Fused deposition modelling is a rapidly growing additive manufacturing technology due to its ability to build functional parts having complex geometries. The mechanical properties of a built part ...depend on several process parameters. The aim of this study is to characterize the effect of build orientation, layer thickness and feed rate on the mechanical performance of PLA samples manufactured with a low cost 3D printer. Tensile and three-point bending tests are carried out to determine the mechanical response of the printed specimens.
Due to the layer-by-layer process, 3D printed samples exhibit anisotropic behaviour. Upright orientation shows the lowest mechanical properties. On the other hand, on-edge and flat orientation show the highest strength and stiffness. From a layer thickness and feed rate point of view, it is observed that ductility decreases as layer thickness and feed rate increase. In addition, the mechanical properties increase as layer thickness increases and decrease as the feed rate increases for the upright orientation. However, the variations in mechanical properties with layer thickness and feed rate are of slight significance for on-edge and flat orientations, except in the particular case of low layer thickness. Finally, the practicality of the results is assessed by testing an evaluation structure.
Display omitted
•The effect of 3D printing process parameters on the mechanical performance of PLA samples is assessed.•On-edge oriented samples show the optimal mechanical performance.•Ductility decreases as layer thickness and feed rate increase.•Low layer thickness and high feed rate values are recommended for the optimal mechanical performance.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Bone defect caused by trauma, tumor, infection, and other reasons is a thorny problem that needs to be solved in orthopedic clinic. Customized bone repair biomaterials and their fabrication still ...need to be explored. Three-dimensional (3D) printing is a high-speed fabrication process for bone tissue biomaterials, which paves the way of solving clinical bone defect problems in a new way. In this study, the fused deposition modeling (FDM) technology was used to prepare the composite scaffolds of polylactic acid (PLA) and nano-hydroxyapatite (n-HA). The composite scaffold was optimized by material characterization, mechanical property test, and in vitro bone marrow mesenchymal stem cells biocompatibility test. Finally, a rabbit model was established to evaluate the osteogenic ability of PLA/n-HA scaffolds in vivo. The results showed that the PLA/n-HA composites proposed in this study were highly printable, and the printed scaffold showed tunable mechanical strength accompanied by the proportion of n-HA components. The biocompatibility and osteogenic induction properties were proved better than that of the pure PLA scaffold. This composite scaffold of PLA and n-HA provides a promising strategy for the repair of large bone defects.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Display omitted
•More oxygen-containing functional groups exhibited on the surface of PLA MPs after degradation.•Degraded PLA without biofilms had the highest adsorption amount due to enhanced ...hydrogen bonding.•Microbial adhesion increased adsorption capacity of PLA MPs through OTC chemical complexation.•OTC adsorption capacity of PLA MPs first increased and then decreased with the pH of 3.0–9.0.•The presence of FA suppressed the adsorption of OTC on PLA MPs.
Biodegradable plastics have been evaluated as promising alternatives for conventional polymers in various fields. Although microplastics (MPs) have been reported as vectors for pollutants in the environment (e.g. antibiotics), knowledge about the chemicals carrying mechanisms of degradable MPs during the biodegradation process is limited. In this study, we investigated the adsorption behavior of oxytetracycline (OTC) on polylactic acid (PLA) MPs during its biodegradation process. Scanning electron microscopy (SEM) discovered the growth of scattered rod-shaped bacteria on the surface of PLA MPs. Two-dimensional correlation spectroscopy (2D-COS) combined with Fourier transform infrared spectroscopy (FTIR) identified the breakage of ester linkages and the generation of more oxygen-containing functional groups, indicating PLA biodegradation occurred. The presence of a biofilm coating increased the OTC adsorption capacity on MPs by 20.15%, mainly due to OTC complexing with chemical functional groups existing in biofilms (e.g. N–H functional group). More oxygen-containing functional groups were exposed on the surface of PLA MPs after removing biofilms, which further increased the adsorption quantity of OTC by 39.01% through enhanced hydrogen bonding compared with biofilm coating MPs. The adsorption quantity of OTC adsorbed onto MPs first increased and then decreased with the pH ranging from 3.0 to 9.0, which was dominated by electrostatic interaction and hydrophobic interaction. In addition, the adsorption capacity of MPs was suppressed by the presence of fulvic acid (FA) due to that the adsorbed FA blocked further OTC adsorption and OTC showed higher affinity to free FA compared with MPs. These results unravel the OTC adsorption behavior of PLA MPs undergoing microbial adhesion and degradation, which could be useful for understanding the environmental sorption behavior of degradable MPs.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this paper, a bio-based flame retardant PA-AR is synthesized, which endows PLA with good flame retardant and crystallization properties, and at the same time promotes the biodegradability of PLA. ...Only 1 wt% PA-AR makes the LOI value of PLA reach 26.8% and reaches UL-94 V-0 level. In addition, 1 wt% PA-AR increases the crystallinity of PLA to 23.4%, which increased by 460% compared with PLA. Further, due to the increase of crystallinity, the tensile strength is also improved. Besides, the addition of PA-AR can greatly promote the degradation performance of PLA under specific biological conditions. This work proposed a novel method to obtain completely biodegradable flame retardant composites.
