PA11 Powder characterisation for composite tapeline processing

This study presents an application-specific, process-relevant screening methodology for evaluating commercially available PA11 powders intended for powder-based composite tape manufacturing. The methodology integrates particle size distribution (PSD) and morphology analysis, hygroscopicity measurements, and powder rheology to assess powder flow behaviour governing the upstream stages of the powder tapeline process. Two commercially available PA11 grades were investigated: Powder 1 (D50 ≈ 35 µm, additive-free) and Powder 2 (D50 ≈ 300 µm, plasticised). Intrinsic particle characteristics were evaluated via PSD and morphology analysis, moisture sensitivity using dynamic vapour sorption (DVS), and powder flow behaviour using an FT4 powder rheometer. Despite its coarser particle size and higher bulk permeability, which typically indicate lower powder cohesion, Powder 2 exhibited higher dynamic basic flow energy (141.72 mJ vs 115.55 mJ), greater shear cell cohesion (1.42 kPa vs 0.60 kPa), lower flow function coefficient (3.37 vs 7.60), increased aeration resistance, and greater moisture uptake (≈ 1.7 % vs ≈ 1.2 %) than Powder 1. Temperature-dependent DVS revealed reversible, surface-controlled adsorption for Powder 1, whereas Powder 2 displayed open-loop hysteresis and evidence of moisture-induced structural transitions. These results demonstrate that particle size alone is insufficient to explain the contrasting powder-flow behaviour of the two commercial PA11 grades, highlighting the need to consider particle characteristics, formulation and environmental sensitivity collectively. Powder 1 exhibited more stable rheological behaviour across humidity conditions, whereas Powder 2 showed cohesive characteristics that may compromise feeding reliability. The integrated methodology provides a characterisation framework for screening polymer powders for dry-processing composite tape manufacturing applications