Hygrothermal Effects on Physical Aging and Structural Recovery of an Epoxy Thermoset
W H. Han, G B. McKenna
We have investigated the hygrothermal effects on thin epoxy films (c.a. 60 :m thick) using mass uptake, swelling, and uniaxial creep compliance measurements inside a dew formation-free transparent chamber capable of arbitrary relative humidity and temperature controls. We show that the physical aging behavior in humidity down-jumps is equivalent to temperature down-jumps such that the time-aging time superposition principle holds for both cases. In addition, volume change measurements after up- and down-jumps in RH are the first demonstration of an asymmetry of approach induced by moisture changes in a material. Preliminary efforts to extend the TNM-KAHR models of structural recovery to account for moisture induced aging effects are presented.