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The amount of radiated energy is known to be a crucial parameter in powder-bed additive manufacturing (AM) processes. The role of irradiance in the multijet fusion (MJF) process has not been addressed by any previous research, despite the key role of this process in the AM industry. The aim of this paper is to explore the relationship between irradiance and dimensional accuracy in MJF.

An experimental activity was carried out to map the relationship between irradiance and dimensional accuracy in the MJF transformation of polyamide 12. Two specimens were used to measure the dimensional accuracy on medium and small sizes. The experiment was run using six different levels of irradiance. For each, the crystallinity degree and part density were measured.

Irradiance was found to be directly proportional to part density and inversely proportional to crystallinity degree. Higher irradiance leads to an increase in the measured dimensions of parts. This highlights a predominant role of the crystallisation degree and uncontrolled peripherical sintering, in line with the previous literature on other powder-bed AM processes. The results demonstrate that different trends can be observed according to the range of sizes.

Rapid tooling has numerous advantages when prototyping injection molded components, but the effects of the tooling on the resulting part properties are often overlooked. The purpose of this paper is to consider the effect of tooling on the final part properties and morphology.

Digital polyacrylonitrile-butadiene-styrene (ABS) tooling and aluminum tooling were used to mold test specimens from isotatic polypropylene (iPP). Tensile behavior, impact strength, shrinkage, surface roughness and porosity were evaluated for both sets of samples. Additionally, differential scanning calorimeter (DSC) and wide-angle X-ray scattering (WAXS) were used to assess the crystallinity of the samples.

Characterization of the molded parts showed that slower cooling rates in the Digital ABS inserts promoted the formation of ß-PP, while this crystal structure was not found in the parts molded using aluminum tooling. Additionally, parts molded on the digital ABS inserts exhibited higher mold shrinkage and SEM images identified microscopic shrinkage voids within the material. The change in morphology and the presence of voids significantly affected the tensile behavior with the parts molded in Digital ABS, which broke with little cold drawing and exhibited higher tensile moduli and higher yield strengths.

The results show that the choice of rapid tooling technique plays an important role on determining the properties of the final parts.

Previous studies have not characterized the effect of rapid tooling on the morphology of the molded articles fully or over a variety of processing conditions. This study builds on prior work by using both WAXS and DSC to characterize morphological changes over a wide range of processing conditions and comparing results to mechanical property and shrinkage data.

This paper aims to provide a detailed study on influence of the laser energy density on mechanical, surface and dimensional properties of polyamide 12 (PA12) parts produced by selective laser sintering (SLS), providing the microstructural and crystallization evolution of the samples produced at different energy densities.

Making use of a space filling design of experiments, a wide range of laser sintering parameters is covered. Surface morphology is assessed by means of profile measurements and scanning electron microscopy (SEM) images. Mechanical testing, SEM, X-ray diffraction (XRD), differential scanning calorimeter (DSC) and infrared spectroscopy (FTIR) were used to assess the influence of energy density on structural and mechanical properties.

Results show a high dependency of the properties on the laser energy density and also a compromise existing between laser exposure parameters and desired properties of laser sintered parts. Surface roughness could be associated to overlap degree when using higher scan line spacing values and lower laser speeds improved surface roughness when high scan line spacing is used. Higher mechanical properties were found at higher energy density levels, but excessively high energy density decreased mechanical properties. A transition from brittle to ductile fracture with increasing energy density could be clearly observed by mechanical analysis and SEM. XRD and DSC measurements show a decrease on the crystal fraction with increasing energy densities, which corroborated the plastic behavior observed, and FTIR measurements revealed polymer degradation through chain scission might occur at too high energy densities.

Valuable guidelines are given regarding energy density optimization for SLS of PA12 considering not only quality criteria but also microstructure characteristics. Surface properties are studied based on the concept of degree of overlap between laser scanning lines. For the first time, crystallization behavior of SLS PA12 parts produced at different energy levels was studied by means of XRD measurements. Polymer degradation of SLS PA12 parts was evaluated with FTIR, which is a non-destructive and easy test to be conducted.

