Poly condensation process

PCT, PETG, PCTG and PCTAs can all be prepared readily via standard melt-phase poly condensation processes [34, 35], The diacid can be delivered via transesterification of the dimethyl esters or via direct esterification of the diacids. Numerous conventional catalyst and catalyst combinations can be employed. The use of a catalyst or catalyst combination is important for the manufacture of polyesters via the melt-phase process and has been well reported in the literature [36-41], Appropriate catalyst systems enable the production of polyesters with high processing rates and high molecular... 

T. J. Suen, A. M. Schiller, and W. N. Russell, in Polymerisation and Poly condensation Processes (Adv. Chem. Ser. 34), American Chemical Society,... 

Zhang, H., B. Klumperman, W. Ming, H. Fischer, and R. van der Linde, Macromolecules, 34, 6169 (2001). Zutty, N. L. and R. D. Burkhart, Polymer Synthesis at High Pressures, Chap. 3 in Polymerization and Poly condensation Processes, N. A. J. Platzker, ed., American Chemical Society, Van Nostrand Reinhold, New York, 1962. 

N.G. Annenkova, A.B. Blumenfeld, L.A. Vavilova, N.K. Pinaeva, M.E. Savina and A.G. Chernova in International Subject Collection Poly condensational Processes and Polymers, 1985, Nal chik, Russia, p.16-24. (In Russian)... 

Devalues, obtained for PAr and PUAr poly condensation process, showed, that the indicated processes were realized by aggre tion cluster-cluster mechanism [49], i.e., by small macromolecular coils joining in larger ones [23], Thus, polycondensation process is a fractal object with dimension D. reaction. Such reaction can be presented schematically in a form of devil s staircase [80], Its horizontal parts correspond to temporal intervals, in which reaction is not realized. In this case polycondensation process is described with irsing fractal time t, which belongs to Kantor s set points [81], If polycondensation process is considered in Euclidean space, then time belongs to a real number set. 

Let us consider the physical sense and definition of fractional exponent Vg. value in the given context. As it is known [84, 85], polycondensation process ceases in gelation point, for which the fractal dimension dj of a forming stmcture is equal to 2.50. This means, that fractal (macromolecular coil) fraction, not included in evolution (poly condensation) process, at gelation point reaches its maximum value V =1.0. From the said above it follows, that in the considered case at v =1.0 d=D =... 

The fractal Eq. (27), where Dj. value is determined according to the Eq. (17), can be used for interfacial poly condensation process quantitative description. Calculated according to the Eq. (17) D. values ate adduced in the Table 6, from which large enough interval of their variation follows Dj.=1.592-2.055. 

As in the Eq. (64) X value has no effect on the distribution P (N), then the indicated relationship supposes three basic parameters influencing on distribution P (N) d, b and ty. Each of the indicated parameters characterizes a certain feature of the poly condensation process. The exponent d is thus essentially defined by the macromolecular coil stmcture, that directly follows from the Eq. (63). The value b characterizes the type and intensity of the destructive processes. Parameter is determined by the stochastic contribution to a polycondensation process and it is possible to assume dependence on comonomers initial concentration c the greater C(, the higher the probability of random collisions. This postulate is particularly important for the mode of interfacial polycondensation, where synthesis proceeds not in all reactive vessel volume, but only in the interfacial layer, for which enhanced in comparison with average value the magnitude c is expected. All experimental MWD curves have the unimodal shape that supposes low mobility for coils in solution or < 2/3 [101]. 

Let us note in conclusion, that the indicated above and considered factors, the chain destruction appreciation [101], catalyst influence [48] and so on can be required. Nevertheless, the adduced above results demonstrated clearly both possibility and expediency of the considered approach for polymerization processes in general and polycondensation in particular. The conclusion about poly condensation process fractal character should be recognized as particulariy important, since it cannot be reaUzed for compact coils (globules) with 0 = d = 3 [ 113]. 

Thus, the stated above results allow to make at aity rate two conclusions. The first from them concerns qnantitative description complexity of such processes as polycondensatioa Actually such obvious enough effect as Q and (or MM) change at reagents relation variation reqnires nsaging, as a minimum, of three independent parameters, moreover two from them (q and D ) are difficnlt enough to predict. The second conclnsion consists of the fact that even the simplest used above model of the considered effect quantitative description has shown its effectiveness and, hence, perspectiveness for poly condensation processes prediction as a whole, including a computer one. 

Mikitaev, A. K. Musaev, Yu. L Korshak, V. V. Kinetics and mechanics of high-tem-perature polycondensation reaction in solution at polyarylates synthesis. In collection Poly condensation processes and polymers. Ed. Mikitaev, A. Nal chik, KBSU, 1976,180-211. 

Russian and foreign scientists remarkably succeeded in both areas of creation of new inflammable, heat- and thermal resistant polycondensation polymers and areas of development of methods of performing polycondensation and studying of the mechanism of reactions grounding the poly condensation processes [1-6],... 

Polymer plasticization and overcoming compatibility problems helps in synthesis of many polymers in the presence of supercritical carbon dioxide. Carbon dioxide has been fotmd to be inert towards free radicals and cations but dramatically decreases glass transition temperamre of polymer due to plasticization (e.g., polystyrene Tg is reduced by about 50°C). Plasticization is especially useful in melt phase poly condensation processes. 

Polymerization and Poly condensation Processes (Platzer, N. A. J., ed.), American Chemical Society, Van Nostrand Reinhold, New York, Chapter 13. 

Poly condensation Processes and Polymers, Ed., V.V. Korshak, KBSU, Nal chik, Russia, 1985, p.l60. 

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