Selection Route of Precursor Materials in 3D Printing Composite Filament Development for Biomedical Applications

Additive manufacturing or 3D printing technologies might advance the fabrication sector of personalised biomaterials with high-tech precision. The selection of optimal precursor materials is considered the first key-step for the development of new printable filaments destined for the fabrication of products with diverse orthopaedic/dental applications. The selection route of precursor materials proposed in this study targeted two categories of materials: prime materials, for the polymeric matrix (acrylonitrile butadiene styrene (ABS), polylactic acid (PLA)); and reinforcement materials (natural hydroxyapatite (HA) and graphene nanoplatelets (GNP) of different dimensions). HA was isolated from bovine bones (HA particles size < 40 μm, <100 μm, and >125 μm) through a reproducible synthesis technology. The structural (FTIR-ATR, Raman spectroscopy), morphological (SEM), and, most importantly, in vitro (indirect and direct contact studies) features of all precursor materials were comparatively evaluated. The polymeric materials were also prepared in the form of thin plates, for an advanced cell viability assessment (direct contact studies). The overall results confirmed once again the reproducibility of the HA synthesis method. Moreover, the biological cytotoxicity assays established the safe selection of PLA as a future polymeric matrix, with GNP of grade M as a reinforcement and HA as a bioceramic. Therefore, the obtained results pinpointed these materials as optimal for future composite filament synthesis and the 3D printing of implantable structures.

The Natural Moisture of ABS Filament and Its Influence on the Quality of FFF Products

The article presents the results of research on the influence of the natural moisture of a filament made of acrylonitrile-butadiene-styrene terpolymer (ABS) on the mechanical properties and quality of products fabricated with fused filament fabrication (FFF). The concept of the natural moisture of the filament was defined, and the range of its variability was identified in reference to the range of the natural ambient humidity. It is shown that a change in the ambient humidity by 10% resulted in a change in filament moisture by about 0.05%. The results of the research on the moisture variability of an ABS filament stored in a package, an airtight container, or a container with a moisture absorber are also discussed. The last part of the article presents the results of the research on the impact of the moisture of the filament in its natural range of variability on select mechanical properties of filaments and products made using FFT. It is shown that this impact was significant and had a value of 1 MPa on 0.1% filament moisture.

Influence of Cr Ion Bombardment on the Growth of Cu Coatings Deposited by Magnetron Sputtering on ABS Substrates

Cu coatings were deposited on acrylonitrile-butadiene-styrene copolymer (ABS) substrates by DC magnetron sputtering with Cu target. Cr ions generated by arc evaporation were used to bombard the ABS substrates before the Cu coating process. The influences of the Cr ion bombardment on the surface topography and chemical bonds of the ABS substrates and the adhesion of the Cu coatings on the ABS substrate were studied using scanning electron microscopy, Fourier transform infrared spectroscopy, and micro-Scratch Tester as a function of bias voltage and treatment duration. The results show that the Cr ion bombardment causes Cr particles to embed in the surface. The Cr particles can interlock with the Cu coatings and ABS substrate and significantly improve the coating adhesion. In addition, the Cr particles can act as the nucleation sites of the Cu coatings and facilitate the growth of columnar crystals. Increasing the duration of Cr ion bombardment increases the number of Cr particles and, thus, enhances the adhesion. However, the continuous bombardment results in the degeneration of the ABS surface, causing the formation of the coarse columnar structure of the Cu coatings. Increasing the bias voltage can increase the energy of the Cr particles without causing degeneration of the ABS. The Cu coating deposited on the ABS substrate treated by Cr ion with high-bias voltage and short duration shows a dense and smooth growth structure. In contrast, the bombardment of the Cr ions carried out at high-bias voltage induces the formation of an interfacial layer (amorphous carbon-rich phase) in the ABS surface, which decreases the coating adhesion. It is believed that Cu coatings with strong adhesion and dense structures could be acquired on ABS substrates by optimizing the bias voltage and duration of the Cr ion bombardment pre-treatment.

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.