Fused deposition modeling (FDM) is a layer by layer technology with the potential to create complex and individual parts from thermoplastic materials such as ABS. The use of Polylactic acid (PLA) and tricalcium phosphate (TCP) as resorbable composite is state of the art in tissue engineering and maxillofacial surgery. The purpose of this paper is to evaluate the processing conditions and the performance of parts (e.g. mechanical properties) manufactured with a FDM machine.

In this paper, the general suitability of PLA for the processing with FDM is evaluated and material specific effects (e.g. crystallization and shrinkage) are shown. Therefore, the characterization of the semi‐crystalline biodegradable material by thermal, mechanical and microscopic analysis is carried out.

Facts, which affect the functional properties of the samples, are analyzed. Among them, the processing temperature and sample size significantly affect the morphology of the final components. Components from PLA/TCP with sufficient mechanical properties for their potential use as scaffolds are obtained.

Thus, the paper shows that by thermal analysis it is possible to identify major influences on processing and part properties.

To convert the post‐production polyethylene terephthalate (PET)‐containing fabrics waste into new value‐added polymeric materials using maleic anhydride grafted linear low‐density polyethylene (LLDPE‐g‐MAH) for improved toughness and to optimise the results of such a modification.

For effective toughening, various blends were made of polyamide 6 (PA) and post‐production PET‐containing fabrics waste (PET) by incorporating different concentrations of maleic anhydride grafted, linear low‐density polyethylene (LLDPE‐g‐MAH). The reactions of LLDPE‐g‐MAH with blend components were studied by Fourier transformation infrared spectroscopy, solubility behaviour of the products in formic acid and rheological measurements. Blends investigated were prepared in a co‐rotating twin‐screw extruder and characterised by differential scanning calorimetry and scanning electron microscopy. The static tensile property and impact strength of the blends were also measured.

The modification of polyamide 6 and post‐production PET‐containing fabrics waste using LLDPE‐g‐MAH showed significant enhancement of impact and interfacial adhesion over the unmodified one. The modification caused a chemical linkage between LLDPE‐g‐MAH and blend components which led not only to forming PA‐co‐LLDPE‐g‐MAH‐co‐PET copolymers, but also to ensuring the intrinsically strong chemical bonds across LLDPE‐g‐MAH phase/PET phase/PA matrix interface, which was the main cause to the improved impact strength and interface adhesion. The optimum results were obtained at 10 per cent of LLDPE‐g‐MAH.

The post‐production PET‐containing fabrics waste used in the present context was defibrated before processing.

The method developed provided a simple and practical solution to recycling and improving the toughness of post‐production PET‐containing fabrics waste.

The method of recycling post‐production PET‐containing fabrics waste was novel and the new polymeric materials obtained could find numerous applications such as hybrid films, fibres and engineering polymers.

This paper aims to investigate the effect of printing temperature on the thermal and the mechanical behaviour of polylactic acid (PLA)-polyhydroxyalkanoate (PHA) blend printed using fused deposition modelling (FDM).

Because of the use of an infra-red camera, thermal cycling during the laying down is quantified. In addition, X-ray micro-tomography is considered to reveal the microstructural arrangement within the three-dimensional printed material. Tensile loading conditions are used to derive Young’s modulus, tensile strength and fracture toughness, and relate these to the printing temperature. Finite element computation based on three-dimensional microstructure information is used to predict the role of defects on the tensile performance.

The results show a remarkable cohesive structure of PLA-PHA, particularly at 240°C. This cohesive structure is explained by the ability to ensure heat accumulation during laying down as evidenced by the nature of thermal cycling. The printing temperature is found to be a key factor for tuning the ductility of the printed PLA-PHA allowing full restoration of tensile strength at high printing temperature.

This study reports new results related to the thermo-mechanical behaviour of PLA-PHA that did not receive much attention in three-dimensional printing despite its potential as a candidate for pharmacological and medical applications. This study concludes by a wide range of possible printing temperatures for PLA-PHA and a remarkable low porosity generated by FDM.

This study aims to characterize the properties of natural cellulose fiber from the pseudo-stems of the curcuma zedoaria plant.

The fiber was extracted using the biological retting process (cold-water retting). The intrinsic fiber properties obtained were used to evaluate the possibility of using fiber for textile applications.

