the linear attenuation coefficient ($\mu$), half-value layer (HVL), mean free path ($\lambda$), and effective atomic number ($Z_{\mathrm{eff}}$), were evaluated over 15 keV–15 MeV using the Phy-X/PSD platform. Zeolite incorporation consistently enhanced photon attenuation, particularly at low energies dominated by the photoelectric effect. At 15 keV, the HVL decreased from 0.60 cm to 0.08 cm for HDPE and from 0.043 cm to 0.033 cm for PLA as the zeolite loading increased to 40 wt%. Correspondingly, $Z_{\mathrm{eff}}$ increased from 2.7 to 4.3 for HDPE and from 6.5 to 11.6 for PLA, while $\mu$ reached approximately 41 cm⁻¹ and 56 cm⁻¹ at 15 keV for the respective 40 wt% composites. Beyond about 1 MeV, differences between compositions became minimal as Compton scattering dominated. PLA–zeolite composites exhibited higher $\mu$ and lower HVL than HDPE–zeolite, whereas HDPE maintained an advantage in mixed-field environments owing to its hydrogen-rich matrix. The results confirm that zeolite-reinforced polymers are safe, low-cost, and lightweight materials suitable for radiation shielding in medical, nuclear, and aerospace applications. Full article

The continuously growing amount of oily wastewater from industrial, domestic, and natural sources poses a major threat to water sustainability, and thus efficient oil–water separation techniques are of utmost relevance. Membrane separation has been a popular approach due to ease of handling, high performance, and versatility. Among all the membrane materials, polylactic acid (PLA) and its derivatives have been of interest as green materials because of their renewability, biocompatibility, and biodegradability. PLA possesses special merits, including low density, high permeability, and high thermal stability. Despite its advantages, PLA also has some demerits, such as brittleness, low tensile strength, and poor heat resistance. These limitations are addressed by PLA-based membranes that are generally reinforced using fillers, surface modification, and structure optimization methods. This review provides a comprehensive overview of recent developments of PLA and its derivatives for oil–water separation, with an emphasis on membrane design, fabrication methods, and porosity enhancement strategies. Some significant fabrication processes like Thermally Induced Phase Separation (TIPS), Nonsolvent-Induced Phase Separation (NIPS), and Freeze Solidification Phase Separation (FSPS) are elaborately addressed. In addition, the review emphasizes methods to improve porosity, mechanical strength, and fouling resistance while maintaining biodegradability. By reviewing recent progress and remaining challenges, this review outlines the future potential of PLA membranes and aims to inspire more research on green, efficient oil–water separation. Full article

Environmental concerns about plastic waste have increased interest in biobased and biodegradable polymers such as polylactic acid (PLA) and polybutylene succinate (PBS). Blending PLA and PBS can provide a balanced performance, offsetting the PLA’s brittleness. PLA/PBS can be processed either via single-screw extrusion (SSE) or twin-screw extrusion compounding followed by SSE (TSSE). This study aims at a comprehensive investigation of these two processing routes and assesses their impact on the physical, morphological, and mechanical properties of PLA/PBS blends. The results indicate that while both routes produce blends with comparable overall performance, subtle differences exist in the degradation behavior of PLA and the morphology of the blends. The PLA molecular weight drop was more pronounced in TSSE (~18.7%) compared to SSE (~1.5%). In both processing routes, PBS exhibited sub-micrometer domains below 15 wt.% loading, beyond which a distinct sea–island morphology with larger PBA domains was observed. TSSE exhibited slightly finer PBS domains. However, these differences did not lead to significant mechanical performance or miscibility differences. For instance, with 15 wt.% PBS loading, the elongation at break was improved from 4.6% to 193% in SSE15 and 192% in TSSE15, with a 29% and 30% decrease in yield strength, respectively. This work suggests that the single-step SSE process can be used as a cost-effective and energy-saving approach in PLA/PBS blending without the need for pre-compounding. Full article

Isolating the mechanical properties of an FDM joint by performing a direct tensile test on it is something that has yet to be achieved. Developing a methodology for isolating the properties of a single joint could help to inform simulations and achieve a better understanding of the mechanisms affecting the bond strength between FDM-printed materials. In this work, a cruciform single-joint test (CSJT) of a cross-shaped specimen and a fast mechanical clamping protocol are introduced to evaluate the apparent tensile strength and fracture mechanisms of a single FDM-printed joint between two PLA filaments. First, a discussion of different approaches for obtaining a fast, reproducible, and reliable test of the samples is presented. Then, nozzle temperature (180–215 °C) and bed temperature (30–120 °C) were systematically varied, producing a minimum of n = 12 samples per condition. Samples were classified after failure, depending on the fracture mechanism (type 1 = joint failure; type 2 = filament failure), and the apparent tensile strength (ATS) of the joint was computed from the tensile tests and optical micrographs. The detachment probability of the joints decreased sharply above 210 °C, while the ATS increased, approaching a plateau near ~50 MPa. The influence of bed temperature was smoother, with a stable decrease in the detachment ratio as the ATS increased, indicating that nozzle temperature is the main factor contributing to the joint strength. These results map a temperature-driven transition from joint-controlled to filament-controlled failure. The method proposed also provides a minimal-material, high-throughput route to quantify FDM interlayer bonding and inform process simulations. Additional tests are performed to contextualize the results presented. Full article

