Kinetics of polyesterification

Chen, S. and Chen, F Kinetics of polyesterification III Solid-state polymerization of poly(ethylene terephthalate),. /. Polym. Sci., Polym. Chem. Ed., 25, 533-549 (1987). 

Statistical kinetics of polyesterification of adipic acid with pentaery thritol and trimethylolethane. J. Chem. Soc. 1967, 1. 

Flory has examined the kinetics of polyesterifications and found that the reactivity of the functional groups is essentially the same as the reactivity of functional groups in monofunctional esterifications. The velocity constant is independent of the molecular size up to a molecular weight of at least 10,000. Since there are molecules with a functionality greater than 2 present in alkyds, they are subject to gelation. The transformation from a viscous material to a gel is sudden. The formation of a small fraction of an infinite-network poljuner is the cause of this gelation. As the reaction continues, more of the gel phase is formed and the resin becomes more tough and less extensible. 

Vaidya, U. R. Nadkami, V. M. Polyester polyols from glycolyzed PET waste effect of glycol type on kinetics of polyesterification. J. Appl Polymer Sci. 1989, 38(6), 1179-1190. 

The properties of PBT based copolymers depend on the composition of the reaction mixture. The composition is influenced by the reaction mechanism and kinetics, which are further influenced by the choice, purity, and the concentration of the main reaction components, by the presence and proper choice of the amount of catalyst and by the reaction temperature. The mechanism and kinetics of polyesterification, polyamidation, polyurethanes and many more have been investigated in the past as well as today . 

Flory, R, Kinetics of polyesterification A study of the effects of molecular weight and viscosity on reaction rate,/. Am. Chem. Soc., 61,3334-3340,1939. 

Another factor which can tend to reduce the yield of long polymer molecules, even when equal numbers of functional groups are employed, is the equilibrium which occurs between the reactants and products during condensation reactions. If the concentration of the condensate (such as water) is allowed to build up the reaction may stop and can even be forced in the reverse direction. This problem is usually readily overcome by removing the condensate and so driving the reaction in the forward direction. Also the kinetics of polyesterification can be rather slow at ambient temperature and so the reactants are often heated to a higher temperature and a catalyst is sometimes added. Both of these two modifications can speed up the reaction. 

Main techniques used in kinetic studies of polyesterifications, Chap. 2. 

Main Techniques Used in Kinetic Studies of Polyesterifications... 

Determination of low molecular weight compounds. The kinetics of monoesterifications or of the first steps of polyesterification can be followed by chromatographic methods. The concentration of each of the species present in the medium can be determined, at least for low molecular weight compounds. 

Since high temperatures and a nitrogen atmosphere are necessary to obtain measurable rates of polyesterification and to remove the reaction water, a loss of volatile reactants can hardly be avoided, especially in early stages of polyesterification. In the last stages, the decrease of the concentration of the volatile reactants can be of the same order of magnitude as their concentration. Consequently, the ultimate points of the kinetic plot have possibly no significance. 

The following critical study is mainly devoted to polyesterifications. However, several kinetic analyses relate to monoesterifications whose results are particularly useful for the understanding of polyesterification kinetics and mechanisms. In fact, there is a large number of articles concerned with esterifications and polyesterifications. 

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