Mechanical Properties Of Polylactic Acid Research Articles

Optimizing FDM process parameters: predictive insights through taguchi, regression, and neural networks

Fused deposition modelling (FDM) is a popular additive manufacturing process used for rapid prototyping and the production of complex geometries. Despite its popularity, FDM’s susceptibility to variations in numerous process parameters can significantly impact the quality, design, functionality, and mechanical properties of 3D printed parts. This study explores thirteen FDM process parameters and their influence on the mechanical properties of polylactic acid (PLA) polymer, encompassing surface roughness, warpage, tensile and bending strength, elongation at break, deformation, and microhardness. The optimum parameters were identified alongside key contributors by applying the Taguchi method, signal-to-noise ratios, and analysis of variances (ANOVA). Notably, specific FDM parameters significantly affect the surface profile, with layer thickness contributing 32.65% and fan speed contributing 8.59% to the observed variations. Similarly, warping values show notable influence from nozzle temperature (29.53%), wall thickness (16.74%), layer thickness (16.56%), and retraction distance (12.80%). Tensile strength is primarily determined by wall thickness (31.83%), followed by infill percentage (26.73%) and infill pattern (16.18%). Elongation at break predominantly correlates with wall thickness (44.82%), with a supplementary contribution from nozzle temperature (10.90%). Microhardness lacks a dominant parameter. Bending strength variations primarily arise from layer thickness (38%), wall thickness (37.6%), and infill percentage (9.17%). Deformation tendencies are influenced by layer thickness (19.20%), print speed (11.37%), wall thickness, and fan speed (10.9% each). The optimized dataset of FDM process parameters was then employed in two prediction models: multiple-regression and artificial neural network (ANN). Evaluation based on the correlation coefficient (R2) and root mean squared error (RMSE) indicates that the ANN model outperforms the multiple-regression approach. The results indicate that precise control of FDM parameters, coupled with ANN predictions, facilitates the fabrication of 3D printed parts with the desired mechanical characteristics.

Effects of a phosphorus-nitrogen containing DOPO derivative on the flame retardancy and mechanical properties of polylactic acid foamed materials

In this study, a phosphorus-nitrogen flame retardant (DOPO-DABP) was synthesized by 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 4,4′-diaminobenzophenone (DABP). Then, polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), ammonium polyphosphate (APP), DOPO-DABP, Joncryl ADR-4370F(ADR), azodicarbonamide (ADC) and nano-SiO2 were used as raw materials to prepare flame-retardant modified PLA foamed materials by hot pressing. The synergistic effect of APP and DOPO-DABP not only effectively improves the flame retardancy of PLA foamed material, but also promotes their mechanical properties. The experimental results showed that when APP/DOPO-DABP=10/10, the vertical combustion grade (UL-94) of the material reached the V-0 level, the limiting oxygen index (LOI) was 34.4 %. The tensile strength of the material was 25.35 MPa, bending strength was 32.14 MPa. The cell diameter of the material was reduced to 46.72 μm, and the cell density of the material was 2.25×106/cm3.

Micromechanical Dilution of PLA/PETG-Glass/Iron Nanocomposites: A More Efficient Molecular Dynamics Approach.

Polylactic acid (PLA) and poly(ethylene terephthalate glycol) (PETG) are popular thermoplastics used in additive manufacturing applications. The mechanical properties of PLA and PETG can be significantly improved by introducing fillers, such as glass and iron nanoparticles (NPs), into the polymer matrix. Molecular dynamics (MD) simulations with the reactive INTERFACE force field were used to predict the mechanical responses of neat PLA/PETG and PLA-glass/iron and PETG-glass/iron nanocomposites with relatively high loadings of glass/iron NPs. We found that the iron and glass NPs significantly increased the elastic moduli of the PLA matrix, while the PETG matrix exhibited modest increases in elastic moduli. This difference in reinforcement ability may be due to the slightly greater attraction between the glass/iron NP and PLA matrix. The NASA Multiscale Analysis Tool was used to predict the mechanical response across a range of volume percent glass/iron filler by using only the neat and highly loaded MD predictions as input. This provides a faster and more efficient approach than creating multiple MD models per volume percent per polymer/filler combination. To validate the micromechanics predictions, experimental samples incorporating hollow glass microspheres (MS) and carbonyl iron particles (CIP) into PLA/PETG were developed and tested for elastic modulus. The CIP produced a larger reinforcement in elastic modulus than the MS, with similar increases in elastic modulus between PLA/CIP and PETG/CIP at 7.77 vol % CIP. The micromechanics-based mechanical predictions compare excellently with the experimental values, validating the integrated micromechanical/MD simulation-based approach.

