Solid state polymerization in a micro‐reactor: The case of poly(tetramethylene terephthalamide)

Abstract

The aim of this work was to develop and optimize a direct solid state polymerization (DSSP) process on a micro scale for alkyldiammonium-terephthalate salts. This was successfully demonstrated for the first time by the case of tetramethylenediammonium-terepththalate salt (4T salt). The derived polymer (PA4T) presents interesting properties, but the temperature-favored acid catalyzed cyclization of tetramethylenediamine (TMD) to mono-functional pyrrolidine and ammonia inhibits a high polymerization conversion. DSSP was performed in a thermogravimetrical analysis (TGA) chamber, and the continuously monitored weight loss was correlated to polymerization conversion via the release of water, excluding any mass and heat transfer limitations. It was found that the conditions under which the DSSP is performed and the morphology of the starting material affect both the reaction rate and the product quality. The effect of the critical process parameters, namely vent size, heating rate to reach SSP temperature, and reaction temperature were quantified by the observed mass loss and by 1 H NMR analysis. It was noticed that, besides the water formed by amidation, other volatile compounds were also released during the DSSP reaction, with main component, the TMD. In particular, it was observed that conditions favoring the evaporation of TMD also favored a higher reaction rate. The TMD loss was minimized by optimization of the aforementioned process conditions, leading to a more thermally stable and a higher molecular weight final product. The thermal stability of the PA4T was found to be inversely correlated to the concentration of carboxylic end groups present in the formed polymer.

Thermal properties of α,ա- aminoalkylterephthalamides prepared from waste poly(ethyleneterephthalate) bottle and aliphatic diamines

“…The principal peak at 450 °C was due to polyamide decomposition. This decomposition temperature was lower than the reported value of 460 C of PA4T prepared from salts [6].…”

“…A series of semiaromatic polyamide salts were prepared in solution by neutralizing aliphatic diamines of different aliphatic length with terephthalic acid. The obtained semiaromatic salts were further subjected to direct solid state polycondensation that performed in a TGA chamber [5,6].…”

New Aspects on the Direct Solid State Polycondensation (DSSP) of Aliphatic Nylon Salts: The Case of Hexamethylene Diammonium Dodecanoate

“…The nucleation stage occurs first on the surface of the crystallites and then in the defective sites. In parallel it has been confirmed that during the initial stages of the DSSP of polyamide salts, the volatile diamine component escapes in both aliphatic (nylon ® ) salts and semi-aromatic polyamide salts [ 20 , 28 , 29 , 32 , 33 ]. In addition, in a DSSP study on PA 66, it was discovered that diamine loss preceded water formation, thus resulting in even more defects in the salt crystal lattice, which in turn are active centers for initiation and propagation [ 20 ].…”

“…The direct solid state polymerization (DSSP) of polyamide salts has been systematically investigated in our laboratory since the late 1970s [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. DSSP involves heating the solid reacting mass at a temperature below its melting point and the melting point of the final polymer product under an inert atmosphere as to allow the progression of the polycondensation, while maintaining the solid phase in the reacting mass.…”

High-Solids, Solvent-Free Modification of Engineered Polysaccharides

“…Then, laboratory scale runs in different assemblies were performed so as to confirm the findings from the micro scale. This approach is modeled after the fundamentals of the solid state polycondensation (SSP) of polyamide salts, and lessons from this research field have been adapted in this work [ 27 , 28 , 29 , 30 ]. Thus, a TGA aluminum crucible was used as a micro-scale reactor.…”