The environmental impact of petroleum-based plastics has accelerated the search for sustainable alternatives in food packaging. Polylactic acid (PLA), a biobased and compostable polymer, is among the most promising candidates, yet its inherent brittleness and poor moisture barrier limit its application in high-humidity contexts such as dairy packaging. This study investigates immiscible PLA/poly(butylene succinate-co-adipate) (PBSA) blend films as potential biobased packaging materials for perishable foods. Even if these blends have been already studied, limited attention has been given to the systematic characterization of the baseline barrier properties of unmodified PLA/PBSA blends in contact with liquid dairy products. Four blend ratios (PLA/PBSA = 30/70, 40/60, 50/50, 60/40 wt%) were prepared via micro-compounding and compression molding. The films were characterized through melt flow analysis, FTIR, SEM, DSC, DMTA, and tensile testing to evaluate their thermal, morphological, and mechanical properties. Crucially, moisture barrier performance was assessed under simulated dairy conditions by sealing fresh whey at 4 °C and monitoring weight loss over 30 days. Results revealed that while tensile strength and storage modulus (E’) decreased nearly linearly with increasing PBSA content, elongation at break exhibited a non-linear trend, highlighting the complex interplay between blend morphology and mechanical behavior. The study provides a baseline understanding of neat PLA/PBSA blends in contact with liquid dairy, identifying the most promising formulations for future scale-up. These findings contribute to the development of biodegradable packaging systems tailored for refrigerated, high-moisture food applications Full article

Polylactic acid (PLA) and its composites with hydroxyapatite (HA) have been studied in the field of bone repair applications. The objective of this study was to evaluate the biocompatibility of PLA/HA at different concentrations and to analyze early adhesion of periodontal ligament stem cells (PDLSCs). Cells were seeded in two 24-well plates, each containing six disk-shaped samples of PLA/HA (10%, 15% and 20%) and six control samples and then examined using scanning electron microscopy. Twelve 96-well plates were prepared with different elution concentrations (1/1, 1/2, 1/4, and 1/8) to assess biocompatibility using MTT cell viability and Hoechst 33342 assays at 24, 48, and 72 h. PLA/HA 20% showed the highest early adhesion (p = 0.0057), with cells adopting a more elongated morphology. The MTT assay revealed no differences in viability between concentrations (p = 0.6196), whereas the Hoechst assay demonstrated the highest viability for PLA/HA 20% (p < 0.0001). Overall, PLA promoted cell adhesion, with the 20% formulation providing the greatest adhesion. All concentrations maintained high viability, and longer culture time enhanced both adhesion and viability. Full article

This study analyzes the influence of material extrusion (MEX) 3D printing and ironing parameters on parts made of polylactic acid (PLA), such as top surface roughness and flatness. Surface ironing is one of the post-processing methods. It is an interesting alternative to the most commonly used mechanical or chemical treatments. It does not require the use of any additional devices or substances; however, it can only be used on flat surfaces, requires additional time for application, and a flush may form at the edges of the ironed surface. The Response Surface Methodology (RSM) was used for modeling the analyzed processes. The presented methodology assumes a two-stage approach. First, the printing process of the top surface is optimized. Then, the ironing of the top surface is optimized. Improvement of surface roughness and flatness was adopted as the optimization criterion. The influence of extruder temperature, printing speed, and filament flow used during printing of the top surface, as well as extruder temperature, ironing speed, and distance between passes used during ironing, was examined. The significance of the influence of the analyzed parameters was determined using ANOVA and Pareto diagrams. The use of the applied research methodology and created mathematical models allows for determining the relationship between the optimal extruder temperature, extrusion flow, speed, and distance between passes during ironing while ensuring high process efficiency. The ironing resulted in a fivefold reduction in the Ra and an eightfold reduction in the FLTq parameters. A surface with Ra = 1.09 μm and FLTq = 3.4 μm was obtained. Full article

