Polylactic Acid Material Research Articles

Investigation of mechanical recycling effect on electromagnetic properties of polylactic acid (PLA) – nanoclay nanocomposites: Towards a valorization of recycled PLA nanocomposites

Virgin and recycled poly(lactic acid) (PLA) based nanocomposite materials were obtained and subjected to microstructural, thermal and mechanical analysis in view of fabricating efficient microwave absorbers. PLA was first exposed to artificial accelerated aging, next was mechanically recycled through grinding followed by reprocessing using melt extrusion and compression molding, resulting in recycled PLA samples (rPLA). Addition of organically modified montmorillonite (OMMT) as nanoclay was performed in a second melt extrusion process in order to obtain virgin and recycled PLA-OMMT nanocomposites. The impact of recycling process and presence of OMMT nanoclay in the host PLA matrix has been studied by FTIR, TGA and DSC, while the mechanical performance has been investigated by micro-hardness test. The dielectric properties were measured in the 26–40 GHz frequency range using a Vector Network Analyzer to assess the performance of virgin and recycled PLA and OMMT-PLA material as microwave absorbers. The FTIR results show that the recycling process generated more C = O groups in the polymer. These polar groups tend to orient themselves in the direction of the applied field and increase the dielectric constant (ε'). Measured electromagnetic absorption index revealed that rPLA-4OMMT with a thickness of 400 µm is able to absorb 20.3% on average of the spectrum with a peak of 36%, while 200 µm-thick films of rPLA-4 wt.% OMMT has a mean absorption index of 14.5%. The overall results show that mechanically recycled polymer can replace virgin polymer in this kind of applications.

Effect of an Anaerobic Fermentation Process on 3D-Printed PLA Materials of a Biogas-Generating Reactor.

3D-printed materials are present in numerous applications, from medicine to engineering. The aim of this study is to assess their suitability for an application of interest today, that of testing of 3D-printed polylactic acid (PLA)-based reactors for biogas production using anaerobic digestion. The impact of temperature, pH, and aqueous phase on the tested bioreactor is investigated, together with the effect of the gaseous phase (i.e., produced biogas). Two batches of materials used separately, one after another inside the bioreactor were considered, in a realistic situation. Two essential parameters inside the reactor (i.e., pH and temperature) were continuously monitored during a time interval of 25 to 30 days for each of the two biogas-generating processes. To understand the impact of these processes on the walls of the bioreactor, samples of 3D-printed material were placed at three levels: at the top (i.e., outside the substrate), in the middle, and at the bottom of the bioreactor. The samples were analyzed using a non-destructive imaging method, Optical Coherence Tomography (OCT). An in-house developed swept-source (SS) OCT system, master-slave (MS) enhanced, operating at a central wavelength of 1310 nm was utilized. The 3D OCT images related to the degradation level of the material of the PLA samples were validated using Scanning Electron Microscopy (SEM). The differences between the impact of the substrate on samples situated at the three considered levels inside the reactor were determined and analyzed using their OCT B-scans (optical cross-section images). Thus, the impact of the biogas-generating process on the interior of the bioreactor was demonstrated and quantified, as well as the capability of OCT to perform such assessments. Therefore, future work may target OCT for in situ investigations of such bioreactors.

Regression Model for Optimization and Prediction of Tensile Strength of a PLA Prototype Printed

The experimental studies on prototypes printed in 3D with polylactic acid (PLA) material still seek to characterize the mechanical behavior and the deformations of these printed samples according to the various solicitations. The huge number of parameters intervening in these properties makes the control of process difficult and expensive. Previous studies on the impact of these parameters on the mechanical properties are limited to the investigation of a very less number of parameters. The objective of the present study is to take advantage of artificial intelligence tools, and to exploit the experimental results, in order to present artificial models that are able to optimize the choice of parameters intervening in the properties (tensile strength) of printed parts.

Effect of Infill Density in FDM 3D Printing on Low-Cycle Stress of Bamboo-Filled PLA-Based Material.

