Microscopic Investigation of Rocket Propellant Processing Parameters on Cure Shrinking

We have developed a unique tool based on Nuclear Magnetic Resonance (NMR) Imaging methods, for the study of the microscopic structure of polymer matrices. We believe that these methods are uniquely suited to the study of cure shrinkage and aging in rocket motor propellants, and we propose to work with DOD collaborators to demonstrate this capability and to employ our imaging methods in laboratory scale experiments aimed at assessing the degree of cure shrinkage and aging in test samples. In an ongoing study of propellant materials we have obtained images with an in plane resolution of 35 micrometer. Our methods reveal the spatial distribution of the HTPB binder material at a microscopic scale and provide a direct detection mechanism of voids, cracks and heterogeneity in the filler material, specifically the granularity of the solids loading. In addition the sensitivity of NMR imaging to residual dipolar couplings can be explored to study the effects of additives such as curatives and plasticizers and to detect the effects of aging.