TDI addition sequence in the propellant production process and parameters for scale down/up

This paper discusses the castability, mixed viscoelasticity and voids of the propellant based AP/HTPB/TDI with HTPB-TDI binders. Several influential variables were observed including the plasticizer and the order in which the curing agent was added. Then the mixer used is also horizontal and planetary (vertical) mixers in order to obtain the scale up or scale down parameters between mixers. First experiment was mixed propellant formulation in a 5 kg horizontal sigma blade mixer, which was set up at 55°C and 60 rpm. The composition of propellant was 14% of HTPB, 7.5% of Al powder, 77.5% of AP with coarse, medium, fine ratio 1/1/1, and 1% of TDI. Propellant slurry as mixing product was casted into vacuum casting chamber then grained as desired, cured at 60°C for 2 days, was left in room temperature for a week. The propellant was X-Ray scanned and viscosity measurement at 3 rpm spindle speed. This experiment was repeated with the addition of TDI in the first sequence and the end sequence. The experiments were repeated with addition of DOA for 0.5 to 4%. The order of adding TDI in the propellant mixing process affects the viscoelasticity and castability of AP / HTPB / Al composite propellant. The mixing of the TDI at the end process will provide a better mixing space and evenly distributed particle distribution, is better applied to large rockets that require a longer treatment. Scale up and scale down of propellant mixers can use similarity while maintaining the same viscoelasticity and operating conditions. The addition of DOA increase pot life and viscoelasticity, but there are limitations to where the dough can be molded or processed. The maximum addition of DOA is 2.74% to produce a dough with an even distribution of particles with the added bonding agent.