In this paper, the fatigue behavior of polylactic acid (PLA) material with bamboo filler printed by 3D additive printing using fused deposition modelling (FDM) technology at different infill densities and print nozzle diameters is investigated. The mechanical test results are supported by the findings from SEM image analysis. The fatigue behavior was tested at four consecutive 250 cycles at loads ranging from 5 to 20, 30, 40, and 50% based on the limits found in the static tensile test. The results of the static tensile and low-cycle fatigue tests confirmed significant effects of infill density of 60%, 80%, and 100% on the tensile strength of the tested specimens. In particular, the research results show a significant effect of infill density on the fatigue properties of the tested materials. The influence of cyclic tests resulted in the strengthening of the tested material, and at the same time, its viscoelastic behavior was manifested. SEM analysis of the fracture surface confirmed a good interaction between the PLA matrix and the bamboo-based filler using nozzle diameters of 0.4 and 0.6 mm and infill densities of 60%, 80%, and 100%. Low-cycle testing showed no reductions in the mechanical properties and fatigue lives of the 3D printed samples.

Supramolecular engineered ultrathin MXene towards fire safe polylactic acid composites

The combustion of polymeric materials will generate a mass of heat and release poisonous fumes, which not only hinders the personnel escape and causes casualties, but also causes the environmental contamination. Herein, a novel N–P–Co-containing supramolecular assembly network (MHCSN) flame retardant was synthesized by electrostatic interaction and supramolecular self-assembly technology. Then, MHCSN-Ti3C2Tx (MHCSN-TC) hybrids were synthesized by hydrogen bonding induced assembly and compounded with silicone wrapped ammonium polyphosphate (SiAPP) to successfully fabricate polylactic acid (PLA)/MHCSN-TC/SiAPP composites. PLA/MHCSN-TC/SiAPP composites exhibited the improved flame retardancy. For example, the introduction of 1.0 wt% MHCSN-TC and 14.0 wt% SiAPP into PLA resulted in significant reduction in the total heat release (50.1%), peak of heat release rate (64.1%) and peak of smoke production rate (61.3%). The improvements in flame retardance and smoke suppression of the PLA composites were due to the catalytic carbonization and barrier effect of the modified Ti3C2Tx nanoflakes. Meanwhile, the generated phosphorus-containing radicals generated by SiAPP captured the H• and HO• produced from the PLA material, and these phosphorus-containing species evolved into compact expanded char layers. This work offers a simple method to prepare highly effective flame retardants for PLA.

Effects of raster angle in single- and multi-oriented layers for the production of polyetherimide (PEI/ULTEM 1010) parts with fused deposition modelling

Abstract Material type and part deposition orientation are two important concerns in additive manufacturing. Additive manufacturing methods utilized by the industry are generally based on polylactic acid (PLA) or acrylonitrile butadiene styrene (ABS) materials using the fused deposition modelling (FDM) method. However, in present commercial applications, besides extensive use of PLA/ABS, their low strength has emerged as their biggest disadvantage. However, polyetherimide (PEI)/ULTEM 1010 parts represent high-performance engineering thermoplastics and offer superior mechanical properties with high thermal stability. On the other hand, selection of an appropriate raster angle orientation for single- and multi-oriented layers is also of considerable interest. A comprehensive study has been conducted herein on the building of a part using the FDM method using PEI/ULTEM 1010, and attempts have been made to identify the effects of raster angle in single- (0°, 30°, 45°, 60°, 90°) and multi-oriented (0/90°, 30°/−60°, 45°/−45°, 0°/90°/45°/−45°) layers. PEI specimens were manufactured via 3D printer, and the mechanical behaviour (tensile, bending and hardness) of the printed parts was correlated with their structures. Morphological properties of tensile fracture surface of 3D printed samples were analysed using scanning electron microscopy (SEM). Analysis indicated that a 0° part deposition orientation offers optimal mechanical properties because of the bonding structure.

