Rheology and 3D Printability of Percolated Graphene-Polyamide-6 Composites

• Published in: Polymers Vol. 12; no. 9; p. 2014
• Main Authors: Lee, Kok Peng Marcian, Brandt, Milan, Shanks, Robert, Daver, Fugen
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 03.09.2020; MDPI
• Subjects: 3-D printers; 3D printing; Additive manufacturing; Extrusion; Filaments; Graphene; material extrusion; Nozzles; Percolation; Polyamide resins; Polymer matrix composites; Polymer melts; printing envelope; Raw materials; Rheological properties; Rheology; Rheometry; Shear; Shear thinning (liquids); Three dimensional models; Three dimensional printing; Viscosity; United States > US; printing envelope; material extrusion; rheological properties; 3D printing; graphene
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym12092014

Graphene-polyamide-6 (PA6) composites with up to 17.0%· / graphene content were prepared via melt mixing. Oscillatory rheometry revealed that the dynamic viscoelastic properties of PA6 decreased with the addition of 0.1%· / graphene but increased when the graphene content was increased to 6.0%· / and higher. Further analysis indicated that the rheological percolation threshold was between 6.0 and 10.0%· / graphene. The Carreau-Yasuda model was used to describe the complex viscosity of the materials. Capillary rheometry was applied to assess the steady shear rheology of neat PA6 and the 17.0%· / graphene-PA6 composite. High material viscosity at low shear rates coupled with intense shear-thinning in the composite highlighted the importance of selecting the appropriate rheological characterisation methods, shear rates and rheological models when assessing the 3D printability of percolated graphene-polymer composites for material extrusion (ME). A method to predict the printability of an ME filament feedstock, based on fundamental equations describing material flow through the printer nozzle, in the form of a printing envelope, was developed and verified experimentally. It was found that designing filaments with steady shear viscosities of approximately 15% of the maximum printable viscosity for the desired printing conditions will be advantageous for easy ME processing.