Investigating alternative routes for semi-aromatic polyamide salt preparation: The case of tetramethylenediammonium terephthalate (4T salt)

摘要

In the current article, the effect of different techniques was investigated on the preparation of tetramethylenediammonium terephthalate (4T salt), which consists of an industrially important precursor of high-performance polyamides. In particular, 4T salt was synthesized through solution, slurry, and solvent-free techniques. In each case the salt was isolated as a solid, correlating for the first time the salt preparation/isolation method with attained properties and morphology. This correlation led to a generalized comparison between all synthesized 4T salt grades, aiming at understanding the preparation mechanism of 4T salt. Accordingly, highly pure 4T salt, free of any unreacted diacid traces, can be only obtained from a clear salt solution either by cooling or by nonsolvent addition. Furthermore, by altering the crystallization conditions of the salt, thermal and morphological properties can be significantly affected, which further result in a qualitative correlation with the rate of subsequent direct solid-state polymerization (DSSP). The DSSP reactions were carried out in the microscale of a thermogravimetric chamber, where the different 4T salt grades were heated isothermally until full conversion. Polyamide grades of different thermal and analytical properties were received, underlining that the quality of the salt is a corner stone for subsequent DSSP. These findings can be further exploited also to the DSSP of other semi-aromatic polyamides. (c) 2015 Wiley Periodicals, Inc.