Plasticized PLA Research Articles

Constrained amorphous interphase in plasticized poly(lactic acid): Composition and tensile elastic modulus estimation

The study investigates the distribution of the plasticizers acetyl triethyl citrate (ATEC) and acetyl tributyl citrate (ATBC) in the mobile amorphous (MAF) and rigid amorphous (RAF) fractions of semi-crystalline plasticized poly (lactic acid) (PLA) containing 5 wt% of plasticizer. During crystallization, the ATEC and ATBC concentration in the MAF increases from 5 to about 8 wt%. At the end of crystallization, the plasticizers concentration in the RAF is lower than that in the MAF. The progressive decrease of the ATEC and ATBC concentration in the RAF region could be linked to the growth of subsidiary lamellae in more restricted amorphous areas. The study also introduces an estimation of the tensile elastic modulus of the RAF (ERAF) in semi-crystalline pure and plasticized PLA containing α-crystals. The mechanical model with crystalline lamellae perpendicular to the stress direction turned out to be the most appropriate arrangement to represent the morphological organization in PLA samples prepared by injection-moulding processing at high pressure. The mathematical procedure led to a crystal elastic modulus (EC) of the α-phase in excellent agreement with the theoretical value reported in the literature (EC = 14 GPa), and to an ERAF value around 5.5 GPa, for both pure and plasticized PLA, thus suggesting that both ATEC and ATBC do not exert plasticizing action on the RAF.

Design and development of latex cup collector robot

Global rubber production has declined over the past few years as a result of a number of variables, including both environmental and human factors. In this paper, an automated robot prototype that collects latex cups was developed to improve global rubber production by assisting workers in rubber plantations. The robot was built on a mobile platform with a motorized Five Degrees of Freedom (DoF) robotic arm, Ackermann steering, double wishbone suspension, rear-wheel drive and a latex storage tank to store the latex collected from the trees. The robot was equipped with ultrasonic sensors and a camera module to locate latex cups and rubber trees so that it could move and perform tasks accurately. In addition, encoder sensor modules were used to improve the accuracy of the movements by measuring the rotational speed of the motors. The yield strength of the PLA plastic material used in developing the latex cup collector robot is 7.00 x 107N/m2 and the maximum stress of the critical parts should not exceed the maximum yield strength of the PLA plastic. In mobility test, the robot is able to travel through obstacles of 10mm and 15mm height. The topple angle of the robot in the balancing test is greater than 37°, ensuring the stability of the robot.

Utilizing EEG Signal Data and Motion to Aid in Prosthetic Hand Motion

Current prosthetic arm technologies are often difficult to use intuitively by amputees, require invasive surgical procedures, and can be extremely costly with prices ranging from $20,000 to $80,000. To address these challenges, the engineering goal of this project aims to design a smart, low-cost, mind-controlled transhumeral prosthesis by integrating the brain-interfacing capabilities of electroencephalography (EEG), the economical means of 3D printing technology, and gesture-detecting attributes of an accelerometer-gyroscope. Single-channel brain signals are transmitted through Bluetooth to be interpreted by a novel EEG decoding algorithm and head gestures from the inertial measurement unit actuate movement within the arm. Force sensitive resistors were employed to regulate force control in real-time to optimize grasp type. An LCD screen is integrated within the arm’s design to display the type of touch it is exerting on an object. The arm itself was printed with an original design utilizing PLA plastic filament making it extremely durable and lightweight. After thoroughly testing the prosthesis, the novel EEG decoding system boasts an accuracy of 94.7% and a user cognition to machine delay of 1.64 + - 0.37 seconds. The inertial measurement unit system recognizes user gestures with a delay of .136 seconds. With a bill of materials approximately $375 USD and ability to be moved in 4 degrees of motion, this novel upper limb prosthesis serves as a promising alternative to existing units on the market. The algorithms developed within this project have a wide range of use within other brain control interface projects.

