Rheology of concentrated AP/HTPB suspensions prepared at the upper limit of AP content

Due to the requirements for the preparation of an ammonium perchlorate (AP) /hydroxy-terminated polybutadiene (HTPB) based composite propellant, an upp er limit content of AP applicable in the propellant, phi(max) (wt%), exists . The rheology of concentrated AP/HTPB suspensions prepared at phi(max) iS investigated in this study. The relative viscosity, eta(r phi)(-), of the s uspensions prepared at cp,,, is almost constant at approximately 200. For t he suspensions prepared at cp,,, the HTPB layer thickness, H-phi p (mu m), on the AP particle, calculated from the specific surface area measured by t he air-permeability method, is closely related to the void fraction, epsilo n(max)(-), for the loose packing of the AP powder. H-phi p decreases with i ncreasing epsilon(max). By reversal conclusion it was found that the relati ve viscosity of the suspension, of which the HTPB layer thickness is H-phi p, will accordingly be eta(r phi).