Compression Strength Characteristics of ABS and PLA Materials Affected by Layer Thickness on FDM

This study aims to determine the compression strength of the Fused Deposition Material (FDM) additive manufacturing with the parameters in different layer thicknesses between 0.10 – 0.35 mm. The specimen manufacturing process refers to ASTM D695 Standards with ABS (acrylonitrile butadiene styrene) and PLA (polylactic acid) materials. Based on the test results, the highest compression strength is found in 0.15 mm layer thickness PLA material with a yield strength value of 66.78 MPa. The lowest compression strength is found in 0.35 mm of layer thickness ABS material with a yield strength value of 33.41 MPa. The value of compression strength on ABS and PLA materials varies with each layer thickness change.

The Effect of Layer Thickness on Impact Strength Characteristics of ABS and PLA Materials

This study aims to determine the impact strength of the Fused Deposition Material (FDM) additive manufacturing with the parameters in different layer thicknesses between 0.10 – 0.30 mm. The specimen manufacturing process refers to ASTM D256 Standards with ABS (acrylonitrile butadiene styrene) and PLA (polylactic acid) materials. Based on the test results, ABS specimens with a layer thickness of 0.10 mm had the largest impact strength with 0.078 J/mm2, while the smallest impact strength was found in PLA specimens with a layer thickness of 0.20 mm and 0.30 mm with an impact strength of 0.047 J/mm2. The value of impact strength on ABS and PLA materials varies with each layer thickness change.

Material Extrusion Additive Manufacturing of Poly(Lactic Acid): Influence of infill orientation angle

The effect that the infill orientation angle has on the strain-rate dependence of the yield stress for material extrusion additive manufactured (ME-AM) PolyLactic Acid (PLA) material was investigated. Symmetric angle-ply stacking sequences were used to produce ME-AM tensile test samples. Measured yield stresses were compensated for the voided structure, typical of ME-AM components. Furthermore, molecular orientation and stretch was macroscopically assessed by a thermal shrinkage procedure. Additionally, hot-press compression molded ( CM ) samples were manufactured and mechanically characterized in uniaxial tensile and compression in order to determine the material’s isotropic bulk properties. Initial model parameters for the Ree–Eyring modification of the Eyring flow rule were determined using CM data. According to SEM fractography, all samples showed microscopically brittle fracture behavior. Notwithstanding, contrary to CM samples, ME-AM specimens showed macroscopically ductile stress–strain behavior and a transition from a regime with only a primary α -deformation process, at low strain rates, to a regime with 2 deformation processes ( α + β ), at high strain rates. These effects are an influence of the processing step and are attributed to the molecular orientation and stretch of the polymer chains, provoking anisotropic mechanical properties. As a consequence, a deformation-induced change of the Eyring rate constants is needed to adequately describe the strain-rate dependence of the ME-AM yield stress behavior, leaving the initial activation volumes unchanged. Taking this deformation-dependence of the rate constants into account, yield stresses as a function of infill orientation angle can be appropriately predicted. • ME-AM samples with different symmetric angle-ply stacking sequences were produced. • PLA shows anisotropy in yield stress and strain-rate dependent behavior. • ME-AM samples show ductile stress–strain behavior, due to molecular orientation. • ME-AM samples show transition in strain-rate dependence, due to molecular orientation. • PLA demonstrates deformation-dependent Eyring rate constants.

Parametric Optimization of 3D Printing Process

Abstract: The term “three-dimensional printing” refers to a variety of manufacturing processes used to create a variety of things. Nine identically sized models were created utilising a low-cost 3D printer and polylactic acid (PLA) material using the design of experiments approach (DOE). Infill %, Layer thickness, and Nozzle diameter were the three input parameters that were examined, each of which had three levels. The ideal polylactic acid impact resistance (PLA). Through compressive testing, this study’s goal is to comprehend mechanical characteristics, economic benefits, and environmental advantages. The study’s findings will offer a thorough mechanical inventory for product design and production. This study also points to potential improvements in infill pattern design for additive manufacturing.

