Abstract
Multi-walled carbon nanotubes (CNTs) as nano-reinforcements were introduced to facilitate the laser sintering process and enhance the thermal and mechanical properties of polymeric composites. A dual experimental-theoretical method was proposed to evaluate the processability and predict the process parameters of newly developed CNT-coated polyamide 12 (CNTs/PA12) powders. The thermal conductivity, melt viscosity, phase transition and temperature-dependent density and heat capacity of PA12 and CNTs/PA12 powders were characterized for material evaluation. The composite powders exhibited improved heat conduction and heat absorption compared with virgin polymer powders, and the stable sintering range of composite powders was extended and found to be favourable for the sintering process. The microstructures of sintered composites revealed that the CNTs remained at the powder boundaries and formed network architectures, which instantaneously induced the significant enhancements in tensile strength, elongation at break and toughness without sacrificing tensile modulus.
Highlights
Additive manufacturing (AM) techniques are a collection of advanced layer-by-layer processes which produce physical three-dimensional (3D) objects directly from the pre-programmed and slicedLaser sintering, or selective laser sintering (SLS), is one of the most established powder-based AM processes [4,5,6]
Evaluation of carbon nanotubes (CNTs)/PA12 for SLS Compared with PA12
The size and morphology of composite powders were investigated (Figure 2), and the particle size was mainly distributed within a narrow range of 60–70 μm, which is consistent with that of the neat PA12 (PA2200) as reported in the literature [25,26]
Summary
Selective laser sintering (SLS), is one of the most established powder-based AM processes [4,5,6]. The principal advantage of SLS is the ability to create complex geometries, compared with the conventional processes, such as cutting, tooling and moulding. The cost for the post-process of SLS is greatly lower than that of other types of AM techniques, such as selective laser melting [7,8], stereolithography and inkjet printing [9,10,11]. A large number of thermoplastic powders can be enabled to be processed using laser sintering. Few polymers are commercially available for laser sintering, whereas hundreds of grades are available for conventional manufacturing techniques, such as injection moulding [12,13]
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