Polyethylene terephthalate, polycondensation

Condensation polymerization differs from addition polymerization in that the polymer is formed by reaction of monomers, each step in the process resulting in the elimination of some easily removed molecule (often water). E.g. the polyester polyethylene terephthalate (Terylene) is formed by the condensation polymerization (polycondensation) of ethylene glycol with terephthalic acid ... 

Challa, G., The formation of polyethylene terephthalate by ester interchange I. The polycondensation equilibrium, Macromol. Chem. Phys., 38, 105-122 (1960). 

Tomita, K., Studies on the formation of polyethylene terephthalate 6. Catalytic activity of metal compounds in polycondensation of bis(hydroxyethyl)terephthalate, Polymer, 17, 221-224 (1976). 

Ravindranath, K. and Mashelkar, R. A., Modeling of polyethylene terephthalate) reactors. IX. Solid state polycondensation process,./. Appl. Polym. Sci., 39, 1325-1345 (1990). 

Stevenson, R. W. and Nettleton, H. R Polycondensation rate of polyethylene terephthalate). I. Polycondensation catalyzed by antimony trioxide in presence of reverse reaction, J. Polym. Sci., Part A-1, 6, p. 889-900 (1968). 

Yokoyama, H., Sano, T., Chijiiwa, T. and Kajiya, R., Polycondensation rate of polyethylene terephthalate at reduced pressure, J. Jpn. Petrol. Inst., 21, 58-62 (1978). 

Castres Saint Martin, H. and Choi, K. Y., Two-phase model for continuous final-stage melt polycondensation of polyethylene terephthalate). 2. Analysis of dynamic behavior, Ind. Eng. Chem. Res., 30, 1712-1718 (1991). 

Devotta, I. and Mashelkar, R. A., Modelling of polyethylene terephthalate reactors - X. A comprehensive model for a solid-state polycondensation process, Chem. Eng. Sci., 48, 1859-1867 (1993). 

Polycondensation reactions were also carried out using a mixture of ethylene-diamine and adipic acid (55). IR techniques again were used to confirm the polymer composition. The results are summarized on Table 9. The chemistry of polyethylene terephthalate) mechanical polycondensation with diamines proceeds as follows ... 

The mechanochemical polycondensation reaction has been studied using heterochain polymer systems—polyethylene terephthalate poly-(e-caprolactam), cellulose, etc.—characterized by end groups that can be activated to increase their own number by mechanochemical destruction of corresponding polymers. The mechanochemical destruction was done in the presence of some suitable condensing agents, such as aliphatic and aromatic diamines and fatty acid dichlorides. 

Figure 7. Mechanochemical polycondensation of polyethylene terephthalate with ethly-lenediamine 1, oxygen atmosphere 2,...

In addition, such a method of synthesis can be generated by making use of another destructive means for ligand synthesis. In that sense, the method was verified by achieving some polycondensation products of polyethylene terephthalate and ethylenediamine and their complexation with different metals by irradiating the system with cobalt-60 (gamma rays). These results also make up the subject of other studies. 

Of some interest are chelation processes occuring along with the synthesis of macromolecular ligands. This can be exemplified by a mechano-chemical activation of polyethylene terephthalate and en polycondensation to give the following complexes [112] ... 

The rotating-disk reactor is applicable for bulk polycondensation reactions such as those for the productions of Nylon 66 and 610, polyethylene terephthalate, polyurea, and polycarbonate. High agitation and multidisks provide a high rate of surface renewal, which increases the efficiency of the reaction process. 

Diethylzinc was used as a catalyst for the preparation of polyesters from terephthalaldehyde via the Tischenko reaction (480), and for the polycondensation of ethylene glycol with dimethyl terephthalates to afford polyethylene terephthalate (340). Benzylzinc chloride has been used as a catalyst for polycondensation of benzyl chloride (223). 

In commercial practice today reactions of the second type frequently utilize an excess of glycol, increasing the rate of esterification. Later stages of such polycondensations, as in the preparation of polyethylene terephthalate, take place by a transesterification mechanism with liberation of glycol. The direct esterification reaction may be catalysed by a second molecule of the carboxylic acid (self-catalysis) or by an independent acidic catalyst (catalysed esterification). 

It is interesting to mention that the first truly synthetic (not based on natural products) polymer material was bakelite obtained in 1907 via polycondensation of phenol and formaldehyde. This material had good dielectric properties and was used mainly as an electrical insulator. The most famous polycondensation polymer is probably nylon belonging to the class of polyamides. Other common classes of polycondensation polymers are polyesters (like polyethylene terephthalate), polysiloxanes, polycarbonates, polysulfides, polyethers and polyimides. 

A special form of condensation polymerization occurs when the monomer can react with itself Conceptually, the monomer has the form AMB. The initial stoichiometry is perfect so there is no inherent limitation on molecular weight. Typically, however, there is an equilibrium limitation caused by the condensation by-product. Self-condensing polymerizations can be regarded as a special case of binary polycondensations, as discussed above, that start with the dimer, AMNB. This view is a bit misleading with respect to the actual chemistry. The final reaction step in the manufacture of polyethylene terephthalate is... 

Polybutylene terephthalate (PBTP, PBT, and polytetramethylene terephthalate) n. A member of the polyalkylene terephthalate family, similar to polyethylene terephthalate in that it is derived from a polycondensate of terephthalic acid, but with butanediol rather than glycol. PBTP can be modified easily to overcome its relatively low-operating-temperature limit, making it equivalent to plastics used in... 

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