Intumescent, catalyzed flame retardant systems for polyamide‐based powder bed fusion

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Abstract Flame‐retardant properties of polymer components are essential to a broad variety of applications. However, the processing of flame‐retardant thermoplastics in laser‐based powder bed fusion remains challenging. To overcome prevailing limitations, a new polyphosphate‐based intumescent flame‐retardant system for polyamide 12 (PA12) based powder bed fusion was developed. For this purpose, PA12 was successfully manufactured in selective laser sintering (SLS) with different combinations of a multi‐component flame‐retardant system, consisting of ammonium polyphosphate (APP), pentaerythritol (PER) and manganese(II) oxide as a catalyst with four different energy densities in the range of 0.25–0.40 J mm − 3 . Relying on thermal and microscopic investigations, the process window was observed to remain unaffected by the intumescent flame‐retardant system. All samples show a similar thermal degradation behavior, independent of the energy density during the manufacturing process, implying no chemical nor physical alterations of the flame‐retardant additives induced by higher energy densities. The flame behavior was analyzed using limiting oxygen index (LOI), UL‐94, and cone calorimeter measurements in combination with thermographic imaging. Maximum LOI values of 32.2% and a UL94 rating of V0 for specimens of 2.5 mm thickness were achieved. Cone calorimeter results show a significant reduction of 39% in peak heat release rate (pHRR) compared to a benchmark flame‐retardant system, significantly enhancing flame‐retardant properties over existing systems across all assessed metrics. Highlights The intumescent flame‐retardant system was successfully manufactured in PBF. Energy density during manufacturing shows a limited impact on part properties. MnO effectively catalyzes the flame retardant reaction of the samples. V0 rating in ignition tests demonstrates the efficiency of intumescent mixture. Total heat released and pHRR significantly reduced due to highly effective barrier formation.

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