Compressive and Flexural Strengths of Mortars Containing ABS and WEEE Based Plastic Aggregates

The incorporation of plastic aggregates as a partial replacement of natural aggregates in cementitious materials is interesting in several ways. From a mechanical point of view, the partial substitution of sand with plastic aggregates could improve some properties (e.g., ductility, thermal insulation). This paper deals with the mechanical strength of mortars containing plastic aggregates as a partial replacement of sand. Part of the volume of sand in cement mortars is substituted with plastic aggregates which originate from WEEE (Waste from Electrical and Electronic Equipment) and consist of a mix of ABS (acrylonitrile-butadiene styrene), HIPS (high impact polystyrene) and PP (Polypropylene), or of monomaterial ABS from WEEE sorting. Three rates of replacement (by volume of sand) were tested: 10%, 15% and 30%. Mechanical tests were performed according to European standard EN196-1. The results show that compressive and flexural strength decrease with rate of replacement, but remain satisfactory for structural purposes. In addition, the density of mortar is reduced with the incorporation of plastic aggregates. The decrease of mechanical strength is mainly due to the weak bond between cement paste and plastic aggregates leading to the increase of porosity. Furthermore, it appears that mortars containing plastic aggregates could present a ductile rupture.

Amniotic band sequence in vascular Ehlers-Danlos Syndrome (EDS): Experience of the EDS National Diagnostic Services in the UK

The association between vascular Ehlers-Danlos Syndrome (vEDS) and amniotic band sequence (ABS) has been previously reported in the literature, mostly in single patient case reports. Here, we aim to extend the current knowledge of this association through a case series of five unrelated individuals with ABS in association with molecularly confirmed vEDS, in addition to undertaking a comprehensive literature review. All the individuals were recruited through the EDS national diagnostic service in the UK following appropriate history, physical examination and genetic investigations. Clinical presentation ranged from a single constriction ring to complex craniofacial clefts to limb reduction deformities, reflecting the spectrum of ABS presentation. vEDS was inherited paternally (n = 2), maternally (n = 2) and de novo (n = 1). Previously, maternal vEDS was considered the risk factor for ABS, but our findings suggest that it may be the disease status of the fetus which poses the main risk. It is established that amniotic membrane is derived from fetal tissue, which supports our conclusions. Our observations suggest the increased risk of ABS in fetuses with vEDS. Therefore, exploring family history and features that may suggest vEDS diagnosis in patients with ABS might be useful. We also recommend that a collaborative international study would be useful to help gain a better insight into this association.

Wear and Service Life of 3-D Printed Polymeric Gears

Plastic gears are mostly used in the textile, food, and automotive industries due to their silent operation, corrosion resistance, and light and cheap advantages. Plastic gears are generally manufactured by injection molding or hobbing methods. The excess costs of the molds used to produce parts in injection molding and the problems of wastes that occur during production in hobbing lead companies to additive manufacturing, which is an alternative application. In the additive manufacturing method, the desired amount of product is produced without the problem of waste. In this study, the wear resistance of plastic spur gears produced by the Fused Deposition Modeling (FDM) method was determined theoretically. In order to determine the service life of gears, wear tests were carried out in the Forschungsstelle fur Zahnrader und Getriebebau (FZG) type test device at the same load and rotational speeds. polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyethylene terephthalate (PETG) thermoplastic polymer materials were used in the production of gears. When the gears rotate at the same load and rotational speeds, the most wear was observed in ABS, PLA, and PETG at the theoretically calculated wear depths. PETG is the most resistant material in terms of wear.

Material Extrusion of Structural Polymer-Aluminum Joints-Examining Shear Strength, Wetting, Polymer Melt Rheology and Aging

Generating polymer–metal structures by means of additive manufacturing offers huge potential for customized, sustainable and lightweight solutions. However, challenges exist, primarily with regard to reliability and reproducibility of the additively generated joints. In this study, the polymers ABS, PETG and PLA, which are common in material extrusion, were joined to grit-blasted aluminum substrates. Temperature dependence of polymer melt rheology, wetting and tensile single-lap-shear strength were examined in order to obtain appropriate thermal processing conditions. Joints with high adhesive strength in the fresh state were aged for up to 100 days in two different moderate environments. For the given conditions, PETG was most suitable for generating structural joints. Contrary to PETG, ABS–aluminum joints in the fresh state as well as PLA–aluminum joints in the aged state did not meet the demands of a structural joint. For the considered polymers and processing conditions, this study implies that the suitability of a polymer and a thermal processing condition to form a polymer–aluminum joint by material extrusion can be evaluated based on the polymer’s rheological properties. Moreover, wetting experiments improved estimation of the resulting tensile single-lap-shear strength.

