Effects of Fluids Fundamental Aspects

When polymers are exposed to ambient fluids or vapor, the highly mobile and generally small molecules of the ambient phase penetrate the polymer by means of what may be conceived as a random walk process. This process proceeds until the attainment of equilibrium. Equilibrium may be formally attributed to a balance in internal and ambient chemical potentials in the absence of flux. Alternately, it is possible to associate equilibrium with the state where fluid molecules became 

Application and removal of a step strain at times t = 0 and t = to, respectively 

Regarding sea water, this fiuid consists of about 3.5% of chemical elements, of which 30% are sodium and 55% chloride. Most of these elements are nearly entirely 

The ingress of water is associated with increased separation between the molecular chains, thereby inducing expansional strains. This phenomenon, called plasticization, enhances chain mobility in a manner akin to that of rising temperature. It was therefore possible to associate the creep and relaxations of wet polymers with concentration dependent a hygral shift factor an(m) analogous to a-iff). Typically, the plasticization process is thermodynamically reversible. 

It is worth noting that fluids suppress the level of the dry Tg. This reduction is commonly related by (McKague et al. 1978) 

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