Electrical Properties of Plastics
  Plastics, as used in various areas of electric industry, from a small product casings and wire coverings to a large electric good housings, are normally possess somewhat degree of electrical insulation property. Performance may be evaluated with respect to electrical track resistance, ability to resist ignition from electrical sources and other electrical properties as follows. In order to avoid an excessive level of implied precision and bias, material performances for several tests are recorded as Performance Level Categories (PLC), based on the mean test results (rather than recording the exact numerical results).
Electrical Property and Test Methods
  HWI (Hot Wire Ignition) / UL746A
The time elapsed for a specimen to ignite when it is wrapped with a wire of specific resistance and connected to a specific voltage.
 
HWI (Sec.) PCL Grade
More than 120sec. 0
60 ¡­120sec. 1
30 ¡­ 60sec. 2
15 ¡­ 30sec. 3
7 ¡­ 15sec. 4
Less then 7sec. 5
  HAI (High Current Arc Ignition)
Resistance to an ignition when an insulating material is in contact with an arc; the number of arcs produced (at 40 arcs/ min.) before ignition, under high current and low voltage.
 
H A I PCL Grade
More than 120 times 0
60 ¡­120 times 1
30 ¡­ 60 times 2
15 ¡­ 30 times 3
7 ¡­ 15 times 4
  HVTR (High Voltage Arc Tracking Rate)
Capability of an insulating material to stand without forming a conductive path with high current and voltage flowing on its surface; path forming speed (the length of the path formed per a unit time under a high voltage (5200V))
 
HVTR(mm/min) PCL Grade
0 ¡­10 mm/min 0
10 ¡­25 mm/min 1
25 ¡­ 80 mm/min 2
80 ¡­ 150 mm/min 3
More than 150 mm/min 4
  Arc Resistance
Number of seconds that a material resists the formation of a surface conducting path when subjected to an intermittently occurring arc of high voltage, low current characteristics.
 
Average time (sec.) PCL Grade
More than 420 sec. 0
360 ¡­420 sec. 1
300 ¡­ 360 sec. 2
240 ¡­ 300 sec. 3
180 ¡­ 240 sec. 4
120 ¡­ 180 sec. 5
60 ¡­ 120 sec. 6
Less than 60 sec. 7
  Comparative Tracking Index (CTI)
Voltage- endurance when the product is contaminated. A material with a high value of the CTI can be a superior insulator in an easily contaminating environment. CTI is the voltage, which causes a track after 50 drops of 0.1percent ammonium chloride solution have fallen on the surface of the material.
 
CTI(Volt) PCL Grade
Higher than 600 volt 0
400 ¡­600 volt 1
250 ¡­ 400 volt 2
175 ¡­ 250 volt 3
100 ¡­ 175 volt 4
Lower than 100 volt 5
Dielectric Strength
Maximum voltage that an insulating material can possibly endure is measured. Measurement takes in place before the breakdown of the insulating material.

Volume Resistivity
The ratio of the direct voltage applied across electrodes in contact with or imbedded in an insulating material to that portion of the current between them.

Surface Resistivity
Level of resistance is measured between two electrodes that are on the surface of the insulating material. The ratio of the direct voltage applied on the electrode to the current is measured.