I. Introduction
In wood-based composite manufacturing, a thermosetting resin system was commonly used as a structural adhesive because, after curing, they typically show excellent dimensional stability, chemical corrosion resistance, and excellent thermal and mechanical properties [1],[2]. This curing can be done by heating energy from an oven or hot press to ensure the final product has good mechanical properties. If higher pressing time is used for curing, it may result in a higher degree of cure, but at the same time, it will increase energy costs and reduce production capacity [3]. To reach a balance between the performance of the composite panel and the cost of production, firms continuously strive to find an optimal pressing time. Generally, trial and error methods were used for optimizing the curing time, but this resulted in tedious work and didn't allow for getting information on real- time changes in the resin system. Therefore, real-time cure monitoring was needed, for which several techniques were developed, like acoustic methods, infrared spectroscopy, and dielectric spectroscopy [4]. Dielectric spectroscopy or dielectric analysis (DEA) is a widely used method to monitor the curing process of resins. When the resin undergoes cross-linking reaction, the material's dielectric property changes due to an increasing number of immobile groups that decrease the dielectric conductance [5],[6]. Various sensors such as parallel plates and interdigitated electrodes can be used for cure monitoring, providing the measurements in actual processing environments such as hot press, oven, and autoclave. In these dielectric measurements, the alternating current is measured by applying an alternating voltage between two electrodes in contact with a material. The material under test has ions and dipoles in it. Under the effect of the electrical field, ions move toward the electrode with the opposite polarity, whereas dipoles seek to orient with the electric field, and these changes provide information on the material's physical transitions and properties, including ion viscosity, reaction rate, and cure state. [5]. Many curing studies using dielectric studies were published for epoxy resin [7],[8], urea-formaldehyde resin [5], melamine formaldehyde resin [6], and phenol-formaldehyde resin [9].