Display omitted
•A bio-based compound is synthesized in aqueous phase as a flame retardant for PLA.•1 wt% addition of flame retardant can make PLA composite self-extinguish and enhance LOI value.•The flame retardant endows PLA with excellent crystallization.•The flame retardant significantly promotes the biodegradation rate of PLA.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To achieve optimum functionality and mechanical properties of advanced manufacturing-based scaffolds for biomedical application, it is important to study their mechanical strength by 3D-printing at ...different orientations. This study examined the effects of printing at different orientations on the mechanical properties of synthesized 3D-polylactic acid (PLA) and hydroxyapatite-modified PLA (PLA-HAp) scaffolds. A total number of 30 samples were printed in three orientations on the XY plane: 0°, 45°, and 90°. Finite element modeling and simulation was employed to identify the strongest scaffold in terms of compression strength, which is the primary criterion for load bearing bone tissue scaffolds. These findings indicate that 3D-printing at an orientation of 90° on the XY plane resulted in a scaffold with the highest compression strength. Moreover, the fabricated PLA scaffolds showed very poor cell attachment and proliferation on their surface, which is not suitable for their biomedical application. This study additionally showed the optimization of a very simple post-fabrication modification technique with nano HAp for better cell attachment and proliferation with enhanced mechanical properties. The post-fabrication modification of PLA scaffolds by nano-HAp results in excellent cell attachment property with enhanced mechanical strength and stability of up to 47.16% for 90° 3D-printed PLA-HAp scaffolds.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Lactide is a vital monomer for producing high molecular weight polylactic acid (PLA) through ring‐opening polymerization. This study synthesized crude lactide from L‐lactic acid with MIL‐101 as the ...catalyst. MIL‐101 is a metal‐based catalyst with organic ligands (MOF) that was prepared by reacting Cr(NO3)3.9H2O with terephthalic acid (BDC). The formation of MIL‐101 was confirmed from Fourier‐transform infrared (FTIR) analysis. The role of MIL‐101 and the effect of temperature, time, and MIL‐101 loading, as well as their interactions in the conversion of lactic acid to crude lactide, were then investigated using the response surface method (RSM). Crude lactide was analyzed using 1H‐nuclear magnetic resonance (NMR) spectroscopy to confirm the presence of lactide. The RSM results indicated that the highest conversion of 22.84% can be obtained using a temperature of 175 °C, 1.5% w/w MIL‐101 loading, and a reaction time of 5 h. The RSM model showed that the interaction of MIL‐101 loading and reaction time strongly affected the conversion of lactic acid to lactide, with a P‐value of 0.0021 and an F‐value of 50.45. In contrast, the interaction of catalyst loading and temperature did not significantly affect the conversion of lactic acid to lactide, with a P‐value of 0.2565 and an F‐value of 1.75.
