Extrusion‐printing additive manufacturing of composite solid propellant by fast curing isocyanated‐HTPB and HTPB blending‐extruded via a static mixer

Abstract

This article studied a novel method for extrusion‐printing additive manufacturing (AM) of composite solid propellant by fast curing isocyanated‐HTPB and HTPB, which were blended and extruded via a static mixer. The gel time and tack‐free time of isocyanated‐HTPB with HTPB or diamines were extensively studied to screen for the potential formulation of extrusion‐printing. Upon the results of computational fluid dynamics simulation on the mixing effect of the static mixer, the formulation with 7 min gel time and 2.5 h tack‐free time was selected for extrusion‐printing experiment. The shape retaining characteristic of the formulations with 72 wt %, 75 wt %, 80 wt %, and 85 wt % solid content was qualitatively studied by printing the points, fibers, fiber arrays, and multilayer samples under fixed printing parameters, such as the slurry flux, the nozzle moving speed, and air pressure etc. The results showed that the curing rate and solid content play an important role in the free standing property of the slurry printed. A 3D sample with a complex geometric shape, which has 15 layers,18.5 mm in height, and 20.1 mm in outer diameter, was successfully extrusion‐printed by fast curing the slurry with the formulation of 85 wt % solid content. Its tensile strength and elongation at break are 0.33 MPa and 39.9 %, respectively. SEM observation showed that the internal morphology of the sample printed is dense and uniform. The results demonstrated that extrusion‐printing AM by fast curing two components is a potential candidate AM method for composite solid propellants with high solid content.