Analysis of Printing Parameters for Sheet Metal Bending with FDM Printed Tools

The objective of this work is to use PLA plastic matrices printed using the FDM additive manufacturing technique as an alternative to conventional sheet metal bending. In this way, the demand of the industry to obtain highly customized short series bent parts at a reduced price is covered. To demonstrate this hypothesis, first, the maximum compressive strength of FDM printed specimens with different manufacturing parameters was characterized by performing a parametric analysis using a factorial design of experiments (DOE) model and based on the ISO 604 standard. Once the results were analysed, an articulated bending tool was designed and printed with the best configuration obtained previously. Then, 50 S280GD galvanized steel sheets of 1 mm thickness were bent. Finally, the bending angles of the sheets were examined, checking that the bending was performed correctly, obtaining the desired shape in the sheet. As for the analysis of the economic impact, a 97.75% reduction in the manufacturing price of the tooling with respect to conventional tooling was observed, demonstrating the viability of these dies in an industrial environment.

Analysis of elastic properties of 3D-printed parts using the finite element method

This research paper presents a comparative analysis of the elastic properties of 3D-printed parts made from polymer composite materials using PLA plastic. The analysis was conducted using both the finite element method and experimental measurements. Specifically, PLA-Cg+ and PLA-CCF samples were printed with varying printing parameters, such as raster angle and print layer thickness. The study demonstrates that the employed numerical calculation algorithm provides sufficiently accurate assessment of the elastic characteristics of materials across different combinations of the investigated parameters. Moreover, the analysis of the results reveals that the accuracy of the calculations is significantly influenced by the microstructure, which is determined by the size and shape of the pores that form during the printing process.

Prompt gamma ray activation analysis for determining chemical composition of 3D printing and casting materials used in biomedical applications.

Three-dimensional printing and casting materials were analyzed by prompt gamma-ray activation analysis (PGAA) to determine their suitability as human tissue surrogates for the fabrication of phantoms for medical imaging and radiation dosimetry applications. Measured elemental compositions and densities of five surrogate materials simulating soft tissue and bone were used to determine radiological properties (x-ray mass attenuation coefficient and electron stopping power). When compared with radiological properties of International Commission on Radiation Units and Measurements (ICRU) materials, it was determined that urethane rubber and PLA plastic yielded the best match for soft tissue, while silicone rubber and urethane resin best simulated the properties of bone.

Anaerobic digestion of commercial PLA and PBAT biodegradable plastic bags: Potential biogas production and 1H NMR and ATR-FTIR assessed biodegradation

Bioplastics aim to substitute conventional plastics in most applications, a critical one being the collection of organic wastes for composting or anaerobic degradation. The anaerobic biodegradability of six commercial bags composed of PBAT or PLA/PBAT blends and certified as compostable [1] was studied using 1H NMR and ATR-FTIR techniques. This study aims to elucidate if commercial bioplastic bags are biodegradable under conventional conditions found in anaerobic digestates. Results showed that all studied bags are hardly anaerobically biodegradable at mesophilic temperatures. The biogas yield resulting from the anaerobic digestion under laboratory conditions oscillated between 270.3 ± 45.5 L kgVS−1 for a trash bag composed of 26.64 ± 0.03%/73.36 ± 0.03% PLA/PBAT and 36.7 ± 25.0 L kgVS−1 for a bag composed of 21.24 ± 0.08%/78.76 ± 0.08% PLA/PBAT. The degree of biodegradation did not correlate with PLA/PBAT molar composition. However, 1H NMR characterization showed that the anaerobic biodegradation occurred mostly in the PLA fraction. No bioplastics biodegradation products were detected in the digestate fraction (<2 mm). Finally, none of the biodegraded bags comply with the EN 13432 standard.

Development of an anatomical breast phantom from polyvinyl chloride plastisol with lesions of various shape, elasticity and echogenicity for teaching ultrasound examination.