Impact of strain rate on mechanical properties of polylatic acid fabricated by fusion deposition modeling

AbstractThe primary objective of this research is to investigate the impact of strain rate on the mechanical properties of polylactic acid (PLA) fabricated through fused deposition modeling. PLA material was fabricated in a grid pattern with 75% infill density, a 0.16 mm layer height, and a ± 45° printing direction. This study specifically investigated tensile strength, flexural strength, and interlaminar strength with respect to varying crosshead speeds (1, 2, 3, 4, and 5 mm/min). The highest tensile strength noted was 40.13 MPa at a cross—head speed of 5 mm/min. Maximum elongation of 7.1% was noted on cross head velocity of 1 mm/min, and the maximum interlaminar strength reached 76.04 MPa at 4 mm/min. At a crosshead speed of 4 mm/min, the tensile strength measured was 38.36 MPa, which is a value close to the maximum result achieved in the tensile test. Interlaminar strength was notably higher at a crosshead speed of 4 mm/min, indicating a strong integrity of the printed layers. The values for elongation percentage and flexural strength were also moderate at a crosshead speed of 4 mm/min, which was 4.9% and 55 MPa, respectively. Therefore, crosshead speed of 4 mm/min appears to be an optimum factor for testing 3D printed PLA parts. This research sheds light on understanding the critical influence of strain rate in the mechanical performance of 3D printed PLA.

Enhanced Flame Retardancy, Ultraviolet Shielding, and Preserved Mechanical Properties of Polylactic Acid with Fully Biobased Multifunctional Additives by a Green Method

Enhanced Flame Retardancy, Ultraviolet Shielding, and Preserved Mechanical Properties of Polylactic Acid with Fully Biobased Multifunctional Additives by a Green Method

Influence of SiC Doping on the Mechanical, Electrical, and Optical Properties of 3D-Printed PLA

Additive manufacturing, also known as 3D printing or digital fabrication technology, is emerging as a fast-expanding technology for the fabrication of prototypes and products in a variety of applications. This is mainly due to the advantages of 3D printing including the ease of manufacturing, the use of reduced material quantities minimizing material waste, low-cost mass production as well as energy efficiency. Polylactic acid (PLA) is a natural thermoplastic polyester that is produced from renewable resources and is routinely used to produce 3D-printed structures. One important feature that makes PLA appealing is that its properties can be modulated by the inclusion of nano or microfillers. This is of special importance for 3D-printed triboelectric nanogenerators since it can enhance the performance of the devices. In this work we investigate the influence of SiC micron-sized particles on the mechanical, electrical, and optical properties of a PLA-SiC composite for potential application in triboelectric energy harvesting. Our result show that the ultimate tensile strength of the pure PLA and 1%-doped PLA decreases with the number of fatigue cycles but increases by about 10% when SiC doping increases to 2% and 3%, while the strain at max load was about 3% independent of doping and the effective hardness was increased reaching a plateau at about 2 wt% SiC, about 40% above the value for pure PLA. Our results show that the mechanical properties of PLA can be enhanced by the inclusion of SiC, depending on the concentration of SiC. In addition, the same behavior is observed for the dielectric constant of the composite material increases as the SiC concentration increases, while the optical properties of the resulting composite are strongly dependent on the concentration of SiC.

