Hydration in a new semiaromatic polyamide observed by humidity‐controlled dynamic viscoelastometry and X‐ray diffraction

Abstract

Hydration in a new semiaromatic polyamide, named polyamide 9-T (PA9-T), a copolymer of terephthalic acid with n-and iso-nonanediamine, is studied by dynamic viscoelastic analysis under controlled humidity conditions and wide-angle x-ray diffraction analysis in comparison with common polyamide nylon 6. The storage modulus of PA9-T is retained at up to 60 ºC with increasing humidity, then dropping with further increases in temperature past 70 ºC. The decrease in mechanical properties at 70 ºC due to moisture uptake is found to be substantially improved by annealing to develop molecular packing and/or crystallization. In contrast, the storage modulus of very highly crystallized (50% crystallinity) nylon 6 decreases markedly with humidity at low temperatures such as 20 ºC. Thus, PA9-T retains its mechanical properties in humid atmospheres at much higher temperatures than nylon 6. The crystalline x-ray diffraction peaks for nylon 6 corresponding to (002) + (202) of α form shift upon absorption of moisture, speculated to be due to the weakening of hydrogen bonds and the subsequent conformational disordering of the chains. Unlike nylon 6, the crystalline peaks of PA9-T do not shift due to moisture uptake. This is considered to be attributable to that the long aliphatic chain in PA9-T forms the large hydrophobic domain, rendering PA9-T less hygroscopic than nylon 6. Additionally, strong hydrogen bonds formed by terephthalamide residues together with a strong stacking force of phenylene groups may also repel water, preventing moisture bind with the amide groups of PA9-T crystals.

Effects of Take-up Speed of Melt Spinning on the Structure and Mechanical Propertiesof Maximally Laser Drawn PA9-T Fibers

“…More elaborately, PA9-T possesses a high heat deflection temperature and can retain mechanical properties at elevated temperature. Moreover, it exhibits excellent mechanical properties and dimensional stability under high humidity [16]. It assumes proper melt viscosity for injection/extrusion molding.…”

Semiaromatic polyamide poly(hexamethylene terephthalamide)‐co‐polycaprolactam: Thermal and flame‐retardant properties

“…Accordingly, semiaromatic polyamide is considered to be a high‐performance material because of its high‐temperature dimensional stability, corrosion‐resistance properties, and low moisture uptake. However, only a few semiaromatic polyamides, such as poly(nonamethylene terephthalamide), poly(decamethylene terephthalamide), and copolymer poly(hexamethylene terephthalamide)‐ co ‐poly(hexamethylene hexanediamide) (PA6T/66) and poly(hexamethylene terephthalamide)‐ co ‐polycaprolactam (PA6T/6) copolymers, are commercial and processable because it is difficult to account for their thermal performance and processability simultaneously. In our previous study, we introduced aliphatic linkages or thioether units into the semiaromatic polyamide main chain as flexible segments to improve its processability .…”

Investigation of the synthesis and properties of isophorone and ether units based semi-aromatic polyamides

“…In order to improve the thermal properties of aliphatic polyamides, the incorporation of aromatic units into the polymer main chain acts as an efficient approach. 10 However, only a few semi-aromatic polyamides, such as the copolymer of PA6T, 11 poly(nonamethylene terephthalamide) (PA9T), [12][13][14][15] poly(decamethylene terephthalamide) (PA10T), the product of Dupont, Solvay, Mitsui, Evonik and so on, are commercially available. 8) and Aramid-1313 (ref.…”