Plasma-etched nanoclay-reinforced Polyamide 12 (PA12) powder is prepared with its intended use in selective laser sintering (LS) applications. To replicate the LS process we present a downward heat sintering (DHS) process, carried out in a hot press, to fabricate tensile test specimens from the composite powders. The DHS parameters are optimized through hot stage microscopy, which reveal that the etched clay (EC)-based PA12 (EC/PA12) nanocomposite powder melts at a temperature 2°C higher than that of neat PA12, and 1-3°C lower than that of the nonetched clay-based nanocompsite (NEC/PA12 composite). We show that these temperature differences are critical to successful LS. The distribution of EC and NEC onto PA12 is investigated by scanning electron microscopy (SEM). SEM images show clearly that the plasma treatment prevents the micron-scale aggregation of the nanoclay, resulting in an improved elastic modulus of EC/PA12 when compared with neat PA12 and NEC/PA12. Moreover, the reduction in elongation at break for EC/PA12 is less pronounced than for NEC/PA12.
Polyamide 12 (PA12) powder was exposed for up to 3 h to low pressure air plasma treatment (LP‐PT) and several minutes by two different atmospheric pressure plasma jets (APPJ) i.e., kINPen (K‐APPJ) and Hairline (H‐APPJ). The chemical and physical changes resulting from LP‐PT were observed by a combination of Scanning Electron Microscopy (SEM), Hot Stage Microscopy (HSM) and Fourier transform infrared spectroscopy (FTIR), which demonstrated significant changes between the plasma treated and untreated PA12 powders. PA12 exposed to LP‐PT showed an increase in wettability, was relatively porous, and possessed a higher density, which resulted from the surface functionalization and materials removal during the plasma exposure. However, it showed poor melt behavior under heating conditions typical for Laser Sintering. In contrast, brief PJ treatments demonstrated similar changes in porosity, but crucially, retained the favorable melt characteristics of PA12 powder.
Front Cover: Low pressure plasma treatment and atmospheric pressure plasma jets were applied for the surface modification of Polyamide 12 powder (PA12, bottom) used in Laser Sintering. Different treatment times (middle) and plasma sources (kINPen® IND, top; Hairline, and Zepto) were used. Low pressure plasma treated PA12 showed an increase in wettability, powder porosity, and possessed a higher density resulting in poor melting behavior for treatment times of up to 3h. Brief atmospheric pressure plasma (several minutes) treatments demonstrated similar changes in contouring and deepening of morphological features as observed by low voltage scanning electron microscopy, but crucially, the short atmospheric pressure plasma treatment with Hairline retained the favorable melt characteristics of PA12 powder.
Further details can be found in the article by Alaa Almansoori et al. (http://doi.wiley.com/10.1002/ppap.201800032).
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