Migration and leakage of some mobile components in rocket propellant produces an inhomogeneous composition region at which migration takes place, which can lead to premature detonation, changes in ballistic characteristics, and so on. It is, therefore, important to be able to predict the behavior of low-molecular-weight mobile additives and to control the leakage of them from the propellant. At this point, our chief interest was to study the magnitude of the migration and to understand the factors that influence the migration process. In this study, the migration of a ferrocene-based burning-rate catalyst [acetyl ferrocene (AcF)] a from hydroxyl-terminated polybutadiene (HTPB) based elastomer in the presence of a plasticizer (dioctyl adipate) was examined in accelerated aging conditions at 60°C for various time intervals. We also tried to minimize the migration of AcF from the loaded to the unloaded part by using an extra barrier layer consisting of polyfunctional aziridine (AST D45ϩ) in addition to the HTPB-toluene diisocyanate composition. The migration enhanced with aging of the AcF and the barrier effects of the layer with intensified crosslink density to this migration were studied extensively. The migration was monitored by both ultraviolet-visible and atomic absorption spectroscopy (AAS) methods. A comparison of the data obtained from both of these methods was also done. The two techniques were found to be in agreement, and the Fe determinations from both methods were highly correlated, suggesting that the data were reliable, although the AAS data were found to be symmetrically somewhat higher.

ABSTRACT:In composite solid propellants, low-molecular-weight species such as burning rate catalysts, plasticizer, etc. which migrate into liner and thermal insulation layers during curing and storage invariably result in poor mechanical and ballistic properties of the propellants. In the present study, the migration of the burning rate catalyst, acetyl ferrocene, was investigated spectrophotometrically (UV-visible) by evaluating the extent of hindrance to such migration after applying a barrier (liner) of various crosslink densities between the additive (HTPB-TDI-plasticizer-acetyl ferrocene) and nonadditive (HTPB-TDI) gumstocks replicating the propellant and insulating layer, respectively. Enhancing the crosslink densities of liner via a trifunctional aziridine crosslinking agent inhibited migration. The aging of additive gumstock was done at 60°C and its mechanical properties and extent of acetyl ferrocene migration were also evaluated and analyzed.

The radio-frequency plasma-initiated polymerization of N-isopropylacrylamide (NIPAM) in the solid state was performed. The isolated linear polymer was characterized by 13 C-NMR, 1 H-NMR, and Fourier transform infrared spectroscopy, and the effects of selected operational plasma parameters (discharge power and time) on the conversion rates were studied. Reversible transitions at the volume-phase-transition temperatures of the swelled poly(N-isopropylacrylamide) hydrogels were investigated by differential scanning calorimetry. The surface morphologies before and after plasma treatment were followed by scanning electron microscopy. With the obtained X-ray diffraction results, we propose a solid-state plasma polymerization mechanism for the NIPAM.