In glassy polymers

In glassy polymers tire interactions of tire penetrant molecules witli tire polymer matrix differ from one sorjDtion site to anotlier. A limiting description of tire interaction distribution is known under tire name of tire dual-soriDtion model [, 60]. In tliis model, tire concentration of tire penetrant molecules consists of two parts. One obeys Henry s law and tire otlier a Langmuir isotlienn ... 

Atomistically detailed models account for all atoms. The force field contains additive contributions specified in tenns of bond lengtlis, bond angles, torsional angles and possible crosstenns. It also includes non-bonded contributions as tire sum of van der Waals interactions, often described by Lennard-Jones potentials, and Coulomb interactions. Atomistic simulations are successfully used to predict tire transport properties of small molecules in glassy polymers, to calculate elastic moduli and to study plastic defonnation and local motion in quasi-static simulations [fy7, ( ]. The atomistic models are also useful to interiDret scattering data [fyl] and NMR measurements [70] in tenns of local order. 

Models of chain pull-out in glassy polymers without crazing... 

Schnell, R., Stamm, M. and Creton, C., Direct correlation between interfacial width and adhesion in glassy polymers. Macromolecules, 31, 2284-2292 (1998). 

Kolarik, J. Secondary Relaxations in Glassy Polymers Hydrophilic Polymethacrylates and Polyacrylates Vol. 46, pp. 119—161. 

Water molecules combine the tendency to cluster, craze and plasticize the epoxy matrices with the characteristic of easily diffusion in the polymer1 10). The morphology of the thermoset may be adversaly influenced by the presence of the sorbed moisture. The diffusion of the water in glassy polymers able to link the penetrant molecules is, therefore, characterized by various mechanisms of sorption which may be isolated giving useful information on the polymer fine structure. 

However, the transport of a penetrant in glassy polymers is much more complex. It has been clearly shown 21.23.33> gases and vapours sorb in glassy polymers... 

X 10, and 7.8 X 10 kg/mol-ns respectively. Note that these values are at the level which we identified with the onset of configurational motion inhibition. In glassy polymers, we expect the effective value of 7c to be significantly larger than the roughly 5 x 10 kg/mol-ns calculated above because the actual repulsive part of the van der Waals potential is much steeper than a quadratic fit of Equation 2. Let us emphasize again the approximate... 

HB Hopfenberg, V Stannett. Diffusion and sorption of gases and vapors in glassy polymers. In RN Haward, ed. The Physics of Glassy Polymers. New York Wiley, 1973, pp 504-547. 

T Alfrey, EF Gurnee, WG Lloyd. Diffusion in glassy polymers. J Polym Sci Part C 12 249-261, 1966. 

VS Vadalkar, MG Kulkarni, SS Bhagwat. Anomalous sorption of binary solvents in glassy polymers Interpretation of solute release at constant rates. Polymer 34 4300-4306, 1993. 

HL Frisch. Sorption and transport in glassy polymers. Polym Eng Sci 20 2-12, 1980. 

JC Wu, NA Peppas. Modeling of penetrant diffusion in glassy polymers with an integral sorption Deborah number. J Polym Sci Polym Phys Ed 31 1503-1518,... 

JX Li. Case II sorption in glassy polymers Penetration kinetics. PhD Dissertation, University of Toronto, Toronto, Canada, 1998. 

FA Long, D Richman. Concentration gradients for diffusion of vapors in glassy polymers and their relation to time dependent diffusion phenomena. J Am Chem Soc 82 513-522, 1960. 

THE BERENS-HQPFENBERG MODEL. The Berens and Hopfenberg model considers the sorption process in glassy polymers as a linear superposition of independent contributions of a rapid Fickian diffusion into pre-existing holes or vacancies (adsorption) and a slower relaxation of the polymeric network (swelling).(lS) The total amount of sorption per unit weight of polymer may be expressed as... 

Regarding the effects of shear band structure on the fracture mode in glassy polymers, Wu and Li [170] concluded that when microshear bands propagate in a specimen cross section, a shear failure is produced with a very small overall de-... 

---