Characterisation of the dielectric properties of rubber latex from 0.5 to 33 GHz

• Dielectric properties determined from 10 to 40 °C for different dry rubber contents.
• Double relaxation process exists in rubber latex.
• Extended Debye equation proposed to model dielectric permittivity.

This paper presents a detailed characterisation of the dielectric properties of rubber latex over the entire microwave frequency range (0.5–33 GHz), for samples with a range of dry rubber contents and over the temperature range 10–40 °C. The relaxation processes observed are analysed and compared to pure water, as modelled with the Debye equation. It is shown that two relaxation processes exist in rubber latex, with one of these attributed to the presence of bound water molecules. The extended Debye equation is then applied to model the dielectric permittivity. Each relaxation time extracted from the modelling exposes a different physical mechanism in rubber latex. It is believed that this is the most extensive study of the microwave properties of rubber latex yet reported, and that the results are an important step in the development of microwave sensors for determining the quality of rubber latex for agriculture and industrial application.