The WHO reported an increasing trend in the number of new cases of breast cancer, making it the most prevalent cancer in the world. This fact necessitates the availability of highly qualified ultrasonographers, which can be achieved by the widespread implementation of training phantoms. The goal of the present work is to develop and test an inexpensive, accessible, and reproducible technology for creating an anatomical breast phantom for practicing ultrasound diagnostic skills in grayscale and elastography imaging, as well as ultrasound-guided biopsy sampling. We used FDM 3D printer and PLA plastic for printing an anatomical breast mold. We made a phantom using a mixture of polyvinyl chloride plastisol, graphite powder, and metallic glitter to simulate soft tissues and lesions. Various degrees of elasticity were imparted using plastisols of stiffness ranging from 3 to 17 on the Shore scale. The lesions were shaped by hand. The materials and methods used are easily accessible and reproducible. Using the proposed technology, we have developed and tested a basic, differential, and elastographic versions of the breast phantom. The three versions of the phantom are anatomical and intended for use in medical education: the basic version is for practicing primary hand-eye coordination skills; the differential one is for practicing the differential diagnosis skills; the elastographic version helps developing the skills needed for assessing the stiffness of tissues. The proposed technology allows the creation of breast phantoms for practicing hand-eye coordination and develop the critical skills for navigation and assessment of the shape, margins, and size of the lesion, as well as performing an ultrasound-guided biopsy. It is cost-effective, reproducible, and easily implementable, and could be instrumental in generating ultrasonographers with crucial skills for accurate diagnosis of breast cancer, especially in low-resource settings.

Novel Epoxidized Brazil Nut Oil as a Promising Plasticizing Agent for PLA.

This work evaluates for the first time the potential of an environmentally friendly plasticizer derived from epoxidized Brazil nut oil (EBNO) for biopolymers, such as poly(lactic acid) (PLA). EBNO was used due to its high epoxy content, reaching an oxirane oxygen content of 4.22% after 8 h of epoxidation for a peroxide/oil ratio of 2:1. Melt extrusion was used to plasticize PLA formulations with different EBNO contents in the range of 0-10 phr. The effects of different amounts of EBNO in the PLA matrix were studied by performing mechanical, thermal, thermomechanical, and morphological characterizations. The tensile test demonstrated the feasibility of EBNO as a plasticizer for PLA by increasing the elongation at break by 70.9% for the plasticized PLA with 7.5 phr of EBNO content in comparison to the unplasticized PLA. The field-emission scanning electron microscopy (FESEM) of the fractured surfaces from the impact tests showed an increase in porosity and roughness in the areas with EBNO addition, which was characteristic of ductile failure. In addition, a disintegration test was performed, and no influence on the PLA biodegradation process was observed. The overall results demonstrate the ability of EBNO to compete with other commercial plasticizers in improving the ductile properties of PLA.

Development and Evaluation of the Properties of Active Films for High-Fat Fruit and Vegetable Packaging

β-cyclodextrin and allyl isothiocyanate inclusion complexes (β-CD:AITC) have been proposed for developing fresh fruit and vegetable packaging materials. Therefore, the aim of this research was to develop active materials based on poly(lactic acid) (PLA) loaded with β-CD:AITC and to assess changes in the material properties during the release of AITC to food simulants. PLA films with 0, 5 and 10 wt.% β-CD:AITC were developed by extrusion. Surface properties were determined from contact angle measurements. Films were immersed in water, aqueous and fatty simulants to assess the absorption capacity and the change in the thermal properties. Moreover, the release of AITC in both simulants was evaluated by UV-spectroscopy and kinetic parameters were determined by data modeling. Results showed that a higher concentration of β-CD:AITC increased the absorption of aqueous simulant of films, favoring the plasticization of PLA. However, the incorporation of β-CD:AITC also avoided the swelling of PLA in fatty simulant. These effects and complex relationships between the polymer, inclusion complexes and food simulant explained the non-systematic behavior in the diffusion coefficient. However, the lower partition coefficient and higher percentage of released AITC to the fatty simulant suggested the potential of these materials for high-fat fruit and vegetable active packaging applications.

