Compositional dependence of glass transition temperature

Figure 3. Composition dependence of glass transition temperature of PVPMPS-18/PVPr blends.

Gupta R K. and Mauro J. C., Composition dependence of glass transition temperature and fragility. I. A topological model incorporating temperature-dependent constraints. /. Chem. Phys., 130, 094503/1-094503/8 (2009). 

Schult K. A., and Paul D. R., Techniques for Measurement of Water Vapor Sorption and Permeation in Polymer Films, J. Appl. Polym. Sci, 1996, 61, 1865-1876. Mattera V. D., Jr., and W. M. Risen, Jr., Composition dependence of Glass Transition Temperature of Sulfonated-Polystyrene lonomers, J. Polym. Sci., Part B, Polym. Phys., 1986, 24, 753. 

This leads to a dependence of glass transition temperature on composition... 

Figure 2. Dependence of glass transition temperature, T , on composition for samples cured with schedule A.

Figure 3. Dependence of glass transition temperature on composition of samples cured at ambient temperature and following subsequent heat-up. Key to cure schedule -----------------, A , B and B + heat-up to 180°C.

Table 16.3 Dependence of Glass Transition Temperature and Melting Point on Composition...

In Fig. 46 the dependences of glass transition temperature Tg, determined by the thermomechanical method, on formal contents cform are shown for the indicated copolymers. As one can see, the dependences Tg(cform) course is different for these copolymers. For APESF the values Tg are situated above additive glass transition temperature, for CP-OFD-lO/P-1 — lower and for diblock-copolymers CP-OFD-lO/OSF-10 the dependence Tg(cform) has sigmoid character. Such course of the dependences Tg(cform) for the indicated copolymers supposes different change Kh with copolymers composition. The value KM can be estimated according to tlie well-known Gordon-Talor-Wood equation [143] ... 

Dynamic mechanical analysis is the most widely used technique for the investigation of mechanical properties and the structure-property relationships in polymeric materials. The dynamic mechanical results expressed as storage modulus ( ), loss modulus ( ") and loss tangent (tan S) in the function of temperature demonstrate for example the phase composition, phase transition with glass transition temperature and the structural relaxation processes. The phase segregation in the cured UPRs with an increase in styrene concentration and the dependence of glass transition temperature of UPRs... 

Since the homogeneous nucleation probability cannot be measured for glass-forming liquids, it has not been possible to either prove or disprove this denial of an in-principle ground state for the hquid state of simple substances. The plausibility of Kauzmann s resolution, however, has suffered from the identity of behavior of crystallizable and atactic (noncrystalliz-able) polymers, and by the experimental contrasts in the composition dependencies of homogeneous nucleation temperatures and glass transition temperatures (7 and T ) observed in binary solutions. 

The chromophores serve for the formation of efficient photorefractive gratings and they are photo-chemically active, probably by 2 -n 2 photochemical reactions, when triplet sensitized. The photorefractive external diffraction efficiency is highly dependent on the glass transition temperature of the composites. A low glass transition temperature favors the efficiency. 

At present, the most common way to gain information about the phase behavior of polymer systems is first to obtain experimental data about the temperature and composition dependence of phase transitions and then to interpret them by applying thermodynamic principles. Following this semi-empirical method, the observation of glass transition(s) is commonly used to study miscibility in amorphous and semicrystalline mixtures. 

Since successful commercialization of Kapton by Du Pont Company in the 1960s (10), numerous compositions of polyimide and various new methods of syntheses have been described in the Hterature (1—5). A successful result for each method depends on the nature of the chemical components involved in the system, including monomers, intermediates, solvents, and the polyimide products, as well as on physical conditions during the synthesis. Properties such as monomer reactivity and solubiHty, and the glass-transition temperature,T, crystallinity, T, and melt viscosity of the polyimide products ultimately determine the effectiveness of each process. Accordingly, proper selection of synthetic method is often critical for preparation of polyimides of a given chemical composition. 

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