Fracture Load Predictions in Additively Manufactured ABS U-Notched Specimens Using Average Strain Energy Density Criteria

This paper provides a methodology for the prediction of fracture loads in additively manufactured ABS material containing U-notches. The approach is based on the Average Strain Energy Density (ASED) criterion, which assumes that the material being analysed develops fully linear-elastic behaviour. Thus, in those cases where the material has a certain (non-negligible) amount of non-linear behaviour, the ASED criterion needs to be corrected. In this sense, in this paper, the ASED criterion is also combined with the Equivalent Material Concept (EMC) and the Fictitious Material Concept (FMC), both being corrections in which the non-linear real material is substituted by a linear equivalent or fictitious material, respectively. The resulting methodologies have been applied to additively manufactured ABS U-notched single-edge-notched bending (SENB) specimens combining five different notch radii (0, 0.25, 0.5, 1 and 2 mm) and three different raster orientations (0/90, 45/−45 and 30/−60). The results obtained demonstrate that both the ASED-EMC and the ASED-FMC combined criteria provide more accurate predictions than those obtained directly through the ASED criterion, with the ASED-EMC criterion generally providing safe more accurate predictions, with an average deviation from the experimental fracture loads between +1.0% (predicted loads higher than experimental loads) and −7.6% (predicted loads lower than experimental loads).

Interdependencies between Dynamic Response and Crack Growth in a 3D-Printed Acrylonitrile Butadiene Styrene (ABS) Cantilever Beam under Thermo-Mechanical Loads

Acrylonitrile butadiene styrene (ABS) is the most commonly used thermoplastic printing material for fused deposition modelling (FDM). FDM ABS can be used in a variety of complex working environments. Notably, the thermo-mechanical coupled loads under complex operating conditions may lead to cracking and ultimately catastrophic structural failure. Therefore, it is crucial to determine the crack depth and location before a structural fracture occurs. As these parameters affect the dynamic response of the structure, in this study, the fundamental frequency and displacement amplitude response of a cracked 3D-printed ABS cantilever beam in a thermal environment were analytically and experimentally investigated. The existing analytical model, specifically the torsional spring model used to calculate the fundamental frequency change to determine the crack depth and location was enhanced by the proposed Khan-He model. The analytical relationship between the displacement amplitude and crack was established in Khan-He model and validated for the first time for FDM ABS. The results show that a reduced crack depth and location farther from the fixed end correspond to a higher fundamental frequency and displacement amplitude. An elevated ambient temperature decreases the global elastic modulus of the cracked beam and results in a lower fundamental frequency. Moreover, a non-monotonic relationship exists between the displacement amplitude and ambient temperature. The displacement amplitude is more sensitive to the crack change than the fundamental frequency in the initial stages of crack growth.

ABS/Silicon Dioxide Micro Particulate Composite from 3D Printing Polymeric Waste

In this paper, Acrylonitrile-Butadiene-Styrene matrix composites reinforced with Nano-silica dioxide particles were examined and prepared to study their mechanical properties. The composite sheets were pre-prepared using the hot extrusion process. Due to its wide characteristics, silica dioxide additions can strengthen the usability and mechanical features of composite thermoplastics and polymers. Furthermore, introducing silica dioxide as a filler in various attributes can help to maintain the smooth flow of sufficient powders, reduce caking, and manage viscoelasticity. Despite its advantages, 3D printing generates a significant amount of waste due to limited prints or destroyed support structures. ABS is an ideal material to use because it is a thermoplastic and amorphous polymer with outstanding thermal properties that is also applicable with the FFF (Fused Filament Fabrication) technique. The findings showed that increasing the silica dioxide content reduces the tensile strength to 22.4 MPa at 10 wt%. Toughness, ductility, and yield stress values of ABS/silica dioxide composites at 15 wt% increased, indicating that the composite material reinforced by the silica dioxide particles improved material characteristics. It is essential to consider the impact of recycling in polymer reinforcement with fillers. Furthermore, the improved mechanical qualities of the composite material encourages successful ABS recycling from 3D printing, as well as the possibility of reusing it in a similar application.