Application of Composite Filament with the Addition of Metallic Powders in 3D Printing

The aim of this experimental research was to 3D-print a filament based on PLA plastic with a metallic powder. The filament contained approximately 80 – 90 % of copper powder. The base component of the filament is thermoplastic PLA, a polymer belonging to the group of aliphatic polyesters. Composites based on PLA and powders have different properties from traditional PLA filaments without admixtures. The created composite structure is intended for 3D printing with the FDM (Fused Deposition Modeling) technology, using rapid prototyping. The printed samples were subjected to the sintering process. The fractures of the sintered samples were SEM and EDS analyzed.

Development of removal modes of 3D-printed polymer patterns from ceramic molds

The use of additive technologies, particularly 3D printing, to make patterns instead of traditional wax patterns is promising for casting into ceramic molds. However, when using polymer patterns, there is a problem of cracking ceramic shells during their firing. The goal of the work was to develop optimal thermo-kinetic modes of removal of disposable plastic patterns from ceramic molds, which will prevent the formation of cracks in ceramics. During the study, samples of patterns made by 3D printing from various plastics were selected and examined. Laboratory tests were carried out on a batch of ceramic shells made of electrocorundum. The methods of removing plastic patterns from ceramic molds by means of two-stage firing in thermal furnaces were investigated. The low-temperature stage of firing consisted in gradually heating the ceramics up to 350 °C. During it, the material of the patterns was compacted, softened, melted, and partially gasified. This reduced uncontrolled gas pressure and stress in the ceramic and prevented the formation of cracks in it. The high-temperature firing phase (1000—1100 °С) was performed for sintering ceramics and removing the remains of plastic materials. The influence of different plastic materials on the quality of the casting mold was investigated. It is proposed to use PLA plastic for the 3D printing of patterns, as it meets the requirements of environmental friendliness and cost. The possibility of improving the surface quality of ceramic shells by coating them with a thin layer of wax-like material is also considered. According to the results of research on the surface of ceramic forms, it is proposed to add structural elements to plastic patterns that reduce deformations of ceramic forms during firing. The developed firing modes of the patterns are used in the production of ceramic molds for endoprostheses.

Properties of poly(lactic acid)/cellulose nanofiber biocomposites: Effect of polymeric plasticizers

Biodegradable composites from renewable resources have been of much interest in many industries. This work aims to develop a poly(lactic acid) (PLA)-based composite with a good balance of stiffness and impact strength by combined utilization of cellulose nanofiber (CNF) and polymeric plasticizer. The composites were prepared by a melt-compounding process. CNF, having diameters of approximately 10 nm and lengths of several microns, was extracted from wood sawdust and used without any surface modification. The effects of polymeric plasticizer selection on the thermal properties and mechanical performance of PLA and PLA/CNF composites were explored. Poly(butylene adipate) (PBA) as a polymeric plasticizer was compared with poly(ethylene glycol) (PEG) as a commonly used plasticizer for PLA. The reinforcement effect of CNF was evident, even at a low loading of 1 wt%. The composite mechanical properties could be efficiently tailored by properly selecting the plasticizers. The composites of high ductility (elongation > 400 %) were achieved using PEG plasticizer, whereas the composites containing PBA plasticizer exhibited relatively higher modulus, strength, and heat resistance. The plasticizers had strong effects not only on the mechanical performance but also on the crystallization behaviors of PLA.

