Rubbery polymers physical constants

The differences in the transport and solution behavior of gases in rubbery and glassy polymers are due to the fact that, as mentioned previously, the latter are not in a state of true thermodynamic equilibrium (1,3-8). Rubbery polymers have very short relaxation times and respond very rapidly to stresses that tend to change their physical conditions. Thus, a change in a temperature causes an immediate adjustment to a new equilibrium state (e.g., a new volume). A similar adjustment occurs when small penetrant molecules are absorbed by a rubbery polymer at constant temperature and pressure absorption (solution) equilibrium is very rapidly established. Furthermore, there appears to exist a unique mode of penetrant absorption and diffusion in rubbery polymers (2) ... 

The sorption coefficient S was indirectly obtained, by dividing the permeability coefficient P by the diffusion coefficient ). The well-known relationshipP = DS with constant diffusivity D was assumed to be valid (which is generally the case for gas permeation in rubbery polymers at relatively low pressure). The diffusivity D is considered to be affected by the free volume, i.e. the unoccupied space in the polymer matrix, and the solubility S by physical and chemical interactions between gas and polymer. 

It is necessary therefore to consider the deformation of polymers as affected by temperature and rate of loading as well as of the stress imposed. Unlike the elasticity of the rubbery state, for which a reasonable theoretical treatment exists dependent on fundamental physical constants and molecular concepts, the glassy state can only be treated by a phenomenological approach. 

V/2 PHYSICAL CONSTANTS OF RUBBERY POLYMERS TABLE 1. cant d... 

The phenomenon of polymer swelling, owing to sorption of small molecules, was known even before Staudinger reported [1] in 1935 that crosslinked poly(styrene) swells enormously in certain liquids to form two-component polymer gels. The physical state of such systems varies with the concentration (C) and molecular structure of the sorbed molecules thus, the system undergoes transition at constant temperature from a rigid state (glassy or partially crystalline) at C < Cg to a rubbery state at Cg (the transition state composition). When C > Cg and the second component is a liquid, its subsequent sorption proceeds quickly to gel-saturation and of course a solution is produced if the polymer lacks covalently bonded crosslinks or equivalent restraints. Each successive physical state exhibits its own characteristic sorption isotherm and sorption kinetics. 

---