Brewing sustainability and strength: Biocomposite development through tea waste incorporation in polylactic acid

This study aims to enhance the mechanical properties of polylactic acid by incorporating black tea waste as an economical and sustainable additive capable of being recycled. The black tea waste, after the hot water color removal process, is milled to a fine and uniform powder size. The combination of these particles with polylactic acid is carried out using a twin-screw extruder. Specimens of pure polylactic acid and biocomposites containing 3 and 5 wt% black tea waste are manufactured using a hot press machine at a temperature of 200 °C. The filaments are also successfully extruded for three-dimensional printing purposes. Scanning electron microscopy images reveal that in the polylactic acid–3% tea biocomposite, the tea particles are appropriately dispersed within the polylactic acid matrix. The tensile test results indicate that biocomposite polylactic acid-3% tea has the highest mechanical properties, with a tensile strength of 67 MPa, demonstrating a 34% increase compared to polylactic acid. Furthermore, the biocomposite of polylactic acid–3% tea waste exhibits the best performance with a fracture energy of 2.5 kJ/m2 in the impact test. Hence, polylactic acid–3% tea biocomposite can be recommended as a suitable sustainable substitute. Finally, numerical simulations are performed on biocomposites containing double keyhole notches. This analysis is conducted to observe the behavior of biocomposite models with double keyhole notch under mixed-mode loading. The critical fracture load of the models is calculated using the strain energy density criterion. It is observed that an increase in the notch inclination angle and notch radius leads to a decrease in the fracture load in the models.

Design of Experiments to Compare the Mechanical Properties of Polylactic Acid Using Material Extrusion Three-Dimensional-Printing Thermal Parameters Based on a Cyber-Physical Production System.

The material extrusion 3D printing process known as fused deposition modeling (FDM) has recently gained relevance in the additive manufacturing industry for large-scale part production. However, improving the real-time monitoring of the process in terms of its mechanical properties remains important to extend the lifespan of numerous critical applications. To enhance the monitoring of mechanical properties during printing, it is necessary to understand the relationship between temperature profiles and ultimate tensile strength (UTS). This study uses a cyber-physical production system (CPPS) to analyze the impact of four key thermal parameters on the tensile properties of polylactic acid (PLA). Layer thickness, printing speed, and extrusion temperature are the most influential factors, while bed temperature has less impact. The Taguchi L-9 array and the full factorial design of experiments were implemented along with the deposited line's local fused temperature profile analysis. Furthermore, correlations between temperature profiles with the bonding strength during layer adhesion and part solidification can be stated. The results showed that layer thickness is the most important factor, followed by printing speed and extrusion temperature, with very close influence between each other. The lowest impact is attributed to bed temperature. In the experiments, the UTS values varied from 46.38 MPa to 56.19 MPa. This represents an increase in the UTS of around 17% from the same material and printing design conditions but different temperature profiles. Additionally, it was possible to observe that the influence of the parameter variations was not linear in terms of the UTS value or temperature profiles. For example, the increase in the UTS at the 0.6 mm layer thickness was around four times greater than the increase at 0.4 mm. Finally, even when it was found that an increase in the layer temperature led to an increase in the value of the UTS, for some of the parameters, it could be observed that it was not the main factor that caused the UTS to increase. From the monitoring conditions analyzed, it was concluded that the material requires an optimal thermal transition between deposition, adhesion, and layer solidification in order to result in part components with good mechanical properties. A tracking or monitoring system, such as the one designed, can serve as a potential tool for reducing the anisotropy in part production in 3D printing systems.

The Effect of Ultraviolet Radiation on Mechanical Properties of Fused Deposition Modeling 3D Printed Materials

This study investigates the influence of ultraviolet (UV) radiation on the mechanical properties of Fused Deposition Modeling (FDM) 3D printed materials, specifically polycarbonate (PC) and polylactic acid (PLA) specimens. The research involves conducting experiments on five test specimens of each material exposed to UV radiation and comparing their mechanical properties to those of five control specimens that remain unexposed. The results reveal a significant mean difference between the mechanical properties of the control and UV-exposed materials. UV radiation caused a decrease in tensile strength for the PC material, while the PLA material exhibited an increase in tensile strength. The impact of UV radiation on PLA was more substantial compared to PC. Flexural strength testing showed an enhancement in strength for the UV-treated materials, with UV treatment having a greater influence on the flexural strength of PLA compared to PC. The mechanical properties of PLA were more significantly impacted by UV radiation than those of PC. The study findings suggest that PC and PLA materials exhibit different responses to UV exposure, which may have implications for their practical applications. Further research is needed to fully understand the underlying mechanisms governing these divergent responses and to optimize the performance of each material under UV radiation.

