Journal of Microwave Power and Electromagnetic Energy (JMPEE)
TITLE	Permittivity Measurement of Thermoplastic Composites at Elevated Temperature [PDF]
AUTHORS	H.S. Ku, B. Horsfield, J.A.R. Ball and E. Siores 2001 36 2 101-111
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Abstract The material properties of greatest importance in microwave processing of a dielectric are the complex relative permittivity ε = ε’- jε”, and the loss tangent, tan δ = ε”/ ε’. This paper describes two convenient laboratory based methods to obtain ε’, ε”, and hence tan δ of fiber-reinforced thermoplastic (FRTP) composite. One method employs a microwave network analyzer in conjunction with a waveguide transmission technique, chosen because it provides the widest possible frequency range with high accuracy. The values of the dielectric constant and dielectric loss of glass fiber reinforced (33%) low density polyethylene LDPE/GF (33%), polystyrene, PS/GF (33%), and Nylon 66/GF (33%) were obtained. Results are compared with those obtained by another method suing a high-temperature dielectric probe. Key Words: Complex relative permittivity, loss tangent, waveguide transmission technique, dielectric probe.