The average length of a curcuma zedoaria fiber was 34.77 cm with a fineness value of 6.72 Tex. A bundle of curcuma zedoaria fibers was comprised of many elementary fibers. Curcuma zedoaria had an irregular cross-section, with the lumen having a varied oval shape. Curcuma zedoaria fibers had tenacity and elongation value of 3.32 gf/denier and 6.95%, respectively. Curcuma zedoaria fibers had a coefficient of friction value of 0.46. Curcuma zedoaria fibers belong to a hygroscopic fiber type with a moisture regain value of 10.29%.

Extraction and Characterization of Curcuma zedoaria Pseudo-stems Fibers for Textile Application.

The increasing accumulation of synthetic plastic waste in oceans and landfills, along with the depletion of non-renewable fossil-based resources, has sparked environmental concerns and prompted the search for environmentally friendly alternatives. Biodegradable plastics derived from lignocellulosic materials are emerging as substitutes for synthetic plastics, offering significant potential to reduce landfill stress and minimise environmental impacts. This study highlights a sustainable and cost-effective solution by utilising agricultural residues and invasive plant materials as carbon substrates for the production of biopolymers, particularly polyhydroxybutyrate (PHB), through microbiological processes. Locally sourced residual materials were preferred to reduce transportation costs and ensure accessibility. The selection of suitable residue streams was based on various criteria, including strength properties, cellulose content, low ash and lignin content, affordability, non-toxicity, biocompatibility, shelf-life, mechanical and physical properties, short maturation period, antibacterial properties and compatibility with global food security. Life cycle assessments confirm that PHB dramatically lowers CO₂ emissions compared to traditional plastics, while the growing use of lignocellulosic biomass in biopolymeric applications offers renewable and readily available resources. Governments worldwide are increasingly inclined to develop comprehensive bioeconomy policies and specialised bioplastics initiatives, driven by customer acceptability and the rising demand for environmentally friendly solutions. The implications of climate change, price volatility in fossil materials, and the imperative to reduce dependence on fossil resources further contribute to the desirability of biopolymers. The study involves fermentation, turbidity measurements, extraction and purification of PHB, and the manufacturing and testing of composite biopolymers using various physical, mechanical and chemical tests.

Examines the eleventh published year of the ITCRR. Runs the whole gamut of textile innovation, research and testing, some of which investigates hitherto untouched aspects. Subjects discussed include cotton fabric processing, asbestos substitutes, textile adjuncts to cardiovascular surgery, wet textile processes, hand evaluation, nanotechnology, thermoplastic composites, robotic ironing, protective clothing (agricultural and industrial), ecological aspects of fibre properties – to name but a few! There would appear to be no limit to the future potential for textile applications.

Polyamide 12 (PA12) processed by the additive manufacturing technique of selective laser sintering (SLS) is acquiring a leading role in cutting-edge technological sectors pertaining to transport and biomedical among others. In many of these applications, design requirements must ensure fatigue structural integrity. One of the characteristic features of these SLS PA12 is the layer-wise structure that may influence the mechanical response. Therefore, this paper aims to assess the fatigue life behavior of PA12, focusing on the effect of the load direction with respect to the load orientation.

With the aim of analyzing the effect of the load direction with respect to the layer wise structure, fatigue tests on plain samples of SLS PA12 were carried out with the load applied parallel and perpendicular to the layer planes. The S-N stress life curves and the fatigue limit at 106 cycles were determined at room temperature and at a stress ratio of 0.1. The fracture surfaces were inspected to evaluate the damage evolution, modeled via the fracture mechanics methodology to obtain the fracture parameters.

The fatigue resistance was better when the load was applied parallel than when was applied perpendicularly to the layered structure. The analysis of the postmortem specimens evidenced three regions. The inspection of the fatigue macro crack growth region revealed that crazing was the mechanism responsible of nucleation and growth of damage till a macroscopic crack was generated, as well as of the consequent crack advancement. The calculated fracture parameters computed from the application of the fracture mechanics approach were similar to those obtained from standardized fracture tests, except when the stress levels were close to the yield strength.

The fatigue knowledge of polymers, and especially of polymers processed via additive manufacturing techniques, is still scarce. Therefore, the value of this investigation is not only to obtain fatigue data that could be used for structural design with SLS PA12 materials but also to advance in the knowledge of damage evolution during the fatigue process.