Nylon 66 polyamidation kinetics

Most addition polymers are formed from polymerizations exhibiting chain-growth kinetics. This includes the typical polymerizations, via free radical or some ionic mode, of the vast majority of vinyl monomers such as vinyl chloride, ethylene, styrene, propylene, methyl methacrylate, and vinyl acetate. By comparison, most condensation polymers are formed from systems exhibiting stepwise kinetics. Industrially this includes the formation of polyesters and polyamides (nylons). Thus, there exists a large overlap between the terms stepwise kinetics and condensation polymers, and chainwise kinetics and addition (or vinyl) polymers. A comparison of the two types of systems is given in Table 4.1. 

Molecular-Weight Distribution of Condensation Polymers Kinetics and Mechanism of Nylon 66 Polyamidation Amidation... 

Table 7.5 Kinetic scheme to account for polyamidation and thermal degradation in melt-phase nylon 6,6. Reactions 7.5.1-7.5.5 are the kinetic scheme of Steppan et a . [13]. Reactions 7.5.6-7.5.5b were added by Schaffer [41]...

Degradation behaviour of polyamides continues to be the subject of many papers. The degradation of nylon-6 has been examined by hydrolysis,by photolysis, and ultrasonically. Kinetic studies on chain scission by means of e.s.r. spectroscopy showed that the concentration of free radicals originating from broken chains in nylon-6 fibres could be described by a model system in which crystalline and amorphous layers were sandwiched in the fibre direction. Oxyluminescence has also been used in a study of the kinetics of the thermo-oxidative degradation of nylon-6,6. 

A kinetic study on the hydrolysis, acetylation, and deamination of polyamides in 3-cresol solution has been described. First-order rate coefficients and apparent energies of activations of these reactions indicate two distinct reaction regions, an initial fast region followed by a slow one. A two-phase microfibrillar structure for the polymer in solution is proposed to explain these observations. Preswollen nylon-6 fibres can be crosslinked with bifunctional acetoxy- and ethoxy-organo-silanes in anhydrous conditions. The SiOAc and SiOEt functions react with terminal amino and carboxyl groups on the polyamide, and also at a number of amide links. ... 

Recent progress in kinetic and reactor modeling make it possible to assist the reactor design and process operations with unprecedented exactness. A recent analysis of the nylon-6,6 process [138] looked for improvements based on expansion of the solid-state polymerization, but the gain was minor compared to what happened with PET. The reason is the much reduced sensitivity of polyamides to by-product removal as compared to polyesters, since the equilibrium constant of the former is much greater. 

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