Obtaining Cellulose Nanocrystals from Olive Tree Pruning Waste and Evaluation of Their Influence as a Reinforcement on Biocomposites

The objective of this work is to improve the mechanical properties of polylactic acid (PLA) by incorporating cellulose nanocrystals (CNC) previously obtained from a cellulose pulp extracted from olive tree pruning (OTP) waste. Composites were manufactured by melt processing and injection moulding to evaluate the effect of the introduction of CNC with conventional manufacturing methods. This OTP-cellulose pulp was subjected to a further purification process by bleaching, thus bringing the cellulose content up to 86.1%wt. This highly purified cellulose was hydrolysed with sulfuric acid to obtain CNCs with an average length of 267 nm and a degradation temperature of 300 °C. The CNCs obtained were used in different percentages (1, 3, and 5%wt.) as reinforcement in the manufacture of PLA-based composites. The effect of incorporating CNC into PLA matrix on the mechanical, water absorption, thermal, structural, and morphological properties was studied. Maximum tensile stress and Young’s modulus improved by 87 and 58%, respectively, by incorporating 3 and 5%wt. CNC. Charpy impact strength increased by 21% with 3%wt. These results were attributed to the good dispersion of CNCs in the matrix, which was corroborated by SEM images. Crystallinity index, glass transition, and melting temperatures were maintained.

What controls layer thickness effects on the mechanical properties of additive manufactured polymers

3D printed artefacts are becoming more common and the effect of printing parameters on their properties is key to their performance in applications. Although parameters like build orientation and raster direction are well-studied the effect of layer thickness (and its introduction of size effects into the properties of the material) is less well-known. This study determines the influence of layer thickness on the mechanical properties of polylactic acid (PLA), acrylonitrile butadiene styrene (ABS) and PETG (polyethlene terephtalate glycol) 3D printed specimens made with fused filament fabrication (FFF). Samples were printed with differing layer thickness and tensile tested according to ASTM D638. The study also found that when increasing the layer thickness the mechanical properties of the specimens for both ABS and PLA decreased. When it came to ultimate tensile strength, the effect of layer thickness on PLA was more significant than on ABS with PETG being in much less significant. The differences were attributed to differences in additive layer adhesion and the effect of the structure and defects introduced by the additive layer process.

Biodegradation behavior of acetylated lignin added polylactic acid under thermophilic composting conditions

Acetylated lignin (AL) can improve compatibility with commercial plastic polymers compared to existing lignin and can be used as an effective additive for eco-friendly biocomposites. For this reason, AL can be effectively incorporated into polylactic acid (PLA)-based biocomposites, but its biodegradation properties have not been investigated. In this study, biodegradation experiments were performed under mesophilic and thermophilic conditions to determine the effect of AL addition on the biodegradation characteristics of PLA-based biocomposites. As a result, the PLA-based biocomposite showed a faster biodegradation rate in a thermophilic composting environment, which is higher than the glass transition temperature of PLA, compared to a mesophilic environment. 16S rDNA sequencing results showed that differences in microbial communities depending on mesophilic and thermophilic environments strongly affected the biodegradation rate of lignin/PLA biocomposites. Importantly, the addition of AL can effectively delay the thermophilic biodegradation of PLA biocomposites. As a result of tracking the changes in physicochemical properties according to the biodegradation period in a thermophilic composting environment, the main biodegradation mechanism of AL/PLA biocomposite hydrolysis. It proceeded with cleavage of the PLA molecular chain, preferential biodegradation of the amorphous region, and additional biodegradation of the crystalline region. Above all, adding AL can be proposed as an effective additive because it can minimize the decline in the mechanical properties of PLA and delay the biodegradation rate more effectively compared to existing kraft lignin (KL).

