Exploiting refractometry to estimate the density of polyethylene: The Lorentz–Lorenz approach re-visited

The Lorentz–Lorenz equation is a fundamentally sound theoretical equation that relates refractive index and density. In this study, refractive index measurements were used in combination with the Lorentz–Lorenz equation to determine the density of various polyethylene specimens. Excellent agreement was observed between the specimen density calculated from the Lorentz–Lorenz equation and as measured using a density gradient column. Further, calculating polyethylene density from refractometry experiments using a Metricon Prism Coupling device was noted to be more accurate, more reproducible, simpler and consumes far less time compared to the traditional density gradient column technique.