Multi-objective optimization of coaxial cables with foamed LDPE/HDPE dielectric layers: Correlating process parameters with foam structure and impact on piezoelectric and electrical properties

Polymeric foams are one of the new candidates for use in the dielectric layer of coaxial cables to improve their piezoelectric and electrical properties. These properties are affected by the structural properties, which depend on material and processing parameters. In this research study, first, the effect of cell size, cell density, and expansion ratio was theoretically studied on the piezoelectric and electrical properties. Then the effect of talc content, processing temperature, and cooling method was investigated on the structural, piezoelectric, and electrical properties of the produced coaxial cables. The examinations revealed that the increase in cell size, cell density, and expansion ratio increases the piezoelectric coefficient and velocity of propagation and decreases attenuation. According to the analysis of variance results, the talc content parameter was the most effective parameter on cell size, cell density, and piezoelectric coefficient with the contribution of 72%, 83%, and 69%, respectively. Also, the processing temperature parameter was the most effective parameter on the expansion ratio and electrical properties with the contribution of 42%, and 41%, respectively. Finally, the produced sample with talc content of 2 wt%, processing temperature of 125 degrees C, and cooling method by water was introduced as the optimum sample by the multi-objective optimization.Highlights Production of foamed dielectric layers in extrusion process of coaxial cables. Effect of cell structure on piezoelectric and electrical properties. Effect of process on structural, piezoelectric and electrical properties. Optimization of structural, piezoelectric, and electrical properties. Optimum conditions: 2 wt% of talc, temperature of 125 degrees C, and water cooling.