Effects of hexa (ethyl lactate)-cyclotriphosphazene on flame retardancy and mechanical properties of polylactic acid

Using biobased additives to improve the performance of polylactide (PLA) is important for maintaining its sustainability. In this work, an eco-benign flame retardant HELCP was synthesized by reacting ethyl lactate with cyclotriphosphazene. The HELCP was used to modify the flame retardancy of PLA. A small amount of 5.0 wt% HELCP endows PLA with a UL-94 V0 rating and a limiting oxygen index of 25.3 vol%. The mechanical properties and transparency of PLA/HELCP blends is almost the same as neat PLA. Moreover, the molecular weight of PLA blends does not decrease but increase instead. The phosphazene group of HELCP plays an important role in gas phase and the plasticization of HELCP shows a certain melting-away effect which is the flame-retardant mode of action in this system. The ethyl lactate part of HELCP undergoes ester exchange reactions with PLA and improves the compatibility between PLA and HELCP. This work provides a novel method for preparing PLA blends with good flame retardancy and mechanical properties.

Melt extruded polylactic acid (PLA)/algae bio‐composites: Effect of grafting level and filler loading on thermal and mechanical properties

AbstractIn this study, the combined effect of algae loading and in‐house produced coupling agent on thermal and mechanical properties of polylactic acid (PLA) prepared by melt compounding were investigated. The PLA‐grafted with maleic anhydride (MA) (PLA‐g‐MA) was used as a coupling agent to improve the interfacial adhesion between PLA and algae. The extent of grafting level was confirmed with FTIR and direct titration method. The results demonstrated the dependence of thermal stability and tensile properties on the grafting level of MA, and also on the concentrations of algae. Thus, it could be deduced that combination of algae at low concentrations (5 and 10 wt%) and PLA‐g‐MA with high grafting level can significantly improve the thermal stability of PLA. High grafting level of MA, showed increase in thermal stability of PLA. On the other hand, at high grafting level, there was an improvement in tensile modulus of PLA. The morphological analysis indicated better adhesion between algae and PLA, in composites containing PLA‐g‐MA with high grafting level. Overall, PLA/algae composites with improved interfacial adhesion and thermal stability were successfully prepared, in the presence of PLA‐g‐MA with high grafting level.

Influence of 3D printing process parameters on the mechanical properties of polylactic acid (PLA) printed with fused filament fabrication: experimental and statistical analysis

Influence of 3D printing process parameters on the mechanical properties of polylactic acid (PLA) printed with fused filament fabrication: experimental and statistical analysis

Effect of epoxy chain extenders on molecular structure and properties of polylactic acid

AbstractIn this work, a novel functional polylactic acid (PLA) was prepared by melt blending using epoxy Joncryl ADR 4468 (ADR) as chain extender. The effects of the epoxy chain expander ADR on the molecular structure, crystallization properties, rheological properties, and mechanical properties of PLA were studied. Furthermore, the chain expansion mechanism was analyzed. It was found that the epoxy group of the epoxy chain extender reacted with the terminal hydroxyl and terminal carboxyl groups of PLA in the molten state, thus significantly increasing the molecular weight of PLA. Meanwhile, the weight average molecular weight of PLA increased by 42.51% when the maximum additional amount of epoxy chain extender was 1.2 wt%. The dynamic rheological experiments also confirmed that ADR can effectively improve the storage modulus, loss modulus and complex viscosity of PLA systems and the Cole‐Cole diagram reveals the branched structure of PLA chain expansion systems. The formation of this branched structure will destroy the regularity of the PLA chain, reduce the crystallization capacity of PLA, and increase the cold crystallization temperature of the PLA system. Through SEM and mechanical property tests, it is found that the addition of ADR makes the molecular chain form a micro‐crosslinked structure, thereby improving the tensile strength of PLA. Therefore, the molecular structure of PLA was effectively regulated and exhibited a promising performance, which greatly expands the potential applications of PLA.

The Effects of Self-Polymerized Polydopamine Coating on Mechanical Properties of Polylactic Acid (PLA)-Kenaf Fiber (KF) in Fused Deposition Modeling (FDM).

