ABSTRACT
Microwave sensors, which allow determining the dielectric properties of materials, have found industrial and scientific applications in the nondestructive testing of materials, identification of surface defects, spectroscopy and medical diagnosis. Their applicability in industrial process monitoring tasks has allowed new control functionalities, which directly improve the efficiency in the use of resources and, thus, the overall competitiveness. This chapter presents an example of microwave sensor system developed for the non-invasive monitoring of the curing process of thermoset materials. The practical nature of monitoring applications has forced researchers to develop microwave equipment according to industrial conditions, simple, affordable and robust, while retaining the necessary accuracy. In many industrial processes, it is very important to control the state of liquid components to ensure the final product quality. For instance, polyol is a highly reactive basic monomer commonly used for obtaining polymers in the footwear industry. It tends to absorb water, thus modifying the proper stoichiometric relationship in the reaction.