The Effect of Disinfectants Absorption and Medical Decontamination on the Mechanical Performance of 3D-Printed ABS Parts

Producing parts by 3D printing based on the material extrusion process determines the formation of air gaps within layers even at full infill density, while external pores can appear between adjacent layers making prints permeable. For the 3D-printed medical devices, this open porosity leads to the infiltration of disinfectant solutions and body fluids, which might pose safety issues. In this context, this research purpose is threefold. It investigates which 3D printing parameter settings are able to block or reduce permeation, and it experimentally analyzes if the disinfectants and the medical decontamination procedure degrade the mechanical properties of 3D-printed parts. Then, it studies acetone surface treatment as a solution to avoid disinfectants infiltration. The absorption tests results indicate the necessity of applying post-processing operations for the reusable 3D-printed medical devices as no manufacturing settings can ensure enough protection against fluid intake. However, some parameter settings were proven to enhance the sealing, in this sense the layer thickness being the most important factor. The experimental outcomes also show a decrease in the mechanical performance of 3D-printed ABS (acrylonitrile butadiene styrene) instruments treated by acetone cold vapors and then medical decontaminated (disinfected, cleaned, and sterilized by hydrogen peroxide gas plasma sterilization) in comparison to the control prints. These results should be acknowledged when designing and 3D printing medical instruments.

Biocompatible Customized 3D Bone Scaffolds Treated with CRFP, an Osteogenic Peptide

BACKGROUND

Currently used synthetic bone graft substitutes (BGS) are either too weak to bear the principal load or if metallic, they can support loading, but can lead to stress shielding and are unable to integrate fully. In this study, we developed biocompatible, 3D printed scaffolds derived from µCT images of the bone that can overcome these issues and support the growth of osteoblasts.

METHODS

Cylindrical scaffolds were fabricated with acrylonitrile butadiene styrene (ABS) and Stratasys^® MED 610 (MED610) materials. The 3D-printed scaffolds were seeded with Mus musculus calvaria cells (MC3T3). After the cells attained confluence, osteogenesis was induced with and without the addition of calcitonin receptor fragment peptide (CRFP) and the bone matrix production was analyzed. Mechanical compression testing was carried out to measure compressive strength, stiffness, and elastic modulus.

RESULTS

For the ABS scaffolds, there was a 9.8% increase in compressive strength (p < 0.05) in the scaffolds with no pre-coating and the treatment with CRFP, compared to non-treated scaffolds. Similarly, MED610 scaffolds treated with CRFP showed an 11.9% (polylysine pre-coating) and a 20% (no pre-coating) increase (p < 0.01) in compressive strength compared to non-treated scaffolds.

CONCLUSIONS

MED610 scaffolds are excellent BGS as they support osteoblast growth and show enhanced bone growth with enhanced compressive strength when augmented with CRFP.

Thermal Deformations of Thermoplast during 3D Printing: Warping in the Case of ABS

This research focuses on thermal deformations of thermoplast during three-dimensional printing. A filament acrylonitrile butadiene styrene was used, and the main focus was put on warping. Twenty-seven cuboids divided in six categories by their length, height, surface area, color, nozzle temperature and bed temperature were printed by Fused Filament Fabrication 3D printer. The whole process was captured by a thermal camera and the movies were used to analyze the temperature distribution during printing. All printouts were measured and scanned with a 3D scanner in order to highlight any abbreviations from the original digital models. The obtained results were used to formulate some general conclusions on the influence of selected parameters on the warping process. Based on the outcomes of the study, a set of guidelines on how to minimalize warping was proposed.

