Refractometry

Abstract

Polymers are an integral part of our everyday life as they are used in products from clothing to car dashboards, toys to aircraft wings, and hundreds of other products that reflect their high strength, low weight, and manufacturing versatility. To use polymers most efficiently, knowledge of both their processed structure and how that structure affects their performance is required. The processed structure signifies either the molecular orientation in a single‐phase polymer system or the amount and orientation of each phase in a multiphase polymer. One particularly useful and simple technique for quantifying the structural state of a polymer sample is polarized refractometry using an Abbe refractometer. This technique is important because it is nondestructive, inexpensive, simple to use, easy to understand, and generates considerable information about the structural state of the polymer. A partial list of the structural information derivable from the refractive index(es) measured with an Abbe refractometer using polarized monochromatic light includes the three principal refractive indexes ( N x , N y , and N z ), axiality (isotropic, uniaxial, multiaxial), average refractive index, density, crystallinity, molecular weight, glass‐transition temperature, copolymer composition, and three‐dimensional molecular orientation. This article presents the theory and practical aspects of polarized refractometry along with applications to real polymer systems.