Soil Burial Tests: Effect of Soil Burial Exposure on the Properties of Electrical Grade Reinforced Plastic Laminates

Twenty-three types of unclad laminates based on phenolic, melamine, silicone, epoxy, and polyester resins were examined after exposure in alkaline soil at Roswell, New Mexico, and in acid soil at Bainbridge, Georgia. 1-3 The laminate thickness was 1/16 inch nominal in all cases. Tests were made of insulation resistance, flexural strength, and flexural modulus. The properties evaluated included: (?') Insulation resistance after conditioning four days at 90 percent relative humidity and 95°F, using a tapered pin method in accordance with ASTM D257. Five replicates for each below-ground exposure condition were tested, each of which provided three readings to give fifteen readings for averaging. Two replicates were measured for each of the shelf-aging specimens, to give six readings for averaging. (ii) Flexural strength and modulus of elasticity in flexure in accordance with ASTM D790. Five replicates for each exposure condition were tested. 47 48 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY