Novel Acrylonitrile Butadiene Styrene (ABS) polymers melt-blended with 5 wt.% and 10 wt.% XGnP™ M5 graphene nanoplatelets were fabricated into 1.75 mm diameter filament for 3D printing (i.e., Mat.Ex.) in order to determine how the strength and toughness of 3D-printed ABS may be affected by M5 addition. An ABS with a bimodal molecular weight distribution (MWD) with a prominent portion of the distribution at the low MW end was selected with the intention to foster early stage molecular interpenetration between and interfilamentous adhesion of the printed filaments. The ABS samples were thoroughly characterized for molecular weight, styrene and acrylonitrile (AN) levels (via 13C NMR), rubber content (via 1H NMR), and melt rheology. Accessible print speed was limited by melt viscosity of the melt blends. Scanning electron microscopy (SEM) revealed that the M5 nanoplatelets were very well dispersed in the final specially fabricated filaments. 3D printing patterns (0o axial and 45o-45o bead raster angles) were selected in order to determine their influences on toughness, tensile and dynamic mechanical properties. Toughness was halved with each 5 wt.% addition of graphene, while tensile modulus roughly doubled with increasing graphene content from 0 wt.% to 10 wt.% M5. The 45o-45o 3D printing configuration affected little change in notched Izod impact toughness vs. the 0o axial raster angle printing configuration. Test bars fabricated to an ASTM-compliant shape by 3D printing were compared with analogous bars milled to the identical shape to measure the differences in the resulting physical properties. Generally, the properties for print-to-shape tensile samples were found to be inferior to the milled-to-shape equivalents due to circumferential printing paths that formed planar weaknesses at the sample edges. A two parameter Weibull distribution was used to quantify failure tendency and lifetime. To this end, tensile bars were also fabricated each with a 3 mm diameter hole at its center to provide for a defined stress concentrator, and subsequently milled to the shape of ASTM tensile bars. Weibull analyses were performed on the tensile results. As reflected in the Weibull moduli, graphene additions resulted in a decrease in reliability, whereas the defined hole geometry and the use of a 45o- 45o raster angle printing configuration resulted in an increase in reliability.

3D printing and Weibull statistical evaluations of nanographene-containing ABS thermoplastics

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.