Modelling and Investigation of Crack Growth for 3D-Printed Acrylonitrile Butadiene Styrene (ABS) with Various Printing Parameters and Ambient Temperatures

Three-dimensional (3D) printing is one of the significant industrial manufacturing methods in the modern era. Many materials are used for 3D printing; however, as the most used material in fused deposition modelling (FDM) technology, acrylonitrile butadiene styrene (ABS) offers good mechanical properties. It is perfect for making structures for industrial applications in complex environments. Three-dimensional printing parameters, including building orientation, layers thickness, and nozzle size, critically affect the crack growth in FDM structures under complex loads. Therefore, this paper used the dynamic bending vibration test to investigate their influence on fatigue crack growth (FCG) rate under dynamic loads and the Paris power law constant C and m. The paper proposed an analytical solution to determine the stress intensity factor (SIF) at the crack tip based on the measurement of structural dynamic response. The experimental results show that the lower ambient temperature, as well as increased nozzle size and layer thickness, provide a lower FCG rate. The printing orientation, which is the same as loading, also slows the crack growth. The linear regression between these parameters and Paris Law's coefficient also proves the same conclusion.

Rheological and Morphological Properties of Oil Palm Fiber-Reinforced Thermoplastic Composites for Fused Deposition Modeling (FDM)

Fused deposition modelling (FDM) is a filament-based rapid prototyping technology that allows new composite materials to be introduced into the FDM process as long as they can be manufactured in feedstock filament form. The purpose of this research was to analyze the rheological behavior of oil palm fiber-reinforced acrylonitrile butadiene styrene (ABS) composites when used as a feedstock material, as well as to determine the best processing conditions for FDM. The composite’s shear thinning behavior was observed, and scanning electron microscopy was used to reveal its composition. The morphological result found that there was a good fiber/matrix adhesion with a 3 wt% fiber loading, as no fiber pullouts or gaps developed between the oil palm fiber and ABS. However, some pores and fiber pullouts were found with a 5 and 7 wt% fiber loading. Next, the rheological results showed that the increment of fiber content (wt%) increased the viscosity. This discovery can definitely be used in the extrusion process for making wire filament for FDM. The shear thinning effect was increased by adding 3, 5, or 7 wt% of oil palm fiber. The non-Newtonian index (n) of the composites increased as the number of shear rates increased, indicating that the fiber loading had a significant impact on the rheological behavior. As the fiber loading increased, the viscosity and shear stress values increased as well. As a result, oil fiber reinforced polymer composites can be used as a feedstock filament for FDM.

Validation of 3D printing materials for high dose-rate brachytherapy using ionisation chamber and custom phantom

Methods.Measurements were taken with the Exradin A20 (Standard Imaging) ionisation chamber, and the 'homemade' MARM phantom was made with the 3D Ultimaker 2+ printer using PLA material. The material used for validation was ABS Medical from Smart Materials 3D. The irradiation was undertaken with a¹⁹²Ir source by means of Varian's GammaMed Plus iX HDR equipment. EBT3 films were used to run additional tests. We compared different measurements for PLA, ABS Medical, and water. Additional validation methods, described in the bibliography, were also compared.Results.The measurements with the ionisation chamber that we obtained using the MARM phantom with PLA and ABS within the clinically relevant range (0.5-1.5 cm) differ with respect to the measures in the water reference, by 2.3% and 0.94%, respectively.Discussion.The literature describes highly heterogeneous validation methods, complicating the performance of systematic reviews and comparisons between materials. Thus, creating a phantom represents a single effort that will quickly pay off. This system enables comparisons, ensuring that geometric conditions remain stable-something that is not always possible with radiochromic films. The use of a calibrated ionisation chamber in the corresponding energy range, combined with the 'homemade' MARM phantom applied according to the proposed methodology, allows a differentiation between the attenuation of the material itself and the drop in the dose due to distance.Conclusion.The validation method for 3D printing materials, using an ionisation chamber and the MARM PLA phantom, represents an accessible, standardisable solution for manufacturing brachytherapy applicators.

