Glassy polymer blends

Gas solubility in glassy polymer blends and mixed gas solubility in glassy polymers. It is worthwhile to consider now some examples of more complex systems, as polymer blends and mixed gases, which are frequently encountered in gas separation with polymeric membranes or in barrier polymer applications. We first consider the solubility of a single gas in glassy polymer blends and then we turn to a case of mixed gas sorption, observing that reliable sorption data for such complex situations, in particular mixed gas sorption data in polymers, are rather rare in the open literature. 

In Figure 2.7, we report the case of two glassy polymer blends the solubility of CH4 in PS-TMPC (tetramethyl polycarbonate) blends of different compositions (0-20-40-60-100% of PS) is shown in Figure 2.7a at 35° while the solubility isotherms of COj in five different blends of (bisphenol-chloral) polycarbonate (BCPC) and PMMA (0-25-50-75% of PMMA)[" 1 at 35° C are shown in Figure 2.7b. The NELF estimation of the solubility is also reported, based only on the pure component characteristic parameters... 

CON Corrforti, R.M., Barbari, T.A., and Pozo de Ferrrandes, M.E., Enthalpy of mixing for a glassy polymer blend fi om CO2 sorption and dilation measurements, Macromolecules, 29, 6629, 1996. 

Mina, M. R, Hague, M. E., Balta CaUeja, P. J., Asano, T., and Alam, M. M. 2004. Microhardness studies of the interphase boundary in rubber-softened glassy polymer blends prepared with/without compatibilizer. Journal of Macromolecular Science B Physics 43(5) 1005-1014. 

At the University of Wisconsin since 19 6, studies of viscoelasticity have evolved from concentrated polymer solutions to undiluted amorphous polymers, dilute solutions, lightly cross-linked rubbers, glassy polymers, blends of different molecular weights, copolymers, cross-linked rubbers with controlled network structures, and so forth. It became evident that each type of system required a different approach. Moreover, in amorphous polymers, the terminal, plateau, and transition zones had to be described separately. Both dynamic (sinusoidal) and transient measurements such as creep and stress relaxation have been utilized. The inderlying theme of this work is the relation of macromolecTilar dynamics—modes of motion of polymer molecules— to mechanical and other physical properties. 

The mechanical properties of homogeneous glassy polymer blends have been reviewed by Kambour. To a first approximation the properties are additive. In many cases negative deviations in ductility are found which are believed to be due to the reductions in mobility associated with the volume contraction on mixing and interactions in the blends. Since these are necessary for mixing to take place, positive deviations are seen as unlikely. Toughened plastics are generally two phase materials. 

The Metravib Micromecanalyser is an inverted torsional pendulum, but unlike the torsional pendulums described eadier, it can be operated as a forced-vibration instmment. It is fully computerized and automatically determines G, and tan 5 as a function of temperature at low frequencies (10 1 Hz). Stress relaxation and creep measurements are also possible. The temperature range is —170 to 400°C. The Micromecanalyser probably has been used more for the characterization of glasses and metals than for polymers, but has proved useful for determining glassy-state relaxations and microstmctures of polymer blends (285) and latex films (286). 

Whilst the volume production of completely new polymers which have achieved commercial viability in recent years has been small, the development of polymer blends has been highly significant. Of these the most important involve a glassy... 

The process of blending with another glassy polymer to raise the heat distortion temperature is not restricted to polycarbonate, and the polysulphones are obvious candidates because of their higher Tg. One blend has been offered (Arylon T by USS Chemicals) which has a higher softening point than the ABS-polycarbonates. 

Note In polymers, because of the low mobility of polymer chains, particularly in a glassy state, metastable mixtures may exist for indefinite periods of time without phase separation. This has frequently led to confusion when metastable miscible polymer blends are erroneously claimed to be miscible. 

Melt-processable polymer blend or copolymer in which a continuous elastomeric phase domain is reinforced by dispersed hard (glassy or crystalline) phase domains that act as junction points over a limited range of temperature, or... 

The applications of polymers as solids are usually related to their mechanical properties. These properties often define them as rubbery, glassy or elastomeric materials. Similar to polymer blends, the final properties of polyrotaxanes will de-... 

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... 

Although most efforts have been devoted to the use of carbon nanotubes in glassy polymers, some studies have reported strong reinforcing effects of CNTs in elastomeric matrices such as butyl (23), natural (17,24-27) and styrene-butadiene rubbers (28-31) as well as styrene-butadiene and butadiene rubber blends (32). 

We have reviewed the recent development of a nonequilibrium statistical mechanical theory of polymeric glasses, and have provided a unified account of the structural relaxation, physical aging, and deformation kinetics of glassy polymers, compatible blends, and particulate composites. The specific conclusions are as follows ... 

Thermodynamically stable mixtures will of course form stable blends. This implies miscibility on a molecular level. It is desirable for some applications but not for others, like rubber modification of glassy polymers. 

Breakdown of the stress-optic rule can also occur in multiphase or multicomponent mixtures, as well as in melts with crystalline domains. However, as in glassy polymers, for miscible blends, a revised stress-optic law can sometimes be recovered by breaking the stress and birefringence tensors into two components, one for each component in the blend (Zawada et al. 1994 Kannan and Komfield 1994). 

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