Abstract
Abstract This paper proposes two methods of preparation of graphene/PEEK powders for Laser Sintering (LS) and investigates their behaviour in relation to their microstructure and their properties. Thin composite films were fabricated in an attempt to replicate the thin layer formation of the powder bed process. Both methods of composite powder preparation (wet and dry) led to enhanced mechanical performance of the composite films at 0.1 and 0.5 wt% graphene nano-platelets (GNP) concentrations. The TEM images show that the GNP act as a nucleation point in crystallisation of PEEK, being at the centre of the spherulites. The hot stage microscopy reveals a 20 s delay in the onset of GNP/PEEK nanocomposite coalescence in comparison with plain PEEK. This is a very important observation for laser sintering, as it will influence the build strategy and specific parameters (e.g. time between layers deposition, multiple exposures). The excellent electrical conductivity properties of graphene were noticeable in the nanocomposite films at concentrations above 1 wt% GNP.
Highlights
As more polymeric materials are being developed for powder bed additive manufacturing [1, 2], the interest in multi-functionality through the addition of various fillers and nanoparticles is growing
It is shown that graphene nano-platelets (GNP) is well dispersed amongst the PEEK particles under lower GNP weight percentage (0.1 and 1 wt%), but GNP tends to aggregate under higher concentrations (e.g. 10 wt%)
This paper presented two potentially cost effective preparation methods of GNP/PEEK powders
Summary
As more polymeric materials are being developed for powder bed additive manufacturing [1, 2], the interest in multi-functionality through the addition of various fillers and nanoparticles is growing. The authors found that their cryogenic milling method could not produce powders with suitable morphology for laser sintering [10] High performance materials such as Polysulfone (PSU) and Polyether ether ketone (PEEK) have been investigated and it was shown that it is possible to mill these materials to fine powders [8, 14]. The rotary milling produced PEEK powders with superior properties in comparison with the disc milling method This strategy of melt compounding followed by milling, is highly energy intensive and can become costly. In some cases, excessive processing of the materials (either the polymer or the nanoparticle) can lead to changes in their structure and ultimate performance For these reasons, the present study is investigating the performance of graphene/PEEK composite powders through a dry and wet method with minimum impact on the raw materials. The materials exhibited enhanced mechanical properties with a limited amount of MWCNTs (1.70 %wt) [20]
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