High-potential electrode

Sample cells (Figure 5.16) were constructed upon the coated panels by glueing the polished end of glass tubes (internal diameter about 50 mm.) onto the coated surface with epoxy cement. The sample cells were stored at 22 2°C and a relative humidity of 55 + 5 per cent. The steel panel served as high potential electrode (H), and a mercury electrode, connected by a platinum wire, as low potential electrode (L). Guarding was achieved by using a bell-shaped brass cover which also supports the connector of the low potential electrode. 

The Ki-value determinations were performed on coils with a diameter of about 0.2 m., made of cable samples with a length of about 10 m. Such a coil is immersed in an (electrically insulated) water-bath filled with tapwater and kept at the specified temperature. The electrical resistance is then measured between the copper wire of the cable (high potential electrode) and the tapwater (low potential electrode). The Ki-value is calculated according to [29] ... 

An example of a PVC orientation depolarisation effect, measured with a combined TMA/TSD system is given in chapter 6. These orientation depolarisation effects were measured on small (i.e. 8 mm.) diameter, samples. Such samples proved to be too small, however, to detect the space charge depolarisation effects in non-polar SSBR rubbers. These non-vulcanised rubber samples were pressed, therefore, at 140°C between two (l mm thick) brass disks with a diameter of respectively 110 mm (high potential electrode) and 80 mm (low potential electrode) to a sample thickness of about 0.2 mm. A ring (inner/outer diameter 75/85 mm) of 50 micron thick Vespel foil avoided shortcircuiting between the two brass disks. 

Desorp(ion Field desorption (FD) High-potential electrode... 

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