Weibull statistical evaluation of the properties of 3D-printed nanographene-containing ABS

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., MatEx) 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 and interfilamentous adhesion of the filaments during printing. The ABS samples were thoroughly characterized for molecular weight, styrene, and acrylonitrile (AN) level, rubber content, and melt rheology. Scanning electron microscopy (SEM) revealed that the M5 nanoplatelets were very well dispersed in the final specially fabricated filaments. A two parameter Weibull distribution was used to quantify failure tendency and part lifetime. To this end, tensile bars were 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. Two 3D printing patterns (0 deg. axial and 45-45 deg. bead raster angles) were selected to determine their influences on the Weibull analyses of 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 45 - 45 raster angle printing configuration resulted in an increase in Weibull reliability.