Technical Information|Electrical Properties|Tracking Properties

Tracking breakdown refers to the formation of tracking (a conducting carbonized path) on either or both of the surface and the inside of a molded product due to the combined action of the electrical field and electrolyte contamination, resulting in dielectric breakdown. To determine the tracking resistance, electrodes (an electrical field) are brought into contact with a flat plate shaped test piece and drops of electrolyte are put between those electrodes, such that the voltage that results in dielectric breakdown can be determined, as shown in the schematic diagram (Fig. 7.14). For the tracking properties, the comparative tracking index (CTI) is often used. In the UL standards, the breakdown voltage is classified into six classes (PLCs).

Fig. 7.14  Tracking resistance evaluation (schematic diagram)

Fig. 7.14 Tracking resistance evaluation (schematic diagram)

It is known that, in general, PPS is more likely to form a conducting carbonized path than nylon or polyester, and has a low tracking resistance. TORELINA A660MB is a grade that has a drastically improved tracking resistance, as it suppresses the formation of a conducting carbonized path. It has been assigned the highest rank (rank 0) of the UL standards. TORELINA A660EXB is a grade for which the mechanical strength has been enhanced to a level comparable to a general high-filler PPS, while maintaining its tracking resistance. (Table. 7.4)

Table. 7.4 Tracking resistance of TORELINA

Item Units GF + filler reinforced Tracking resistance grade
A310M A660MB A660EXB
Tracking resistance
(UL standard/PLC)
V Up to 250 600 >600
- Rank 3 Rank 0 Rank 0
Tensile strength MPa 115 80 110
Tensile elongation % 0.8 0.5 0.7
Flexural strength MPa 200 140 175