Blending PLA with Polyesters Based on 2,5-Furan Dicarboxylic Acid: Evaluation of Physicochemical and Nanomechanical Properties

Poly(lactic acid) (PLA) is a readily available, compostable biobased polyester with high strength and toughness, and it is excellent for 3D printing applications. Polymer blending is an economic and easy way to improve its properties, such as its slow degradation and crystallization rates and its small elongation, and thus, make it more versatile. In this work, the effects of different 2,5-furan dicarboxylic acid (FDCA)-based polyesters on the physicochemical and mechanical properties of PLA were studied. Poly(butylene furan 2,5-dicarboxylate) (PBF) and its copolymers with poly(butylene adipate) (PBAd) were synthesized in various comonomer ratios and were blended with 70 wt% PLA using melt compounding. The thermal, morphological and mechanical properties of the blends are investigated. All blends were immiscible, and the presence of the dispersed phases improved the crystallization ability of PLA. Mechanical testing revealed the plasticization of PLA after blending, and a small but measurable mass loss after burying in soil for 7 months. Reactive blending was evaluated as a compatibilizer-free method to improve miscibility, and it was found that when the thermal stability of the blend components allowed it, some transesterification reactions occurred between the PLA matrix and the FDCA-based dispersed phase after 20 min at 250 °C.

Fate of petroleum-based and plant-based teabags exposed to environmental soil conditions for one year.

Petroleum-based plastics are materials which have provided important industrial benefits from being lightweight and having low production costs. However, plastic pollution is pervasive and ubiquitous on all environments. This has led some industries to rapidly introduce the so called ‘bioplastics’ into the market by switching the conventional ones for new plant-based alternatives with similar properties. However, little is known about the fate of such alternatives especially in the open environment. In this novel study, the degradation of teabags from eight different brands was investigated, five petroleum based (cellulose-PP blend) and three plant-based (cellulose, cellulose-PLA blend and PLA). The degradation was tested under real-environmental soil conditions over a 12-month period. Fourier Transform Infrared Spectroscopy (FTIR-ATR) and Scanning Electron Microscopy (SEM) techniques were used to examine the change in polymer makeup and surface degradation of teabags at 3 weeks, 3.5, 6 and 12 months. Teabag dry weight and any retrieved fragments were measured over time. Teabags that contained a plastic blended to cellulose were brittle or degraded into smaller fragments after 3 weeks in soil. Parallel to this, the cellulose layer also degraded in this short timeline. Petroleum-based teabags produced the highest numbers of PP fragments overtime and fragmented teabags were still found after 12 months. Plant-based teabags made of cellulose only or a blend of cellulose-PLA were absent from soil samples after 3.5 months, including no fragments. Contrary to this, teabags made of PLA which were marketed as completely biodegradable, persisted completely intact in soil throughout all time points. The novel results from this study provide a perspective on plastic degradation in terrestrial sources. Based on these findings, it can be recommended that teabags mostly made of cellulose or cellulose blended with a bioplastic present in a smaller ratio, are a better alternative to petroleum-based or pure PLA plastics, in terms of rapid environmental degradation. Further studies should focus on their ecotoxicity, additive presence, microbial degradation and life cycle in order to draw a full environmental assessment.

Comparison of Calculated and Experimental Depth Distributions of Gamma Radiation Doses in Polymer Media

The paper discusses a comparison of depth distributions of doses in plastics obtained by simulation in the PCLab software and experimentally with a Theratron Equinox–80 gamma–therapy unit. We used items made of ABS, HIPS and PLA plastics suitable for 3D printing and with different fill factors. Our study has demonstrated that the simulation results are consistent with the experimental ones within the uncertainty limits.

