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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]

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]

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]