Plastics play an essential role in food packaging; their primary function is to preserve the nature of the food, ensure adequate shelf life and ensure food safety. Plastics are being produced on a ...global scale in excess of 320 million tonnes annually, with demand rising to reflect the material in wide range of applications. Nowadays, the packaging industry is a significant consumer of synthetic plastic made from fossil fuels. Petrochemical-based plastics are regarded as the preferred material for packaging. Nonetheless, using these plastics in large quantities results in a long-standing environment. Environmental pollution and the depletion of fossil fuels have prompted researchers and manufacturers to develop eco-friendly biodegradable polymers to replace petrochemical-based polymers. As a result, the production of eco-friendly food packaging material has sparked increased interest as a viable alternative to petrochemical-based polymers. Polylactic acid (PLA) is one of the compostable thermoplastic biopolymers that is biodegradable and renewable in nature. High-molecular-weight PLA can be used to produce fibres, flexible, non-wovens, hard and durable materials (100,000 Da or even higher).The chapter focuses on food packaging techniques, food industry waste, biopolymers, their classification, PLA synthesis, the importance of PLA properties for food packaging, and technologies used to process PLA in food packaging.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Last years have witnessed great advances in minimizing the flammability of the polylactic acid (PLA) bioplastic. Unfortunately, to date there remains an urgent lack of a facile strategy to develop ...highly effective flame retardants for PLA. Herein, we report one-pot scalable fabrication of an oligomeric phosphoramide, phenyl phosphonic piperazine (PPP), via a one-step condensation polymerization. PPP can finely disperse within the PLA matrix showing a submicron-grained structure with a domain size of 100–300 nm. The addition of 3 wt% PPP increases the limiting oxygen index (LOI) of PLA to 32.5 vol%, and a V-0 rating is achieved. Such high flame retardancy is mainly attributed to the free radical quenching, gas dilution and the thermal barrier action of the char layer. Moreover, the PLA/3%PPP composite retains a tensile strength of 55.4 MPa. This work provides a facile and scalable approach to preparing high-performance flame retardant PLA materials.
Display omitted
•An oligomeric polyphosphoramide (PPP) was facilely synthesized by a one-pot condensation reaction.•The PLA/PPP composites exhibit unique submicron-grained microstructures.•Adding only 3 wt% PPP enables PLA to achieve V-0 rating and an LOI value as high as 32.5%.•The flame retardancy of PPP is mainly attributed to the radical quenching effect of and gas dilution effects.•The final PLA maintains high mechanical strength due to uniform dispersion of PPP and strong interfaces.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study introduces a novel approach using wood fiber/PLA composite microperforated panel (WFCMPP) for indoor sound absorption purposes. WFCMPP, comprising rubber tree chip-derived fibers and a ...polylactic acid (PLA) matrix, with the dimensions of the rubber tree chip-derived fibers ranging from 0.5 to 1 mm, demonstrated promising sound absorption coefficients comparable to other natural fiber composite microperforated panels. The maximum sound absorption coefficient was recorded at 0.989 with a resonance frequency of 1416 Hz when the wood fiber composition was 30 %. The study also investigates the impact of wood fiber composition on sound absorption, revealing a linear relationship between fiber content and both porosity and sound absorption. The peak sound absorption coefficient of WFCMPP remained almost identical at different air gap thicknesses, showcasing the versatility and effectiveness of the samples. Additionally, the performance remained robust even with variations in air gap size. Scanning electron microscope analysis confirms the irregular porous structure and complexity contributing to enhanced sound absorption. WFCMPP presents a sustainable and effective alternative for acoustic applications, combining sound absorption performance with environmental considerations.
Display omitted
•Microperforated panels (MPPs) were fabricated from wood fiber/PLA composite using conventional machining.•Sound absorption of wood fiber/PLA MPPs (WFCMPP) was measured using an impedance tube.•All samples showed excellent absorption, with coefficients exceeding 0.9 between 1,400 and 1,470 Hz.•Porosity and surface morphology analyses were conducted to verify the complex structure of WFCMPP.•WFCMPP’s sound absorption performance was comparable to other natural fiber-based MPPs.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
