Temperature modulated optical refractometry: A novel and practical approach on curing and thermal transitions characterizations of epoxy resins

Abstract

Abstract Chemically induced glass transition and shrinkage during polymer curing are often disregarded, albeit their strong effect on cohesion and organization of solid-state matter. One strategy to access these features is the acquisition of the static and dynamic volume expansion coefficients. “Temperature Modulated Optical Refractometry” (TMOR) is a novel and purely thermo-optical analysis technique that allows the time or temperature evolution of both properties. With the aid of TMOR, the curing kinetics of an epoxy resin, including the inherent chemically induced glass transition and shrinkage, was investigated in this work. Shrinkage of an epoxy resin, as function of refractive index changes, was measured for the first time. Afterwards, dynamic thermal coefficients and shrinkage, verified at different time intervals, revealed the hindrance of molecular self-diffusion at the late curing stage. In addition, TMOR results were compared with rheological measurements, and yielded new insights into curing kinetics of an epoxy.