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This paper introduces a pioneering approach that combines ex situ synthesis with advanced manufacturing to develop ZIF-67-PA12 Nylon composites with mixed-matrix membranes (MMMs), with the goal of enhancing hydrogen storage systems. One method involves producing MOF-PA12 composite powders through an in situ process, which is then commonly used as a base powder for powder bed fusion (PBF) to fabricate various structures. However, developing the in situ MOF-PA12 matrix presents challenges, including limited spreadability and processability at higher MOF contents, as well as reduced porosity due to pore blockage by polymers, ultimately diminishing hydrogen storage capacity. To overcome these issues, PBF is employed to form PA12 powder into films, followed by the ex situ direct synthesis of ZIF-67 onto these substrates at loadings exceeding those typically used in conventional MMM composites. In this study, ZIF-67 mass loadings ranging from 2 to 30 wt.% were synthesized on both PA12 powder and printed film substrates, with loadings on printed PA12 films extended up to 60 wt.%. ZIF-67-PA12-60(f) demonstrated a hydrogen capacity of 0.56 wt.% and achieved 1.53 wt.% for ZIF-67-PA12-30(p); in comparison, PA12 exhibited a capacity of 0.38 wt.%. This was undertaken to explore a range of ZIF-67 Metal–organic frameworks (MOFs) to assess their impact on the properties of the composite, particularly for hydrogen storage applications. Our results demonstrate that ex situ-synthesized ZIF-67-PA12 composite MMMs, which can be used as a final product for direct application and do not require the use of in situ pre-synthesized powder for the PBF process, not only retain significant hydrogen storage capacities, but also offer advantages in terms of repeatability, cost-efficiency, and ease of production. These findings highlight the potential of this innovative composite material as a practical and efficient solution for hydrogen storage, paving the way for advancements in energy storage technologies. [ABSTRACT FROM AUTHOR]

To explore the morphology of polyetheretherketone (PEEK), this study employed fast scanning calorimetry (FSC) and scanning electron microscopy (SEM). The objective was to observe the PEEK microstructure under various thermal profiles replicating the additive manufacturing material extrusion process. Samples were observed using SEM directly from the FSC chips, allowing high-accuracy evaluation of the microstructure relative to the thermal profiles. This approach allowed for the evaluation of the microstructure with high accuracy concerning the thermal profiles to which the samples were previously exposed. Each sample was coated with a 10 nm layer of gold–palladium (20–80% ratio), and no etching was necessary to observe the micro features of the microstructure. The approach enabled successful observation and quantification of PEEK microstructure, linking substrate temperature and temperature peaks to microstructural outcomes. Notably, temperature peaks during the process enhanced the formation of well-developed, thick lamellae due to increased chain mobility. Additionally, embryos formed post-remelting of the substrate structure were observed. [ABSTRACT FROM AUTHOR]

The current study investigates the melting behavior of polyetheretherketone (PEEK) using both Differential Scanning Calorimetry (DSC) and Fast Scanning Calorimetry (FSC) thermal analysis techniques. The PEEK melting peaks are examined under various conditions, including isothermal and non‐isothermal crystallization conditions, as well as a thermal profile mimicking the material extrusion process (MEX). The results of the analysis reveal changes in the crystalline morphology, as indicated by a shift in intensity between melting peaks crystalized at different isothermal temperatures and cooling rates. Furthermore, the behavior of the deconvoluted melting peaks differs depending on the substrate temperature during the MEX process simulation. The presence of double or multiple melting peaks suggests the presence of different crystalline populations during the manufacturing process. Understanding the formation and changes in these melting peaks can help inform the development of better printing strategies and improve the mechanical performance of printed parts. [ABSTRACT FROM AUTHOR]

Driven by the need to make high temperature thermoplastic polymers more processable and expand the range of applications, this study reports on the properties of a novel PAEK material developed by Victrex (Thornton Cleveleys, UK) which is capable of undergoing crosslinking or crystallisation, two competing processes that can be adapted via specific processing temperature and time conditions. The uniqueness of this PAEK material resides in its manufacturing approach, where the crosslinkers are incorporated during the polymerisation process, and its distinct properties, including a controllable viscosity that can be tuned from low to high to allow its application in complex manufacturing processes, such as thermoplastic carbon fibre manufacturing. [ABSTRACT FROM AUTHOR]

