Characterization of Various Materials Using Refractometry
Refractive index (RI) is a fundamental physical property of a material. However, the RI values of several binders, including nitroplasticizer (NP), Estanes, and KelF/FK 800, are not available in literature. Further, their temperature dependencies are undocumented either. In this study, we have developed a set of methodologies to accurately and effectively determine the RIs of these binder materials between 20 and 70°C. The RIs of these binders without aging show linear correlations with temperature, as shown in the figure below. Among these materials, Estane 5714 has the highest RI whereas FK800 has the lowest RI. As materials age, the changes in their RIs are different, suggesting different aging behavior of these binders upon heating. Typically, NP and Estane degraded through hydrolysis give lower RIs than the baseline materials. However, when KelF/FK800 materials thermally age, their RIs increase. Overall, this study demonstrates refractometry is a sensitive technique to detect aging signs in various materials of interest.