M SA, Patil AY, Yunus Khan TM, Makannavar R. Influence of Solid Lubricant Addition on Friction and Wear Response of 3D Printed Polymer Composites

In this study, acrylonitrile butadiene styrene (ABS) and graphite powder—a solid lubricant—were filled and characterized for friction and wear responses. The fused deposition modeling (FDM) technique was utilized to synthesize ABS–graphite composites. A twin-screw extrusion approach was employed to create the composite filament of graphite–ABS that is suitable for the FDM process. Three graphite particle ratios ranging from 0% to 5% were explored in the ABS matrix. The wear and friction properties of ABS composites were examined using a pin on disc tribometer at varied sliding velocities and weights. As a result of the graphite addition in the ABS matrix, weight losses for FDM components as well as a decreased coefficient of friction were demonstrated. Furthermore, as the graphite weight percentage in the ABS matrix grows the value of friction and wear loss decreases. The wear mechanisms in graphite filled ABS composites and ABS were extensively examined using scanning electron microscopy and confocal microscopy.

Effects of Printing Parameters on the Fatigue Behaviour of 3D-Printed ABS under Dynamic Thermo-Mechanical Loads

Fused deposition modelling (FDM) is the most widely used additive manufacturing process in customised and low-volume production industries due to its safe, fast, effective operation, freedom of customisation, and cost-effectiveness. Many different thermoplastic polymer materials are used in FDM. Acrylonitrile butadiene styrene (ABS) is one of the most commonly used plastics owing to its low cost, high strength and temperature resistance. The fabricated FDM ABS parts commonly work under thermo-mechanical loads in actual practice. For producing FDM ABS components that show high fatigue performance, the 3D printing parameters must be effectively optimized. Hence, this study evaluated the bending fatigue performance for FDM ABS beams under different thermo-mechanical loading conditions with varying printing parameters, including building orientations, nozzle size, and layer thickness. The combination of three building orientations (0°, ±45°, and 90°), three nozzle sizes (0.4, 0.6, and 0.8 mm) and three-layer thicknesses (0.05, 0.1, and 0.15 mm) were tested at different environmental temperatures ranging from 50 to 70 °C. The study attempted to find the optimal combination of the printing parameters to achieve the best fatigue behaviour of the FDM ABS specimen. The experiential results showed that the specimen with 0° building orientation, 0.8 mm filament width, and 0.15 mm layer thickness vibrated for the longest time before the fracture at each temperature. Both a larger nozzle size and thicker layer height can increase the fatigue life. It was concluded that printing defects significantly decreased the fatigue life of the 3D-printed ABS beam.

Brominated flame retardants extraction from waste electrical and electronic equipment-derived ABS using supercritical carbon dioxide

Persistent organic pollutants such as brominated flame retardants represent a major problem in the end-of-life of polymer materials. This study investigates the extraction of brominated flame retardants (BFR) from real waste electrical and electronic equipment (WEEE) using supercritical carbon dioxide (sc-CO₂). Sc-CO₂ is a non-toxic solvent which possesses intermediate properties between liquids and gases which confer it high diffusivity and solubility. A batch of WEEE-derived acrylonitrile-butadienestyrene (ABS) was first characterized to determine its bromine and BFR composition which was found to be four times higher than the regulation limit set in 2019. Then, different parameters of the sc-CO₂ process such as temperature, pressure, granulometry and the use of a co-solvent were studied to estimate the effect of each one on the BFR extraction efficiency. With the view to determine the recyclability of the treated polymer, the impact of the extraction process on the polymer material was also studied by Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Size Exclusion Chromatography (SEC). The extraction process performed on <500 µm particle size sample at 40 °C and 500 bars during 6 h and using ethanol as a co-solvent allowed to remove 43.5 ± 0.9% of bromine, which was the maximum extraction rate obtained. Sc-CO₂ extraction was found to be an efficient technique to remove tetrabromobisphenol A (TBBPA) but the tested conditions did not allow to remove enough polybromodiphenylethers (PBDE) to satisfy the regulation. Sc-CO₂ process seems to be a promising pre-treatment method prior to mechanical recycling as no degradation effect on the polymer matrix was observed.

