<title>Continuous monitoring of the progressive degradation of a liquid composite by means of a noninvasive microwave resonator</title>

Abstract

Microwave control capabilities have been used to monitor the degradation of poiyoi, an alcohol composite material commonly used in the footwear industry for polymerization purposes. The liquid flows continuously inside a thin pipe and its desirable properties are altered with time associated to moisture absorption processes. Consequently, variations in the dielectric properties are involved, and they can be detected by permittivity measurements. In this paper, in order to obtain high sensitivity and resolution, a rectangular cavity resonator working at a fixed frequency was designed using as sample holder a rectangular pipe containing the liquid going through. Changes in the liquid modify the original response of the cavity with a non-degraded liquid and these differences have been used to determine the degree of degradation of the material. The final response of the microwave resonator was experimentally validated with measurements in a continuous line.