Hygrothermal behavior of electro-active paper actuator

Abstract

Mechanical properties of the electro-active paper (EAPap) actuator were tested to investigate its hygrothermal behavior. Tensile creep behavior was studied with constant load at 30–70% relative humidity ranges and 25–40°C temperature. Creep deformation showed typical trend of abrupt strain increase in a short period followed by steady increase of strain, which resulted from the breakdown of cellulose microfibrils. Dependence on the material orientation of EAPap was observed in the creep tests. As changing the orientation of EAPap samples, the creep resistances were varied. Creep strains and creep strain rates were increased as increasing the relative humidity level at 25°C. However, at the elevated temperature of 40°C, the creep strain rate at secondary creep was not significantly raised under increased relative humidity level from 30% to 50%. The hygrothermal effect by increasing the relative humidity level and temperature on the creep rate was reduced due to the saturated moisture at a higher temperature even with lower humidity level. The activation energy levels for creep were around 607–658 kJ/mol for 30% relative humidity level and 623–671 kJ/mol for 50% relative humidity level depending on the material orientation. Understanding of hygrothermal effect in conjunction with the humidity and temperature provides useful information for the potential nano-bio applications of the EAPap actuator.