The influence of nucleating agents, plasticizers, and molding conditions on the properties of injection molded PLA products

Poly(lactic acid) (PLA) is a “green” alternative to petroleum-based plastics and a desirable choice for many applications. However, low heat deflection temperature and lack of toughness, together with the slow crystallization kinetic of neat PLA hinder its widespread application. The weak properties of PLA can be improved with the improvement of crystallinity, which depends on molecular weight, D-lactide content, the presence of different modifiers and the processing conditions. We aimed to maximize the crystallinity and crystallization rate of PLA to explore the limitations of PLA when it is processed by injection molding. Therefore, we selected PLA with low D-lactide content, the three effective nucleating agents and the two suitable plasticizers. We found that the heat deflection temperature, tensile strength, and Young’s modulus of PLA modified with nucleating agents were considerably better than those of Acrylonitrile Butadiene Styrene (ABS). However, the elongation at break of the annealed and the simultaneously nucleated and plasticized PLA compounds was significantly lower than that of ABS. The addition of nucleating agents and plasticizers and the variation of mold temperature did not improve the brittleness of PLA. The elongation at break of PLA was still very low and stayed in the 1.7–2.5% range.

Effect of the Addition of MgO Nanoparticles on the Thermally-Activated Shape Memory Behavior of Plasticized PLA Electrospun Fibers.

In this work, the thermally-activated shape memory behavior of poly(lactic acid)-based electrospun fibers (PLA-based efibers) reinforced with different amounts of magnesium oxide (MgO) nanoparticles (NPs) was studied at different temperatures. In particular, MgO NPs were added at different concentrations, such as 0.1, 0.5, 1 and 3 wt%, with respect to the PLA matrix. The glass-transition temperature of PLA-based efibers was modulated by adding a 20 wt% of oligomer lactic acid as plasticizer. Once the plasticized PLA-based efibers were obtained and basically characterized in term of morphology as well as thermal and mechanical properties, thermo-mechanical cycles were carried out at 60 °C and 45 °C in order to study their thermally-activated shape memory response, demonstrating that their crystalline nature strongly affects their shape memory behavior. Importantly, we found that the plastificant effect in the mechanical response of the reinforced plasticized PLA efibers is balanced with the reinforcing effect of the MgO NPs, obtaining the same mechanical response of neat PLA fibers. Finally, both the strain recovery and strain fixity ratios of each of the plasticized PLA-based efibers were calculated, obtaining excellent thermally-activated shape memory response at 45 °C, demonstrating that 1 wt% MgO nanoparticles was the best concentration for the plasticized system.

Design of multi-material sound transmission blocker using additive manufacturing

Additive manufacturing is most commonly done through 3D printing, which can print in multiple materials. This enables the design and construction of new structures that can block sound transmission, such as a periodic array of TPU plastic cylinders embedded in a matrix of PLA plastic. The difference in wave speed between the plastics can cause reflections and interference inside the material. However, printing in multimaterials provides distinct challenges for the current 3D printing technology. When printing with multiple nozzles, the inactive nozzle can clog, and getting the two materials to fuse can yield warping and separation. We addressed these problems to fabricate a sample of TPU cylinders (1.8 cm diameter, 8.6 cm height) embedded in PLA (20 cm × 10 cm × 2 cm) and measured the change in STL relative to a block of PLA. We discovered an improved attenuation of about 5.5 dB at 6300 Hz.

FDM 3D PRINTING PROCESS PARAMETERS OPTIMIZATION USING TAGUCHI METHOD FOR IMPROVING THE GEAR STRENGTH

In the recent years, 3D printing has become a topic of great interest from both academic and the industrial sector through the increasing importance of Industry 4.0. This technology is based on layer-by-layer melting of materials to create a three-dimensional object. It is also known as additive production, and it is feasible through several different methods such as stereolithography, selective laser melting and sintering (SLM, SLS), these are just some of the examples, but fused decomposition modeling (FDM) has become the most interesting technique.This paper seeks to analyze the fracture strength (torque) of coupled gears made out of PLA plastic produced by the 3D printing process. To reduce the number of experimental measurements, the Taguchi L8(27) orthogonal array was used to analyze the influence of factors on two level. Investigated factors were: wall thickness, infill and number of infill lines, layer height, temperature, cooling and speed. Finally, optimization of most influential factors according to maximum torque was preformed, using Taguchi method too.