Polyurethane Chemorheological Analysis for In Situ Ambient Reactive Extrusion Additive Manufacturing

Author(s):

Alice Savage, Aynslie J. Fritz, Nicholas Enos, Jeffrey Wiggins, Ian McAninch, and E. Jason Robinette

Abstract:

A parallel study of polyurethane (PU) chemorheological properties and their subsequent 3D printing via ambient reactive extrusion (ARE) additive manufacturing (AM) is reported. PU modularity makes them promising feedstock for ARE, thus the chemorheological properties of PUs with systematically increased concentrations of fumed silica (FS) were evaluated. Unfilled PUs displayed the longest gel time (51 min), while increasing FS concentration decreased gel time to 16–28 min. The first PUs printed via ARE in available open literature were demonstrated with 5.0 wt% FS PUs, where printed specimens agreed with intended geometry and achieved vertical heights exceeding 25 mm. Cross-sectional analysis via optical microscopy and scanning electron microscopy revealed coalescence of deposited layers with no distinct interfaces. Specimen were post-cured at 160 °C for 2 h, where hard segment glass transition temperature was observed to increase from 67.9 to 74.1 °C. The unique simultaneous synthesis and 3D printing strategy utilized in this research combined chemorheological analysis and successful PU print demonstrations to establish an ARE platform for further reactive materials and 3D printing applications.