This research examines the impact of self-polymerized polydopamine (PDA) coating on the mechanical properties and microstructural behavior of polylactic acid (PLA)/kenaf fiber (KF) composites in fused deposition modeling (FDM). A biodegradable FDM model of natural fiber-reinforced composite (NFRC) filaments, coated with dopamine and reinforced with 5 to 20 wt.% bast kenaf fibers, was developed for 3D printing applications. Tensile, compression, and flexural test specimens were 3D printed, and the influence of kenaf fiber content on their mechanical properties was assessed. A comprehensive characterization of the blended pellets and printed composite materials was performed, encompassing chemical, physical, and microscopic analyses. The results demonstrate that the self-polymerized polydopamine coating acted as a coupling agent, enhancing the interfacial adhesion between kenaf fibers and the PLA matrix and leading to improved mechanical properties. An increase in density and porosity was observed in the FDM specimens of the PLA-PDA-KF composites, proportional to their kenaf fiber content. The enhanced bonding between kenaf fiber particles and the PLA matrix contributed to an increase of up to 13.4% for tensile and 15.3% for flexural in the Young's modulus of PLA-PDA-KF composites and an increase of up to 30% in compressive stress. The incorporation of polydopamine as a coupling agent in the FDM filament composite led to an improvement in tensile, compressive, and flexural stresses and strain at break, surpassing that of pure PLA, while the reinforcement provided by kenaf fibers was enhanced more by delayed crack growth, resulting in a higher strain at break. The self-polymerized polydopamine coatings exhibit remarkable mechanical properties, suggesting their potential as a sustainable material for diverse applications in FDM.

Recent advances in flame retardant and mechanical properties of polylactic acid: A review

The large-scale application of ecofriendly polymeric materials has become a key focus of scientific research with the trend toward sustainable development. Mechanical properties and fire safety are two critical considerations of biopolymers for large-scale applications. Polylactic acid (PLA) is a flammable, melt-drop carrying, and strong but brittle polymer. Hence, it is essential to achieve both flame retardancy and mechanical enhancement to improve safety and broaden its application. This study reviews the recent research on the flame retardant functionalization and mechanical reinforcement of PLA. It classifies PLA according to the type of the flame retardant strategy employed, such as surface-modified fibers, modified nano/micro fillers, small-molecule and macromolecular flame retardants, flame retardants with fibers or polymers, and chain extension or crosslinking with other flame retardants. The functionalization strategies and main parameters of the modified PLA systems are summarized and analyzed. This study summarizes the latest advances in the fields of flame retardancy and mechanical reinforcement of PLA.

Effects of self‐assembled nucleating agent on the crystallization behavior, thermal properties, and mechanical properties of polylactic acid

AbstractPolylactic acid (PLA) is a biodegradable polyester, but its low crystallization rate and excessive embrittlement limit its application. Decanedioic acid 1,10‐bis (2‐benzoylhydrazide) (TMC‐300) as an effective nucleating agent of PLA will induce PLA epitaxial crystallization and improve the crystallization rate of PLA. This article studied the promoting behavior of TMC‐300 with different contents in composite systems on PLA crystallization. The results showed that with the increase of TMC‐300 content, the crystallinity can be significantly increased, up to 22 times, and t1/2 significantly decreases. Meanwhile, with the addition of TMC‐300, the typical spherical crystal morphology of PLA gradually became attached to TMC‐300 fibrous crystal morphology. In terms of mechanical properties, the tensile strength reached its maximum at 0.5 wt% of TMC‐300 content, increasing from 60.60 MPa (PLA) to 74.59 MPa (0.5‐TMC‐300), an increase of 23.09%. At this time, due to the reduction in spherical crystal size, the elongation at break also increased significantly. However, the thermal stability of PLA composites deteriorated with the increase of nucleating agent content due to the low thermal decomposition temperature of TMC‐300 itself, and the Tmax decreased from 372°C (PLA) to 353°C (5‐TMC‐300), a decrease of 19°C.

Thermal, crystallization, and mechanical properties of polylactic acid (PLA)/poly(butylene succinate) (PBS) blends

Thermal, crystallization, and mechanical properties of polylactic acid (PLA)/poly(butylene succinate) (PBS) blends