Production of compression and flexural test samples in 3D printer with PLA polymeric biomaterial and bone compression with appropriate properties

In this study, it is planned to design and develop a structure close to the real bone strength properties by using PLA (polylactic acid) material. 3D printers have started to take place in our daily lives with today's developing technology and are preferred because of their ease of production and low cost. It has been determined that the PLA biomaterial can be used as a bone substitute in the body. The samples produced have different filling ratios and different internal structures. In the study, the effects of changes in the internal structure on the mechanical properties were investigated. Bone geometry is considered as an important factor among the parameters affecting biomechanical properties. In order to determine the mechanical properties of PLA filament material, bending and compression samples were prepared as 3 pieces for each test. The aim of this study is to determine whether it can be used as bone in the body by measuring the mechanical properties of biocompatible PLA polymer material. In the current work, the quality of the 3d printer and the material used in production directly affects the mechanical properties. In bones in the human body, trabecular bone has 80% porosity and cortical bone 10% infill. In this study, it was tried to obtain structures with properties close to real bone strength by using test specimens with different infill rates. It has been determined from the obtained data that PLA polymer material can be developed and meet the mechanical values in bone.

Computational analysis of designing an improved coronary stents of biodegradable Poly-lactic Acid (PLA)

ABSTRACT The complications arising after the transplantation of conventional stents put atherosclerotic cardiovascular patients at high risk. Biodegradable poly-lactic acid (PLA) stents provide practical solutions for diseased vessels (atherosclerotic) and avoid the side complications of vessels and their incompatibility with permanent stents in the long term. PLA is a biodegradable and reliable material that is used for biodegradable stents designs to maintain natural mechanical behaviour in blood vessels. In this study, we suggest a new cross section ‘circular and elliptic’ that are proposed based on basic square shape cross section to study the mechanical behaviour of stents under pulsatile blood pressure in the blood vessels in order to choose the best shape to allow the biodegradability of Absorb stents with Poly-lactic Acid (PLA) material by numerical fatigue study. Three types of cross-sections stents struts have been analysed to compare their mechanical properties in terms of stress, strain, fatigue damage and life cycle. The numerical results obtained from the finite element analysis (FEA) method demonstrate that the elliptical and circular stents design has better efficiency in terms of stress and strain (16.66–33.33%) and fatigue damage (62.4–86.07%) compared to the square design.

3D printed laboratory equipment to measure bulk materials in extreme conditions

Due to relatively new solutions in the field of 3D printing, there are few studies on the possibility of using printed elements in measuring devices. The aim of this study was to investigate the possibility of using instruments made by material extrusion 3D printing method for measurement of selected mechanical-physical properties of bulk materials. Study explores the feasibility of measuring bulk material mechanical-physical properties when there are obstacles for printing original or modified measuring instruments in common practice. To achieve the goals a series of experiments such as Schulze’s ring shear tests, Freeman’s FT4 shear tests, compressibility tests, and Flow Rate and Stability tests were performed with use of original aluminium or steel made instruments and 3D printed instruments from polylactic acid and acrylic styrene acrylonitrile materials, using lunar regolith simulants LHS-1 and LMS-1 produced by CLASS Exolith Lab as a sample material. The results obtained from tests with original and printed instruments were then compared. The compared values of tests showed applicability of the 3D printed measuring instruments in a 5% range of measurement deviation. The biggest advantages of the 3D printed measuring instruments were the lower weight, the ability to print on the spot, to replace a damaged part with a new 3D printed part on-demand if extremely fast results are needed or due to the logistical unavailability, customization of the standardized tests for better understanding the behaviour of the particulate materials, and cheaper manufacturing costs.

Study of Material Color Influences on Mechanical Characteristics of Fused Deposition Modeling Parts.

