EFFECT OF RELATIVE HUMIDITY CHANGES ON COMPRESSIVE CREEP RESPONSE OF PAPER

The compressive creep response of corrugated fiberboard specimens under edgewise loading was determined in both cycle (90-35%) and constant (90%) relative humidity (RH) environments at 51, 57, and 65% of maximum stress (based on the compressive strength at 90% RH). Creep rates were much greater and survival times considerably less for specimens in a cyclic RH environment than for similarly loaded specimens in a constant RH environment. The difference in creep response between cyclic and constant RH became greater as the stress level was increased. The resulting creep strains for cyclically conditioned specimens were higher than those reported for edgewise compressive strain of paperboard. It is concluded from this study that paperboard products under edgewise compressive loading and cycled between 90 and 35% RH will fail sooner than in a constant (90%) RH environment even though the average moisture content may be lower under cyclic RH conditions.