Shape and size effect of octogen and hexogen particles modified by PU coating to their processibility of composite propellant.

Shape and size improvement of the hexogen (RDX) and octogen (HMX) particles and their effect on the processibility and hardness of the propellants have been carried out with polyurethane-based HTPB (PU-HTPB) coating and washing treatment. Both RDX and HMX were coated by the solution coating method. A total of 200 grams of RDX and HMX were mixed with a solution of Hydroxyl-Terminated Polybutadiene/toluene diisocyanate (HTPB/TDI) with a weight ratio of 14/1 and a concentration of 2 mL/200mL of ethyl acetate, stirred for 20 minutes, filtered, and dried in an oven for a week at 60oC. RDX and HMX were treated with no washing, one-time washing, and three-times washing with alcohol. RDX and HMX coatings can increase particle size. A 20% increase in particle size improves the propellant slurry's viscosity by 13.824%. Washing coated RDX or HMX can improve the particle's shape. One-time washing changes the roundness up to 8.157%, deflating the surface area up to 57.064%, thereby reducing the viscosity of the propellant slurry by 13.824%. Moreover, increasing the washing up to three times decreases the roundness and viscosity of the propellant slurry by 23.521%. In general, the propellant slurry can still be processed using the vacuum casting method, and the slurry viscosity is still below 20,000 Poise. The average viscosity of the HMX propellant slurry is higher than that of RDX. Based on the optimization results, optimal RDX and HMX are obtained by using RDX coating with PU-HTPB and one-time washing so that there is a slight change in particle size (less than 5%), giving better roundness, resulting in a decrease at the end of mixing (EOM) viscosity of 28.127%, and better propellant processability. The hardness analysis of cured propellant supports this statement. The hardness characterization shows a similar trend to the viscosity of the slurry propellant. [ABSTRACT FROM AUTHOR]