Achieving good dispersion of graphene (GNP), in polyetheretherketone (PEEK), is challenging due to the high melt viscosity, solvent resistance and processing temperature of PEEK. In addition, certain manufacturing processes tend to enhance the anisotropy due to GNP orientation within the structure. This study investigated the fabrication of nanocomposite parts through hot compression moulding (C-MOULD) and powder bed fusion (PBF) processes, using powder with GNPs fused to the surface of polymeric particles, through a process called mechanofusion. The method applies mechanical forces of compression, shear and impact to generate a mechanical bond between materials, in this case, O2 functionalised GNP and a developmental polyaryletherketones (PAEK) grade powder. The novelty of this work is in the combination of processes used for manufacturing (material preparation and actual manufacturing processes), which are scalable and efficient in comparison with existing methods (such as solvent mixing or melt-compounding). The mechanofusion GNP-PAEK composite powders were successfully printed for the first time using the EOS P800 system with notable improvements in electrical and mechanical properties. This study highlights that the mechanofusion process could be used as an efficient process for making multifunctional nanocomposite materials and this can be combined with additive manufacturing (AM) processes to produce complex components. [ABSTRACT FROM AUTHOR]

Self-folding behavior is an exciting property of weft-knit fabrics that can be created using just front and back stitches. This behavior is easy to create, but not easy to anticipate and currently cannot be predicted by the existing computer-aided design software that controls industrial knitting machines. This work identifies the edge deformation behaviors that lead to self-folding in weft knits, and methods to characterize the mechanical forces driving these behaviors with regard to chosen manufacturing parameters. With this data and analysis of the fabric deformations, the self-folding behavior was purposely controlled using calculated scaling factors. Furthermore, theoretical equations were developed to mathematically predict these scaling factors, minimizing the trial and error required to design with self-folding behavior and create textiles with novel engineered properties. By understanding the mechanisms responsible for creating these three-dimensional self-folding textiles, they can then be designed in a programmable manner for use in technical applications. [ABSTRACT FROM AUTHOR]

The heating and extrusion process in fused filament fabrication (FFF) is significantly shorter than the conventional extrusion process where longer heating times and significant pressure are applied. For this reason, it is important to understand whether the crystal history of the feedstock is fully erased through the FFF process and whether the FFF process can be tailored further by engineering the crystallization of the feedstock filaments. In this context, a methodology for evaluating the influence of morphology and mechanical properties on different feedstock and extruded filaments is proposed. Filaments with three different PEEK 450G crystalline structures (standard crystallinity, drawn filament and amorphous filament) were selected and evaluated, before and after free extrusion. The resulting morphology, crystallinity and mechanical properties of the extruded filaments were compared against the feedstock properties. X-ray diffraction (XRD), transmission electron microscopy (TEM), differential and fast scanning calorimetry (DSC/FDSC) and tensile test were the techniques used to evaluate the materials. The results showed clear differences in the properties of the feedstock materials, while the analysis of the extruded filaments points to a homogenization of the resulting material producing mostly similar mechanical properties. However, the use of the drawn filament highlighted a statistically significant improvement in crystallinity and mechanical performance, especially in strain values. This conclusion suggests the innovative possibility of improving the quality of manufactured parts by tailoring the microstructure of the feedstock material used in the FFF process. [ABSTRACT FROM AUTHOR]

Amongst additive manufacturing processes, fused filament fabrication (FFF) is one of the most affordable and cost‐efficient technologies that can produce complex shaped components with an increasing number of printable polymers such as the polyaryletherketone family, polyetherimide and polyphenylene sulfide. Despite the gain in popularity, there is a lack of standardisation in specimen preparation and mechanical testing of FFF samples. This study investigates the effect of different methods of printing vertical tensile specimens on the mechanical properties when the material and the printing parameters are fixed. A slow crystallising polyetherketoneketone grade was selected as the printing material to exclude the effect of crystallisation on the interlayer bonding strength, leaving the temperature‐dependent amorphous molecular diffusion across the layers as the governing mechanism. Vertical tensile specimens made by four printing methods – individually printed, machined and connected (based on ISO 527‐2‐1A and ISO 527‐2‐1BA) – were assessed. Individually printed vertical specimens were found to have the highest mean tensile strength, owing to the high level of diffusion induced by the very short layer time. The strengths of specimens printed via the other three methods are less sensitive to the effect of layer time, due to the lower rate of change during cooling and its relationship with the local temperature at the interlayer surface. This study highlights the importance of the disclosure of FFF printing methods along with any reported mechanical data. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

This paper introduces a novel extrusion process for manufacturing helical auxetic yarn (HAY). A range of semi-coextruded HAYs have been manufactured in a cost-effective, consistent and readily usable form. The semi-coextruded HAYs were compared to the conventional spun yarns in terms of tensile properties and auxetic behavior. The results show the presence of the auxetic effect in newly fabricated semi-coextruded HAYs. Similar to the traditional spun HAYs, the new HAYs are sensitive to parameters such as the initial wrap angle, the core/wrap diameter ratio and component moduli. Importantly, a few new manufacturing parameters have been identified for tailoring the auxetic behavior of the semi-coextruded HAYs. The semi-coextruded HAYs are auxetic when an instantaneous true Poisson’s ratio analysis method is applied. The semi-coextruded HAYs give a larger maximum negative Poisson’s ratio than the conventional HAYs due to the advantages of the pre-formed helical wrap structure. [ABSTRACT FROM AUTHOR]