Investigations on Melt Flow Rate and Tensile Behaviour of Single, Double and Triple-Sized Copper Reinforced Thermoplastic Composites

Thermoplastic composite materials are emerging rapidly due to the flexibility of attaining customized mechanical and melt flow properties. Due to high ductility, toughness, recyclability, and thermal and electrical conductivity, there is ample scope of using copper particles in thermoplastics for 3d printing applications. In the present study, an attempt was made to investigate the Melt Flow Index (MFI), tensile strength, and electrical and thermal conductivity of nylon 6 and ABS (acrylonitrile butadiene styrene) thermoplastics reinforced with copper particles. Thus, the experiments were conducted by adding different-sized copper particles (100 mesh, 200 mesh, and 400 mesh) in variable compositions (0% to 10%) to ABS and nylon 6 matrix. The impact of single, double, and triple particle-sized copper particles on MFI was experimentally investigated followed by FTIR and SEM analysis. Also, the tensile, electrical, and thermal conductivity testing were done on filament made by different compositions. In general, higher fluidity and mechanical strength were obtained while using smaller particles even with higher concentrations (up to 8%) due to improved bonding strength and adhesion between the molecular chains. Moreover, thermal and electrical conductivity was improved with an increase in concentration of copper particles.

An Analysis of Polymer Gear Wear in a Spur Gear Train Made Using FDM and FFF Methods Based on Tooth Surface Topography Assessment

This article focuses on wear tests of spur gears made with the use of additive manufacturing techniques from thermoplastic materials. The following additive manufacturing techniques were employed in this study: Melted and Extruded Modelling (FDM) and Fused Filament Fabrication (FFF). The study analysed gears made from ABS M-30 (Acrylonitrile Butadiene Styrene), ULTEM 9085 (PEI Polyetherimide) and PEEK (Polyetheretherketone), and the selection of these materials reflects their hierarchy in terms of economical application and strength parameters. A test rig designed by the authors was used to determine the fatigue life of polymer gears. Gear trains were tested under load in order to measure wear in polymer gears manufactured using FDM and FFF techniques. In order to understand the mechanism behind gear wear, further tests were performed on a P40 coordinate measuring machine (CMM) and a TalyScan 150 scanning instrument. The results of the gear tests made under load allow us to conclude that PEEK is resistant to wear and gear train operating temperature. Its initial topography undergoes slight changes in comparison to ABS M-30 and Ultem 9085. The biggest wear was reported for gears made from Ultem 9085. The hardness of the material decreased due to the loaded gear train’s operating temperature.

Do Microplastics Enter Our Food Chain Via Root Vegetables? A Raman Based Spectroscopic Study on Raphanus sativus

The outburst of plastic pollution in terrestrial ecosystems poses a potential threat to agriculture and food safety. Studies have already provided evidence for the uptake of plastic microparticles by several plant species, accompanied by numerous developmental effects, using fluorescence labelling techniques. Here, we introduce the implementation of confocal Raman spectroscopy, a label-free method, for the effective detection of microplastics (MPs) accumulation in the roots of a common edible root vegetable plant, Raphanus sativus, after treatment with acrylonitrile butadiene styrene (ABS) powder. We also demonstrate the concomitant occurrence of phenotypic defects in the polymer-treated plants. We anticipate that this work can provide new insights not only into the extent of the impact this widespread phenomenon has on crop plants but also on the methodological requirements to address it.

Size-Induced Constraint Effects on Crack Initiation and Propagation Parameters in Ductile Polymers

Fracture mechanics are of high interest for the engineering design and structural integrity assessment of polymeric materials; however, regarding highly ductile polymers, many open questions still remain in terms of fully understanding deformation and fracture behaviors. For example, the influence of the constraint and specimen size on the fracture behavior of polymeric materials is still not clear. In this study, a polymeric material with an elastic plastic deformation behavior (ABS, acrylonitrile butadiene styrene) is investigated with regard to the influence of constraint and specimen size. Different single-edge notched bending (SENB) specimen sizes with constant geometrical ratios were tested. The material key curve was used to investigate differences in the constraint, where changes for small and large specimen sizes were found. Based on a size-independent crack resistance curve (J-R curve), two apparent initiation parameters (J_0.2 and J_bl) were determined, namely, the initiation parameter J_ini (based on the crack propagation kinetics curve) and the initiation parameter J_I,lim (based on an ESIS TC 4 draft protocol). It was found that J_0.2 and J_bl could be used as crack initiation parameters whereby J_ini and J_I,lim are indicative of the onset of stable crack growth.