A route to improving elongation of high-temperature laser sintered PEKK

Benedetti, L.; Brûlé, B; Decraemer, N.; Davies, Richard J.; Evans, K.; Ghita, Oana

doi:10.1016/j.addma.2020.101540

Cited by 8 publications

(19 citation statements)

References 32 publications

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“…The crystallisation behaviour of PEKK (60/40) has been investigated extensively 21,22 . The time–temperature–transformation (TTT) diagram of PEKK (60/40) developed by Choupin et al 21 .…”

Section: Discussionmentioning

confidence: 99%

Mechanical property variance amongst vertical fused filament fabricated specimens via four different printing methods

Davies

Nan

McCutchion

et al. 2021

Polymer International

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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.

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Section: Discussionmentioning

confidence: 99%

Mechanical property variance amongst vertical fused filament fabricated specimens via four different printing methods

Davies

Nan

McCutchion

et al. 2021

Polymer International

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Section: Mechanical Propertiesmentioning

confidence: 97%

“…Figure 4 also summarizes the compressive strength and modulus of the four investigated materials. The semi-crystalline PEEK resulted in the highest strength and modulus, a mechanism associated with the stronger and stiffer effect of the spherulites in the polymeric structure [31,54]. The fracture profile of the lattices following the compression testing is shown in Figure 5, where the ductility features of the amorphous PEEK are observed.…”

Section: Mechanical Propertiesmentioning

confidence: 98%

“…The fracture profile of the lattices following the compression testing is shown in Figure 5, where the ductility features of the amorphous PEEK are observed. Because of lack of crystallinity in the structure, the PEEK lattices reach the densification point without a visible fracture as shown in Figure 5a,c [54]. In contrast, the semi-crystalline PEEK displays a clear failure across the lattice struts as shown in Figure 5b.…”

Section: Mechanical Propertiesmentioning

confidence: 98%

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Thermoplastic Extrusion Additive Manufacturing of High-Performance Carbon Fiber PEEK Lattices

et al. 2021

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Polyetheretherketone (PEEK) has been the focus of substantial additive manufacturing research for two principal reasons: (a) the mechanical performance approaches that of aluminum at relatively high temperatures for thermoplastics and (b) the potential for qualification in both the aerospace and biomedical industries. Although PEEK provides outstanding strength and thermal stability, printing can be difficult due to the high melting point. Recently, high-temperature soluble support has enabled the printing of lattices and stochastic foams with overhanging features in these high-performance carbon fiber thermoplastics, in which density can be optimized to strike a balance between weight and strength to enhance performance in applications such as custom implants or aerospace structures. Although polymer powder bed fusion has long been capable of the combination of these geometries and materials, material extrusion with high-temperature sacrificial support is dramatically less expensive. This research provides a comprehensive mechanical analysis and CT-scan-based dimensional study of carbon fiber PEEK lattice structures enabled with high-temperature support and including model validation.

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“…It is interesting to note that at 280 °C, the PEKK 50/50 crystallization rate remains slow, t 1/2 ∼ 20 min, indicating a slow evolution of the rheological properties of the molten powder at this temperature, a prerequisite for good coalescence and consolidation. 47,54 Figure 10b shows the evolution of the complex viscosity of PEKK 50/50 at 280 °C after melting at 380 °C. The viscosity remains almost constant for a time of ∼10 min, during which the grains can coalesce.…”

Section: Is Pekk 50/50 a Good Candidate For Ht-ls?mentioning

confidence: 99%

Thermal and Crystallization Properties of the Alternated Tere/Iso PEKK Copolymer: Importance in High-Temperature Laser Sintering

Cherri

Iliopoulos

Régnier

et al. 2022

ACS Appl. Polym. Mater.

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High-temperature laser sintering (HT-LS) is a very promising additive manufacturing process for the production of parts of complex geometry for highly demanding applications. Poly(aryl ether ketone) polymers such as poly(ether ketone), poly(ether ether ketone), and poly(ether ketone ketone) (PEKK) have attracted increasing interest during the last decade for use in HT-LS. Among them, PEKK offers the advantage of exhibiting tunable melting temperature and crystallization rate due to its copolymer structure. Indeed, PEKK is synthesized by Friedel−Crafts polyacylation condensation of diphenyl ether with terephthaloyl chloride (T units) and isophthaloyl chloride (I units). In this work, we focus on a specific member of the PEKK family having a regular alternated T/I structure, PEKK 50/50, and study its isothermal crystallization from the melt at various crystallization temperatures (T C ), from 200 °C to 290 °C. A quantitative analysis based on X-ray scattering and differential scanning calorimetry experiments is performed. Primary crystallization dominates the process with a half-time of crystallization higher than 6 min and an Avrami exponent between 2.2 and 3. Stacks of periodic crystalline lamellae are first created, followed by lateral growth of these crystalline lamellae, leading to a gradual increase of the weight crystallinity. Crystalline form I, with traces of form III, is mostly observed regardless of T C . The amount and perfection of the crystalline phase increase with T C . The crystalline state achieved, as well as the thermal and rheological behavior of PEKK 50/50 during crystallization at high T C (∼280−290 °C), are promising for use in HT-LS manufacturing.

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A route to improving elongation of high-temperature laser sintered PEKK

Cited by 8 publications

References 32 publications

Mechanical property variance amongst vertical fused filament fabricated specimens via four different printing methods

Mechanical property variance amongst vertical fused filament fabricated specimens via four different printing methods

Thermoplastic Extrusion Additive Manufacturing of High-Performance Carbon Fiber PEEK Lattices

Thermal and Crystallization Properties of the Alternated Tere/Iso PEKK Copolymer: Importance in High-Temperature Laser Sintering

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