This paper discusses various methods of fabrication of plain and carbon-reinforced composite powders, as well as a range of powder characterisation test methods suitable for defining powders for laser sintering. Two milling processes (based on disc blades and rotatory cutting knives) were used as methods of fabrication of powders, starting from injection moulding granule grades, for comparison with current powders obtained directly from polymerisation processes. It was found that the milling process affects the particles properties. The rotary milling produced powders with superior properties in comparison with the disc milling method. Tests including particle size distribution, angle of repose, aspect ratio, sphericity and roundness of particles were employed to compare and assess the suitability of powders for laser sintering. The Brunauer-Emmett-Teller test was identified as a useful method to define surface roughness and porosity of the particles. The carbon fibre (Cf) Poly Ether Ketone (PEK) granules milled well and after an additional sieving process created a good quality powder. This is the first attempt to investigate properties of PEK powder with encapsulated Cf and follow their sintering profile through hot-stage microscopy. It is expected that this type of composite powder will create isotropic structures in comparison with the highly anisotropic properties given by the known dry mix composite powders, currently used in laser sintering. [ABSTRACT FROM AUTHOR]

ABSTRACT The increasing use of bio-sourced and biodegradable polymers such as poly(lactic acid) (PLA) in bottle packaging presents an increasing challenge to the polyethylene terephthalate (PET) recycling process. Despite advanced separation technologies to remove PLA from PET recyclate, PLA may still be found in rPET process streams. This study explores the effects of PLA on the mechanical properties and crystallization behavior of blends of PET containing 0.5-20% PLA produced by injection molding. SEM indicates an immiscible blend of the two polymers and TGA confirms the independent behavior of the two polymers under thermal degradation conditions. Temperature-modulated DSC studies indicate that adding PLA to PET increases the rigid amorphous fraction of the PET moiety. Critical amounts of PLA induce stress oscillation behavior during mechanical testing. The mechanical behavior of the samples is explained by antagonistic interaction between increased rigid amorphous fraction and decreased fracture strength arising from an increased population of PLA microparticles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44147. [ABSTRACT FROM AUTHOR]

As the material extrusion technology overlaps with composite manufacturing, some of the papers examined processing of PEEK composite materials. As the field of macromolecular science celebrated its 100th anniversary in 2020, we organised a special issue of Polymer International devoted to the synthesis, processing and applications of polyaryletherketones (PAEKs). A further area of research not particularly highlighted within this review; but very much an active concern; is the development of PAEK-based thermoplastic composites for application in the aerospace and medical sectors. [Extracted from the article]

The mechanism of interface bonding of a selected nitrile rubber compound vulcanized on polyamide 6 was studied using transmission electron microscopy. The two types of interfaces identified were formed through mechanical clamping and enhanced by hydrogen bonding between polyamide 6 and silane coupling agent in nitrile rubber compound. [ABSTRACT FROM AUTHOR]

The Hague Convention -- 25 October 1980, about the international child abduction -- is the international instrument for the situation in which one of the child's parent changes his usual place against the will of the other parent or refuses to return the child into his usual residence from a member state to another. This law regulates the procedures and the legal adequate solution to prevent the international child abduction, having in view to standardize the legislation of the member states. Conclusively, this article analyzing a sentence from a Romanian Court enshrines that the legal instruments of the national system are not capable to realize the purpose of the Convention: the return of the abducted child into his residence country. [ABSTRACT FROM AUTHOR]

This study examines the recycling of polytetrafluoroethylene (PTFE)/glass fiber (GF) printed circuit boards (PCB) laminates through mechanical grinding and the re-manufacture of new composites incorporating PTFE/GF recyclate using sintering processes with and without pressure (SWOP and SWP). The PTFE/GF recyclate was tested for mechanical and dielectric performance. Experimental data were fitted to modified Lichtenecker and Effective-Medium Theory (EMT) theoretical equations to estimate the dielectric constant of PTFE/GF recyclate subsheets for further use in new PTFE/GF laminates. It was found that the experimental values were inside of the Wiener bounds and fitted well the two theories for both manufacturing methods proposed. Overall, the results showed that PTFE/GF recyclate could be used as replacement for virgin PTFE/GF when incorporated in specific concentrations. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011. [ABSTRACT FROM AUTHOR]