This research addresses the inherent limitations of low mechanical strength in FDM-printed materials by studying Carbon Fibre-reinforced Polylactic Acid (PLA-CF) composites. The low strength limitation of PLA-CF in FDM requires identifying the most suitable print angle and layer height parameters. This study maximises its structural robustness, filling a knowledge gap regarding its combined effect on tensile and flexural strength. The main objective was to find the best printing angle and layer height to improve mechanical performance, an important requirement for advancing additive manufacturing applications. A total of 210 FDM-printed specimens of the PLA-CF material were subjected to uniaxial tensile (ASTM D3039) and three-point bending (ASTM D790) tests, systematically varying the printing angles (0–90°) and layer heights of 0.1, 0.2, and 0.3 mm, following a full experimental design matrix. The ANOVA method has been used to determine the significant effect of factors on the established parameters. The findings indicated that both factors had a pronounced effect on the mechanical strength. Printing at lower angles (0° and 15°) provided, on average, greater resistance under tension (up to ~3920 N for a layer height of 0.1 mm), as well as under bending (up to 88.54 N for the same layer height), attributed to favourable fibre alignment and better load distribution. Conversely, higher angles (60° to 90°) drastically reduced strength (tensile failures due to delamination; bending forces as low as 30.02 N for a layer height of 0.3 mm, highlighting the weakness of perpendicular layer interfaces. Furthermore, lower layer height could result in better overall mechanical properties. In conclusion, FDM parameters with low print angles and reduced layer heights are essential for maximising the mechanical robustness and structural integrity of PLA-CF parts, enabling the identification of improved production processes for industrial applications and educational prototypes, among others. Full article

Polylactic acid (PLA), a widely used biobased biopolymer, is highly resistant to biodegradation under ambient conditions, contributing to persistent plastic pollution and posing potential environmental and health risks. This study investigates the enzymatic degradation of PLA by Proteinase K, a proteolytic hydrolase enzyme with the ability to degrade PLA, and explores the underlying mechanisms for degradation. Both amorphous and semi-crystalline PLA were treated with Proteinase K (2 mg/mL) at 37 °C over varying time periods. PLA degradation was evaluated using multiple techniques, including weight loss measurement, pH reduction, quantification of lactic acid monomer release by High-Performance Liquid Chromatography (HPLC), surface morphology analysis through Scanning Electron Microscopy (SEM), changes in thermal properties by Differential Scanning Calorimetry (DSC), and structural changes by X-Ray Diffraction (XRD). The data revealed that the degradation of amorphous regions of the PLA polymer was faster and more extensive than the crystalline regions of the polymer. Repeated enzymatic treatments significantly enhanced the degradation rate. Furthermore, Proteinase K showed a clear preference for degrading amorphous regions of the PLA, as evidenced by higher weight loss, sharper pH decline, higher lactic acid production, and more pronounced surface disruptions, such as visible gaps between degraded oligomer structures. Full article

The contamination of water by heavy metals is a global problem with distressing health consequences, and researchers have proposed various methods to remove these ions. This study explored poly (lactic acid) (PLA)/ethylene vinyl acetate (EVA)/graphene oxide (GO) composites as possible adsorbents of lead ions from water. GO was synthesized using modified Hummer’s method, and melt mixing was used to prepare the polymer blends and composites. Morphology investigations showed that PLA and EVA were immiscible, GO preferred to settle on the interface between the two polymers, and GO had a partial miscibility and compatibility effect on the polymers, even though cracks and voids were observed with increasing GO content. In water absorption studies, the early hydrolytic degradation of PLA was avoided by incorporating EVA, resulting in reasonable water absorption rates. The 50/50 w/w PLA/EVA blend and its composites showed a high-water intake. In Pb(II) adsorption studies using AAS, all the analyzed samples had very high Pb(II) adsorption capacities, and the 66.5/28.5/5 w/w PLA/EVA/GO composite adsorbed the most lead ions, under basic media, and a 5 h contact time. Adsorption kinetic modeling suggested that a homogenous adsorption process took place, with a precise Langmuir isotherm. The developed materials are promising commercial lead ion adsorbents that are environmentally friendly. Full article

The technology of 3D printing has become one of the most effective methods of creating various parts, such as those used for fast prototyping. The most important aspect of 3D printing is the selection and application of the appropriate material, also known as filament. The current review concerns mainly the description of the mechanical and physical properties of the different filaments and the possibilities of improving those properties. The review begins with a short description of the development of 3D printing technology. Next, the basic characteristics of thermoplastics used in the fused filament fabrication (FFF) are discussed, namely polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyethylene terephthalate glycol (PETG). According to modern concepts, the printed parts can be reinforced with the use of different kinds of fibers, namely synthetic fibers (carbon, glass, aramid) or natural fibers (wood, flax, hemp, jute). Thus, the impact of such a reinforcement on the performance of FFF composites is also presented. The current review, unlike other works, primarily addresses the problem of the aging of parts made from the thermoplastics above. Environmental conditions, including UV radiation, can drastically reduce the physical and mechanical properties of printed elements. Moreover, the current review contains a detailed discussion about the influence of the different fibers on the final mechanical properties of the printed elements. Generally, the synthetic fibers improve the mechanical performance, with documented increases in tensile modulus reaching, for instance, 700% for carbon-fiber-reinforced ABS or over 15-fold for continuous aramid composites, enabling their use in functional, load-bearing components. In contrast, the natural ones could even decrease the stiffness and strength (e.g., wood–plastic composites), or, as in the case of flax, significantly increase stiffness (by 88–121%) while offering a sustainable, lightweight alternative for non-structural applications. Full article