Vitrification concentration

Elbs et al. introduced the concept of the vitrification concentration, the concentration of polymer in a solvent-polymer blend above which a polymer is glassy and mobility is no longer possible. " Kim and Libera showed that PS-b-PB-b-PS (PS cylinders form by thermal annealing) forms parallel hexagonal cylinders when cast from solution and allowed to evaporate slowly. " Compression in the direction of film thinkness indicates that the film further shrinks after the polymer film reaches the vitrification concentration. 

The combination of this knowledge and the results of quick-freezing processes provide a theoretical opportunity to freeze products into a solid, amorphous state. If the freezing velocity is smaller than required for vitrification, but large enough to avoid an equilibrium state, an amorphous mixture will result of hexagonal ice, concentrated solids and UFW. 

A typical pH-dependent leaching plot for Pb is shown in Fig. 11 for vitrification dusts. The plots show the measured concentration of Pb in the pH-dependent leaching test leachate as a function of pH for both the untreated sample and... 

The vitrification of liquids and polymers can be effected not only by the decrease of temperature but also by the increase of pressure [4]. Shishkin and Novak [5] obser ved the dependence of free hydroxyl concentration upon pressure. This effect can be described by Eq. (6) or (8) in the same way as the course of vitrification upon decreasing temperature. 

The glass transition temperature Tg is one of the most important structural and technical characteristics of amorphous solids. The correlations of Tg of linear polymers with their chemical composition, molecular weight, rigidity and symmetry of chains, as well as some other characteristics of macromolecules are well documented 57,58) Thg information on networks is much poorer. At present, for networks there exists mainly one parameter in structure-Tg correlations. It is the concentration of crosslinks — a parameter which is very insufficient, since in networks there are chemical crosslinks of different functionality (connectivity) which are distinguished by their molecular mobility. This means that the topological aspect of the network structure should be taken into account in the Tg analysis. Another difficulty connected with Tg determination of polymers lies in vitrification occurring during polymer formation (Sect. 6). 

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