Effect of porophor content on the useful properties of external coatings
of cables obtained by foaming extrusion
Basing on the literature data the process of foaming extrusion was discussed in details including the types of extrusion heads used (Fig. 1-5) and porophors used in the process, with their decomposition characteristics. Using modernized technological line for coating extrusion, containing a vacuum-pressure calibrator of own construction (Fig. 6-8), the external PVC coatings of electrical power cables, with porous core and solid surface, were prepared in steady-state conditions. The mixture of sodium bicarbonate and citric acid, in the amount up to 1 wt. % per polymer, was used as blowing agent showing endothermic course of decomposition. It was shown that in this range of porophor content the external coatings showed good useful properties (porosity degree, density, and mechanical strength - Table 2 and 3).
Key words: foaming extrusion, extrusion heads, calibrators, porophors, electrical power cables, external coatings, poly(vinyl chloride), useful properties
T. Garbacz, A. Tor
Effect of porophor content on the useful properties of external coatings of cables obtained by foaming extrusion