Synthesis and characterization of poly(hexamethylene terephthalate/hexamethylene oxamide) alternating copolyamide (alt‐PA6T/62)

Abstract

As a representative polyoxamide, poly(hexamethylene oxamide) (PA62) has good comprehensive performance. However, the high T m (330 C) creates an obstacle for processing. To improve the processability of PA62, poly(hexamethylene terephthalate/hexamethylene oxamide) alternating copolyamide (alt-PA6T/62) was synthesized by hexamethylene diamine-terminated 6T6-diamine and dibutyl oxalate via solution/solid state polycondensation. Random copolyamide (ran-PA6T/62) was also synthesized for comparison. The structure and properties of the copolymer were analyzed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Wide-angle X-ray diffraction (WAXD) and the saturated water absorption test. The NMR results confirm the alternating structure of alt-PA6T/62. The DSC and TGA results demonstrate that the novel alternating copolyamide alt-PA6T/62 (T m = 321 C, T 5 = 420 C) exhibited better thermal properties than those of ran-PA6T/62 (T m = 294 C, T 5 = 412 C). The saturated water absorption of alt-PA6T/62 was found to be 3.2 wt%. These results revealed that the novel alt-PA6T/62 had an alternating sequence distribution, showed a high melting point as well as good processability and thermal stability, and possessed low saturated water absorption and excellent dimensional stability.

Novel alternating copolyoxamides with high crystallinity and heat resistance

“…The unique double hydrogen bonding endows it excellent performance, [22][23][24][25] such as high heat resistance, low water absorption, good crystallization properties together with mechanical properties. With the increasing demand for high temperature resistant polyamides in recent years, polyoxamides have aroused more and more attention in industry [26][27][28][29][30][31][32] and academia [33][34][35] and have a good marketing prospects.…”

“…Additionally, it has further been reported that the relative insolubility of most polyoxamides prevents the formation of high molecular weight polymers when using conventional solution techniques. To obtain high molecular weight polyoxamides, a two stage procedure has been reported recently, [33][34][35] where a prepolymer is prepared at low temperature from a diester of oxalic acid and a diamine followed by solid state polymerization.…”

“…In contrast to the random copolymer with the same composition, the chain arrangement of the alternating copolymer is more regular, and the corresponding properties are principally much more desirable. Recently, patents [38][39][40][41] and literature 35,42 are reported in preparing copolyamides with alternating repeating units. The resulting copolyamides exhibit a strict alternating structure with outstanding properties.…”

New Strategy and Polymer Design to Synthesize Polyamide 66 (PA66) Copolymers with Aromatic Moieties from Recycled PET (rPET)

“…Furthermore, the configuration arrangement of the polyamide monomers greatly influenced the physical properties of the derived polymer. Random copolyamides often exhibit relatively low thermal properties and poor mechanical properties because the various irregular arrangements in the polymers undermine the regulated order of the molecular chain and limit the formation of inter- or intramolecular hydrogen bonds in the chains. , In contrast, alternating copolyamides often exhibit more excellent thermal properties, relatively low water absorption, and associated crystallization behavior because they have a more regular molecular chain arrangement . However, the polymerization process for the preparation of complete alternating copolyamides is difficult, uneconomical, and not easy to control …”

“…The utilization of BAHT-AA comonomer with PA66 salt as a major monomer for the synthesis of semiaromatic copolyamides has not been mentioned in the literature yet. In this current work, based on our previous reports, the semiaromatic diamine of BAHT has been successfully synthesized by the aminolysis reaction between PET waste and hexamethylenediamine (HMDA), ,,− which is deployed in the modification and synthesis of polyamides. Furthermore, the difference between the PA66/6T polyamides obtained by the conventional synthesis method and the PA66 copolyamides obtained by our method are systematically discussed under the same chemical structure composition and are compared with thermal analysis, wide-angle X-ray diffraction (WAXD), mechanical performance, crystallization kinetics, as well as relaxation and rheological behavior.…”