The objective of the present work is to evaluate the influence of material color on mechanical properties of fused deposition modeling (FDM) parts. The performance of the products is evaluated by testing eight different colors of acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) material in terms of tensile strength, compressive strength, and flexural strength. The analysis of data shows a significant difference in mechanical characteristics of prints depending on filament color. For different colors, these three strengths almost follow the same rising and falling tendency. In order to explore the relationship between mechanical strengths and filament colors, the color-mixing theory and the least-squares method are adopted to fit the best ratio coefficients of different color combinations. Results are presented showing that the strength value (e.g., tensile) of the mixed color can be evaluated through that of primary colors by fitting the other strength (e.g., compressive or flexural). It is shown that the predicted value is always no more than 7% error compared with the actual strength, in spite of two-color or three-color mixtures. An additional confirmation test with seven colored PLA filaments from different suppliers was conducted to focus on the extensibility. The outcomes show the maximum fitting errors of strengths for mixed colors in all cases are within 5%, proving the effectiveness and applicability of this predicted approach. This study can bring a detailed analysis that enables better estimation of the function of material color and contributes to improving the property of FDM printed products for consumers by choosing the suitable filament color.

Performance Analysis of PLA Material Based Micro-Turbines for Low Wind Speed Applications.

Various studies have been conducted in recent years to find solutions to the issues in wind energy conversion systems. A 100W horizontal axis micro wind turbine is built for low wind speed applications in this work. The Blade Element Momentum theory approach was used to design the 100W micro wind turbine blade. The wind turbine blade 3D model was created using the CREO CAD 3.0 software. Based on the aerodynamic studies, the airfoil S9000 is chosen among others for generating high power at low wind speed. The density, Young’s modulus, and the Poisson ratio of the proposed wind turbine blade model with acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) materials were compared. ABS and PLA materials were investigated using a 0.33 mm layer of infill ranging from 10% to 100%. PLA and ABS output values were compared in terms of deformation, equivalent stress, and equivalent strain. PLA materials, on the other hand, have less deformation and greater structural properties than ABS materials. The wind blade structural analysis was performed in ANSYS 15 software, and the details of experimental and simulated results are presented in this paper.

Biocompatible Nanomaterials for Burns.

The skin being the largest organ, protects our body against harmful chemicals, pathogens, and physical agents. It constitutes primarily three layers: epidermis, dermis, and subcutaneous layers. Injuries occurring due to burning remain localized to the skin or other organic tissues caused by flame, extreme heat, and close contact with chemicals or heated objects. Conventional treatments are available for the treatment of burns; however, they are expensive and might completely replace autologous tissue transfer. Nanotechnology-based approaches include organic nanoparticles, dendrimers, hydrogels, etc. Biocompatibility usually refers to the ability of biomaterials to perform their respective functions centered on medical therapy without causing any systemic or local effects. Polymeric materials like a natural (chitosan and hyaluronic acid) and synthetic (polylactic acid and polycaprolactone) materials are employed as biomaterials. Various preclinical and clinical studies were performed in animal models. In this review, the authors have discussed elaborately the biocompatible polymers, which are used in the treatment of burn wounds. Afterwards, a brief discussion on the polymers, pre-clinical and clinical studies, and regulatory concerns related to nanomaterials have also been covered.

Redesign of a Metallic Component Using Polylactic Acid – PLA by Fused Deposition Modeling – FDM for Durability Increase

AbstractThe term “3D printing” can refer to a variety of processes where material is deposited, joined, or solidified under computer control to create a three‐dimensional (3D) object. According to this principle, the material is added (such as fluid molecules or powder grains being fused together), typically layer by layer. One of the key advantages of 3D printing is the ability to produce very complex shapes or geometries, from the simplest to the most complex, that will be otherwise impossible to construct by hand, including hollow parts or parts with internal truss structures to reduce weight. In industries and companies where 3D printing is still a relatively new addition, the polylactic acid (PLA) material is the best option, because it is known in the industry as the easiest filament material to print. It is ideal for those who are looking to carry out fast prototyping, therefore it is the perfect choice for quick work. In this article, the authors intend to establish a set of printing rules for a geometric shape made of polymeric material (PLA) through the 3D printing process for a practical application and to present as much as possible the behavior in time of this printed component that replaces a non‐corrosive metal component.

