Volume 2, Issue 6 (June 2005)
The Effect of Ammonium Nitrate, Coarse/Fine Ammonium Nitrate Ratio, Plasticizer, Bonding Agent, and Fe2O3 Content on Ballistic and Mechanical Properties of Hydroxyl Terminated Polybutadiene Based Composite Propellants Containing 20 % AP
It was aimed to develop the HTPB (hydroxyl terminated polybutadiene) based composite solid propellant with reduced smoke in acceptable mechanical and ballistic properties by using AN (ammonium nitrate) and AP (ammonium perchlorate) as oxidizing agents. For this reason, five different combinations, employed by increasing the AN content as 33, 43, 53, 63, and 73 % and decreasing the AP content as 40, 30, 20, 10, and 0 % were used. The propellant containing 20 % AP and 53 % AN was selected to have good processability and lower smoke content among five compositions.
The content of DOA (dioctyl adipate) used as a plasticizer was varied between 35 % and 25 % of HTPB binder to improve the mechanical properties with taking the above composition as a reference. In decreasing the DOA content, mechanical properties could not be improved to the desired level, and the amount of the bonding agent TEPANOL (tetraethylene pentamineacrylonitrileglycidol) was increased from 0.2 % to 0.35 mass percent with keeping DOA content at the level of 25 % of HTPB binder. 0.495 N/mm2 maximum tensile stress and 25.5 % elongation at maximum tensile stress and 3.635 N/mm2 elastic modulus values were then obtained with 0.35 % TEPANOL value.
The effect of coarse/fine AN ratio on buring rate of the propellant was also tested for three different ratios, i.e., 80/20, 70/30, and 60/40. The 70/30 ratio gave the highest burning rate. Then, the content of burning rate catalyst Fe2O3 (iron oxide) was varied between 2 % and 1.0 % with keeping the coarse/fine AN ratio at 70/30, and it was found that 2 % Fe2O3 gave the highest burning rate.
Values of densities and heat of explosion were also determined for all compositions tested.