Re-use of polyamide-12 in powder bed fusion and its effect on process-relevant powder characteristics and final part properties

Sanders, Benjamin; Cant, Edward; Jenkins, Michael

doi:10.1016/j.addma.2024.103961

Cited by 4 publications

(3 citation statements)

References 53 publications

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“…This could contribute to the anisotropic behaviour often observed in LS parts, whereby vertically orientated samples have the weakest tensile strength and are the most brittle [ 53 , 56 ]. Overall, un-molten particles and reduced melt flow rate cause reduced material coalescence, resulting in surface defects (orange peel) [ 34 ] and increased porosity [ 32 , 35 , 57 ] within parts fabricated from re-used powder. Increased porosity reduces part strength and induces embrittlement [ 32 , 36 ], which could render LS parts un-fit for purpose, particularly in critical end-use applications.…”

Section: Resultsmentioning

confidence: 99%

“…However, these changes are followed by a plateau, whereby the difference across the next four build cycles is minimal. It has been suggested previously that polycondensation occurs more rapidly in thermally unstressed material, i.e., virgin PA-12 powder; in used, aged powder, further chain growth is hindered by a reduced availability of end groups [ 6 , 12 , 30 , 57 ].…”

Section: Resultsmentioning

confidence: 99%

“…For example, at an isothermal T c of 162 • C, there is a 3.45% reduction in absolute crystallinity between virgin powder and material recovered from build 2; similarly, T m increases by 0.9 • C. However, these changes are followed by a plateau, whereby the difference across the next four build cycles is minimal. It has been suggested previously that polycondensation occurs more rapidly in thermally unstressed material, i.e., virgin PA-12 powder; in used, aged powder, further chain growth is hindered by a reduced availability of end groups [6,12,30,57].…”

Section: The Effect Of Powder Re-use On Crystallisation Behaviour Of ...mentioning

confidence: 99%

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The Effect of Powder Re-Use on the Coalescence Behaviour and Isothermal Crystallisation Kinetics of Polyamide 12 within Powder Bed Fusion

Sanders,

Cant,

Kelly

et al. 2024

Polymers

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Polymer powder bed fusion (PBF) is becoming increasingly popular for the fabrication of lightweight, high-performance parts, particularly for medical and aerospace applications. This study investigates the effect of powder re-use and material aging on the coalescence behaviour, melt flowability, and isothermal crystallisation kinetics of polyamide-12 (PA-12) powder. With increased powder re-use, a progressive reduction in melt flowability and material coalescence is observed; at 200 °C, the particle consolidation time increases from 15 s in virgin powder to 180 s in powder recovered from build 6. The observed changes in the behaviour of PA-12 were attributed to polycondensation and cross-linking; these aging phenomena also create structural defects, which hinder the rate and extent of primary crystallisation. At an isothermal crystallisation temperature of 165 °C, the crystallisation half-time increased from 12.78 min in virgin powder to 23.95 min in powder re-used across six build cycles. As a result, the commonly used Avrami model was found to be unsuitable for modelling the crystallisation behaviour of aged PA-12 powder, with the co-efficient of determination (R2) reducing from >0.995 for virgin powder to as low as 0.795 for re-used powder. On the other hand, an alternative method, the Hay model, is able to successfully track full phase transformation within re-used powder (R2 > 0.99). These results highlight the importance of selecting the most appropriate model for analysing the crystallisation kinetics of PA-12 powder re-used across multiple build cycles. This understanding is crucial for obtaining the strong mechanical properties and dimensional precision required for the fabrication of functional, end-use parts within PBF.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: The Effect Of Powder Re-use On Crystallisation Behaviour Of ...mentioning

confidence: 99%

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The Effect of Powder Re-Use on the Coalescence Behaviour and Isothermal Crystallisation Kinetics of Polyamide 12 within Powder Bed Fusion

Sanders,

Cant,

Kelly

et al. 2024

Polymers

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Additive manufacturing of a polyamide 12 and silica nanocomposite: A route for the reusability of a thermoplastic selective laser sintering powder

Kaba,

Shah,

Dudaško

et al. 2024

Polymer Composites

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A route for the synthesis and additive manufacturing of a polymer‐silica nanocomposite with polyamide 12 (PA12) polymer as the matrix material and silica nanoparticles as the reinforcing filler, has been presented in this work to enable the reusability of PA12 powder waste. PA12 powder formerly has been used in selective laser sintering to manufacture customized implants and lightweight structural components in the medical, automotive, and aerospace industries. Nano‐sized silica particles with varying dispersibility have been used as a filler with different weight contents (1% and 3%) in PA12 composites. These nanoparticles were coated with polyvinyl alcohol to achieve uniform dispersion. The nanocomposite filaments have been extruded and the final manufactured part has been printed by fused filament fabrication. SEM, EDX, and PSD showed that nanoparticles were homogeneously distributed, and the fabricated structures were crack‐free for adapted processing parameters. DSC, FTIR, and mechanical testing at different processing stages of the material showed enhanced mechanical and thermal properties compared to waste PA12. All manufactured composite structures showed an increase in tensile modulus and tensile strengths up to 30%. This approach can be used to improve the properties of PA12 waste and its further utilization for various applications.Highlights Organic solvent—free method for the reinforcement of waste polyamide 12 material. Comprehensive insight into the dispersity of nano‐silica in polymer matrix. Increase of up to 30% tensile strength for 3 wt% nano‐silica loading.

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Predictive Modeling of Mechanical Properties from Degraded Polyamide 12 Powder in Laser Powder Bed Fusion

Vendittoli,

Mascolo,

Polini

et al. 2024

J. of Materi Eng and Perform

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Re-use of polyamide-12 in powder bed fusion and its effect on process-relevant powder characteristics and final part properties

Cited by 4 publications

References 53 publications

The Effect of Powder Re-Use on the Coalescence Behaviour and Isothermal Crystallisation Kinetics of Polyamide 12 within Powder Bed Fusion

The Effect of Powder Re-Use on the Coalescence Behaviour and Isothermal Crystallisation Kinetics of Polyamide 12 within Powder Bed Fusion

Additive manufacturing of a polyamide 12 and silica nanocomposite: A route for the reusability of a thermoplastic selective laser sintering powder

Predictive Modeling of Mechanical Properties from Degraded Polyamide 12 Powder in Laser Powder Bed Fusion

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