CAPROLACTAM POLYMER

As long as all transacylation equilibria can be attained, the molecular weight distribution approaches the most probable one. The existence of a statistical distribution for equilibrium caprolactam polymers has been well established [3, 22—24], and this is an indirect proof of the independence of the reactivity of functional groups on the chain length. 

Fig. 7. Calculated [81] and estimated [16] content of cyclic oligomers in caprolactam polymers.

When calculating the equilibrium concentration of macrocyclics in caprolactam polymers, the heat of polymerization was assumed to be zero [81]. For the aforementioned reasons, the actual polymerizability is certainly higher and, therefore, the estimated content of the individual cyclic oligomers is lower than the calculated one (Fig. 7). 

It has been established, that on the average one to two branches per molecule are present in anionic caprolactam polymers [134, 152]. 

Whereas structure (113) prevails in cationic caprolactam polymers prepared at low temperature and short reaction periods, the fraction of amidine groups increases with temperature and time of polymerization. However, only small fractions of carboxyl groups were found in cationic polymers [180]. Only fractionated polymers contained equivalent amounts of basic and carboxylic groups which could also arise from hydrolysis of acyllactam groups [213]. 

Generally it has been assumed that, in the water initiated polymerization, the concentrations of carboxyl and amine groups are equal. This assumption is not valid at high temperatures (above 265°C for caprolactam polymers) when degradation reactions change the concentration of... 

VER Verezhnikov, V.N., Plaksitskaya, T.V., and Poyarkova, T.N., pH-Thermosensitive behavior of 7V,7V-dimethylaminoethyl methacrylate (co)polymers with A-vinyl-caprolactam, Polym. Sci., Ser. A, 48, 870, 2006. 

O. Kamigaito, Synthesis of nylon 6-clay hybrid by montmorillonite intercalated with e-caprolactam,/. Polym. Sci. Pdym. Chem. 1993, 31, 983-986 (c) Y. Kojima,... 

BraunM.,LevyA.B.andSifniadesS.(1999), Recycling Nylon 6 Carpetto Caprolactam , Polymer-Plastics Technology Engineering, Vol 38, No. 3,471-484. 

The mixed polyamide (anid G-669) is converted to a three-dimensional product at this same temperature. Such a behavior of polycaproamide is apparently explained by the fact that at high temperatures destruction of the caprolactam polymer predominates over thermal and thermooxidative structuring (at comparatively low temperatures - below 200°C —capron is structured at an even greater rate than anid G-669). 

Figure 1. Potentiometric titration of cationic caprolactam polymers (initiator CL HCl). 1 — Titration with base, 2 — back titration with acid, E — concentrations of acidic and basic groups, = strong adds, Ech-Hci caprolactam HCl, E A ocyl-amidinium groups, EjfHj — ammonium groups, Ecooh — carboxylic groups, Ecoow — carboxylic groups formed by alkaline hydrolysis of acyUactams.

Braun M, Levy A B, Sifniades S (1999) Recycling nylon 6 carpet to caprolactam, Polym-Plast Technol 38 471-484. 

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