Antiplasticization, glassy polymers

Carbon-13 rotating-frame relaxation rate measurements are used to elucidate the mechanism of gas transport in glassy polymers. The nmr relaxation measurements show that antiplasticization-plasticization of a glassy polymer by a low molecular weight additive effects the cooperative main-chain motions of the polymer. The correlation of the diffusion coefficients of gases with the main-chain motions in the polymer-additive blends shows that the diffusion of gases in polymers is controlled by the cooperative motions, thus providing experimental verification of the molecular theory of diffusion. Carbon-13 nmr relaxation... 

Studies on the mechanical properties of glassy polymer-solvent or, more generally, polymer-diluent mixtures have been primarily concerned with the deformation behavior at small strains which is governed by the viscoelastic properties of the material. From these studies it is well known that diluents significantly affect relaxation processes in glassy polymers, as clearly evidenced by phenomena such as plasticization and antiplasticization... 

Such behavior is not consistent with plasticization, since the slightly sorbing Hj would not he expected to piestidze the polymer while the more condensable (and hence more strongly sorbing) CO or CH. acts as an antiplasticizer. As is discussed in the section on glassy polymers, such behavior as described here is not anomalous and can be shown to be consistent with inherent properties of glassy polymers under certain conditions. 

Transport Properties. Sorption and transport properties are highly dependent on the post-vitrification history of glassy polymers (77) hence one would expect parameters such as physical aging, antiplasticization and amorphous orientation to affect transport properties. The reduction in diffusivity and permeability due to aging, orientation, and antiplasticization can be modeled via entropy or fi ee volume arguments (77). In addition, diffusive jumps of penetrant molecules in glassy polymers can be affected by (facilitated by) the segmental mobility that is manifested in sub-Tg relaxations 78),... 

However, the rubbery phase should be immiscible with the matrix polymer. Rubbers miscible with glassy polymers function as macromolecular plasticizers for these polymers, showing a decrease in Tg value, toughness, elasticity modulus, and so on. When miscible rubbers are used in small quantity, they produce antiplasticization (see Section 1.5). Polyurethane elastomers are typical examples of those miscible rubbers [40]. 

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