Nylon 6,6 resins, in the form of pellets, were solid state polymerized in the temperature range of 160 -200°C in a fixed-bed reactor under flowing nitrogen for times of 0 -4 h. The kinetics of the solid state polymerization (SSP) of nylon 6,6 were examined by the evaluation of pertinent rate expressions and the selection of the most suitable one for describing the apparent overall process. The Flory-theory-based kinetic models were the most effective both for this study's data and for data previously published on SSP of different polyamides. Accordingly, SSP rate constants and activation energies were derived, and process parameters, such as the temperature and time, were investigated.

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Polyamides are high polymers that contain the amide repeat linkage in the polymer backbone. Some common terms used with polyamides are nylon, aramid, and polyphthalamide. Nylon is defined as any polyamide having less than 85% of the amide group directly connected to two aromatic groups. Aramid is a polyamide having 85% or more of the amide groups directly connected to two aromatic groups. Polyphthalamide is a polyamide in which the residues of terephthalic acid or a combination comprise at least 55 mol% of the dicarboxylic acid portion of two repeating units in the polymer chain. This article is a general overview of polyamides, with emphasis on technology developed since 1980. There is an extensive coverage of properties including chemical reactions. Manufacturing for most of the important polyamides is discussed. Commercial polyamides incorporate three classes of additives: endcappers; branching agents; and chain couplers. Because of economic advantages and governmental regulations, there has been a substantial increase in recycling of the starting materials for polyamides and energy, most often as steam.

We report observation of an enal product of the decomposition of both nylon-6,6 and a nylon-6,6 model compound, N,N-hexamethylenebis(hexamide), upon 266 nm pulsed UV laser irradiation of these amides. The product is identified by UV resonance Raman spectroscopy, which shows characteristic band frequencies and intensities of the CdC and CdO stretches of the enal. The vibrational assignment and product identification are supported by experiments with 15 N-labeled nylon-6,6. Degradation and spectroscopic characterization under 16 O2, 18 O2, and N2 show that the degradation channel leading to the enal requires molecular oxygen and thereby indicate an oxidative mechanism. The product resonance Raman intensities are directly proportional to the number of photons incident on the sample, consistent with a direct photooxidative process, rather than a thermal-oxidative one with the laser serving as a heat source. We do not observe the enal product when the nylon-6,6 or model compound are simply heated in oxygen-containing atmospheres, except when the heating produces melting.