Synthesis and Characterization of Low-Melting-Point Polyamides with Trace Thermoreversible Cross-Linked Networks

Abstract

In this study, we synthesized low-melting-point polyamides (LMPAs, T m ≈ 145 °C), which were composed of εcaprolactam, hexamethylenediamine, adipic acid, 1,10-decanedicarboxylic acid, and 2,5-furandicarboxylic acid. The LMPA materials with temperature-triggered reversible cross-linking were prepared by adding various bismaleimide (BMI) loadings (0, 0.1, 0.5, and 1.0 wt %), and their thermal and mechanical properties were obviously better than those of pure LMPA without BMI loading. According to rheological studies, the temperaturetriggered reversible cross-linking (i.e., Diels−Alder reaction) described above occurs at a temperature range of 150−160 °C. In addition, the rheological activation energy of LMPAs with crosslinked networks was significantly higher than that of LMPA without cross-linked networks (298.6 vs 77.7 J kg −1 K −1 , respectively). For mechanical properties, the yield strength of LMPAs with BMI loading (29.1−36.5 MPa) was higher than that of LMPA without BMI loading (19.1 MPa), which was improved by about 50%. As a method of developing LMPA materials with high performance, this is the first report of LMPA materials with temperaturetriggered reversible cross-linking.

Synthesis and characterization of ultra‐tough crosslinked polyamide with hybrid polymer networks equipping strong hydrogen bonds

“…The introduction of more linear amide bonds made their hydrogen-bonding networks and orderliness increase, thereby improving their rigidity and limiting chain mobility. 6 Notably, the G' curve of BH37 and BH55 exhibited two large-scale modulus changes, which attributed to the transition from the glassy state of polymer to the rubbery state of polymer and the crystalline melting of polymers, 18 respectively. A sufficient amount of BAHD in the cPAs system can be made the crystalline ability of cPAs increase.…”