Has any body done any research to investigate the influence of moisture content on creep behaviours of polymers? like how retardation time changes with moisture content? i have done two materials creep tests and fit a burgers model to data. One material shows that retardation time increases with increasing moisture content, while the other one shows retardation time decreases with increasing moisture content. before i repeat my tests, can any body be kind enough to give me some theoretical guidance on this topic?