Relationships between Processing Parameters and the Foaming Performances of Polyethylene for Coaxial Cable Insulation

Coaxial cable is cable that transmits electrical energy and signal from the receiver devices to the antenna in the base station. Nowadays, as the telecommunication technology develops, demand for a high signal quality is required in the coaxial cable. In this cable, the electromagnetic signal passes through the insulation, which is usually composed of foamed high-density polyethylene (HDPE)/low-density polyethylene (LDPE) blend. To improve the dielectric properties of insulation and reduce the signal power loss (attenuation), it is necessary to increase the foaming rate of insulation. In this study, two types of foaming experiments were performed: batch type foaming and continuous extrusion foaming. The relationship between the foaming rate and the electrical properties of insulation was investigated in the batch type foaming process. Also, the effects of processing conditions, such as resin composition, die temperature, screw speed, and pressure drop rate of die on the foaming performances were studied in the continuous foaming extrusion for coaxial cable insulation.