UL 746A-2020 pdf free download

UL 746A-2020 pdf free download.Polymeric Materials – Short Term Property Evaluations.
21A.4 Testing is to be conducted in a medium that is appropriate for the material tested and in accordance with ASTM D 3755.
21A.5 A rate of rise of 500 Vlsec is to be used, unless an alternate rate of rise is found to be more appropnate for a specific matenal’s breakdown. The rate of rise is to be maintained constant throughout any given set of specimens, condatoned or unconditioned
22 D-C Resistance or Conductance of Insulating Materials
22.1 The test for the determination of the d-c resistance or conductance of insulating materials is
described in the Standard Test Methods for 0-C Resistance or Conductance of Insulating Materials. ASTM
D 257 (Dielectric and resistive properties of solid insulating materials — Part 3-3: Determination of resistive
properties (DC methods) — Insulation resistance, IEC 62631-3-3).
22.2 The Standard Test Methods for DC Resistance or Conductance of Insulating Materials, ASTM D
257 (Dielectric and resistive properties of solid insulating materials — Part 3-3: Determination of resistive properties (DC methods) — Insulation resistance, IEC 62631-3-3) cover procedures for the determination of d-c volume resistance, volume resistivity, surface resistance, and surface resistivity of electrical insulating materials. The test procedure in this standard specifically excludes the determination of insulation resistance as described within ASTM 0 257 (paragraph 12.1).
22.3 The test procedure for volume resistance or conductivity is described in paragraph 12.2 of the Standard Test Methods for DC Resistance or Conductance of Insulating Materials, ASTM 0 257 (Dielectric and resistive properties of solid insulating materials — Part 3-3: Determination of resistive properties (DC methods) — Insulation resistance. IEC 62631-3-3). Three specimens are to be tested following a conditioning of 48 hours at 23.0 ±2.0” C (73.4 ±3.6 F) and 50 ±10 percent relative humidity, and 3 specimens are to be tested following a conditioning of 96 hours at 35.0 ±1.0C (95.0 ±1.8F) and 90 ±2 percent relative humidity. Immediately following conditioning, the specimen is placed in the testing apparatus and secured Voltage is to be applied across the thickness of the specimen (between electrodes 1 and 3 of Figure 24.1). The duration of the applied direct voltage is 1 minute at 500 V. The resistance is to be accurately measured.
22.4 The test procedure for surface resistance or conductance is described in paragraph 12.3 of the Standard Test Methods for DC Resistance or Conductance of Insulating Materials, ASTM D 257 (Dielectric and resistive properties of solid insulating materials — Part 3-3: Determination of resistive properties (DC methods) — Insulation resistance. IEC 62631-3-3). Samples are to be conditioned as described in 22.3. After conditioning. the specimen is placed in the testing apparatus and secured Voltage is to be applied across the surface of the specimen, The 500 V dc voltage is to be applied for 1 minute The resistance is to be accurately measured
22.5 From the data obtained, the volume resistivity and surface can be calculated.UL 746A-2020 pdf free download.