Electrical tracking resistance of polymers

This summarizes a 4-year investigation of electrical surface-tracking properties of many types of synthetic polymers, including (1) thermoplastic dielectrics (for technical reference), (2) rigid casting resins and laminates for enclosed outdoor apparatus, (3) rubbery encapsulating compounds for outdoor components, with and without various fillers, mostly inorganic. Tracking under moist conditions was obtained with a salt-dust-and-fog test, and dry tracking was measured with the ASTM low-current arc-resistance test, D495.