The development and characterization of carbon nanofiber/polylactic acid filament for additively manufactured piezoresistive sensors

In this work, an investigation into the effects of manufacturing parameters on carbon nanofiber (CNF)/polylactic acid (PLA) filament for fused filament fabrication (FFF) additive manufacturing (AM)-produced strain sensors was conducted. A design of experiments (DOE) approach was undertaken to explore the impact of CNF weight fraction, extrusion temperature, and number of extrusions on sensor performance. The initial extrusion combined pulverized PLA material and CNFs via a dry melt-mixing process. Through the DOE process, it was found that extruding CNF/PLA material at 185 °C for two total extrusions yielded material with dramatic improvements in electrical properties compared to unmodified material. Using the optimal manufacturing procedure, piezoresistive dog-bone shaped sensors were manufactured via FFF with 5.0, 7.5, and 10.0 wt % CNF/PLA filament and three different sizes. Piezoresistive testing under monotonic and cyclic loading conditions revealed strong and repeatable behavior from the piezoresistive AM sensors produced with 7.5 and 10.0 wt % CNFs. In general, 7.5 wt % CNF/PLA sensors showed greater strain sensitivity than 10.0 wt % CNF/PLA sensors for monotonic loading. Additionally, sensor size appeared to contribute significantly to the performance of 7.5 wt % CNF/PLA sensors. However, the 10.0 wt % CNF/PLA sensors exhibited greater repeatability in their piezoresistive response, and sensor size had much less impact on strain sensing performance. The printed sensors also exhibited a strong response under cyclic loading, however, variability in their piezoresistive response was significantly higher than under monotonic loading conditions. The results of this study are an important step towards the realization of low-cost, easily produced, and highly customizable strain sensors produced via FFF technology.

Steering of flexural wave propagation in tunable magnetorheological elastomers metasurface by modulating magnetic field

Metasurfaces have remarkable power for steering flexural waves, and most of the existing studies for phase modulation of the metasurface concentrate on changing the geometrical parameters of the structure. However, when the external conditions change, these parameters cannot be adjusted in real-time, which is not convenient for engineering applications. Therefore, in this paper, a tunable magnetorheological elastomers (MREs) metasurface composed of MREs and three-dimensional (3D) printing material polylactic acid (PLA) is proposed to steer the propagation of incident flexural waves arbitrarily. The phase shift in a full 2π span can be achieved by manipulating the applied magnetic field to tune the modulus of the MREs. Then, based on the Generalized Snell's Law, MREs metasurfaces with different refraction angles are designed by adjusting the applied magnetic field, including positive refraction and negative refraction. In addition, wave focusing and self-bending beam effects are also investigated. Different focal spots and self-bending beam paths can be realized by adjusting the applied magnetic field. Finally, a sample of the tunable MREs metasurface is fabricated by 3D printing technology composed of host plate and MREs units to demonstrate the focusing effect experimentally. The results show that the designed tunable MREs metasurface only requires a small magnetic field to achieve deflecting of the flexural waves (the maximum magnetic field is 66.93 mT), which is easy to implement in practical engineering. The simulated and experimental results of the elastic wave focusing effect are in good agreement. The proposed metasurface provides a guiding design for elastic wave modulation.

The Effect of Infill Pattern on Tensile Strength of PLA Material in Fused Deposition Modeling (FDM) Process

Fused deposition modeling (FDM) is an additive manufacturing (AM) process often used to build geometrically complex prototypes and parts. It is becoming more popular since it improves products by eliminating the need for high-priced equipment. Materials, printing methods, and printing variables all impact the mechanical characteristics of printed items. The process parameters of FDM affect the parts' quality and functionality. This study examines the influence of different infill patterns on test specimens made of polylactic acid (PLA) tensile strength. Total of 10 different infill patterns (IPs): Grid, Lines, Triangles, Tri-Hexagon, Cubic, Gyroid, Zig-zag, Concentric, Octet, and Cubic subdivision were taken as process variables. Samples were printed using processing parameters (speed 60 mm/s, layer height 0.1 mm, infill density 80%, extruded at 200◦C). The ASTM D638 tensile test was used to determine the tensile strength based on this printing parameter. According to tensile test results, the infill pattern significantly affects the tensile strength. The results showed that the concentric infill pattern has a higher tensile strength of 32.174 MPa, whereas the triangles infill pattern has a lower tensile strength of 20.934 MPa.