In a cable coating process, in which the cable is coated with chemically-foamed resin, the electrical and physical properties of the insulated cable rely on the porosity in the foamed resin as well as the average bubble size. Experiments elucidated that the porosity and the bubble size were mainly determined by two key factors, namely, the gas quantity produced by decomposition of the foaming agent and the amount of the unreacted foaming agent. This paper proposes a mass balance model that can quantitatively describe the correlation between the two factors and the operating conditions (barrel temperature, foaming agent mixing ratio, and so on). The developed model leads to an optimal operating region in which good products (high porosity, small bubble size) can be produced.

View full abstract