PA6T/66 and PA5T/56 with stable molecular weight and molecular weight distribution were prepared by one-step polymerization. The relationship between the structure and physicochemical properties of two kinds of polyamide samples was analyzed by software analysis and instrument test. The results show that the hydrogen bond between molecular chains has a significant effect on the properties of the materials. From the microscopic point of view, the mechanical properties of PA5T/56 molecular model were generally better than those of PA6T/66 molecular model because the hydrogen bond was not considered. At the macro level, the result was just the opposite because of the hydrogen bonds between the molecular chains. The Gibbs free energy of PA5T/56 dehydration condensation reaction was larger, indicating that the polymerization rate was faster, which was consistent with the actual situation. PA6T/66 belongs to the triclinic α crystal system, PA5T/56 belongs to the hexagonal γ crystal system, PA6T/66 T g = 105.50℃, T c = 257.34℃, T m = 295.74℃, the ΔG PA6T/66 and ΔG PA5T/56 = 36.84 kJ/mol and 34.27 kJ/mol respectively indicate that the heat resistance and thermal properties of PA6T/66 were better than those of PA5T/56.
In this paper, the polycondensation kinetics of bio-based semi-aromatic high-temperature polyamide PA5T/56 was studied in a micro-high-temperature and high-pressure reactor. The polycondensation experiment of PA5T/56 salt solution with temperature of 240–300 ℃ and initial water content of 5–30wt% was carried out. The change of end group content in the reaction process was investigated, and the relationship between polymer equilibrium molecular weight and temperature and water content was explored. The results showed that the end group concentration decreased rapidly at the beginning of the reaction and approached equilibrium after a period of time, and the higher the temperature, the higher the initial water content and the lower the equilibrium molecular weight, indicating that the polycondensation of PA5T/56 was an exothermic reaction; on this basis, a kinetics model of polycondensation reaction was established based on the literature model, it was considered that the polycondensation reaction is an acid-catalyzed third-order reaction, and the effects of temperature and water content on the equilibrium and rate of polycondensation reaction can be investigated. The kinetics model of polycondensation reaction was obtained, and the calculated results of the model were basically consistent with the experimental values.
Bio-based semi aromatic high temperature polyamide PA5T/56 was synthesized by one-step high temperature and high pressure solution polymerization with bio-based monomer pentanediamine. The non-isothermal crystallization behavior of PA5T/56 was studied by differential scanning calorimetry (DSC). Mo equation was used to describe the non-isothermal crystallization kinetics. The activation energy of non-isothermal crystallization was calculated by Kissinger equation. The effect of benzene ring (T) molar content on the non-isothermal crystallization kinetics was investigated. The crystal morphology was observed by optical polarized microscope (POM) and X-ray diffraction (XRD). The results showed that the non-isothermal crystallization activation energy and absolute crystallinity of nylon 5 T/56 first increased and then decreased with the increased of T molar content from 25% to 32.5%. At the same time, the crystal form of polyamide didn’t change. When the molar content of T was 30%, the number of spherulites was the largest, the size was the smallest, the crystallization rate was the fastest, and the crystallization ability was the highest, which indicated that T can play a role in promoting crystallization in polymer molecular chain.
Jiaying Liu,Guang Nie,Shuai Yang,Yanmin Zhang,Ziyun Li,Sitong Wang,Zijian Song,Shuanli Du,Yingchun Li
Semi-aromatic polyamides (SAPAs) are emerging as promising engineering polymers due to their unique combination of high rigidity, thermal stability, and processability. However, pure SAPAs suffer from limited electrical conductivity and multifunctional responsiveness, hindering their application in smart materials and actuators. In this paper, PA5T/56 copolyamides with varying terephthalic acid/adipic acid molar ratios (3/7–7/3) were synthesized via melt polycondensation and characterized mainly by 1 H NMR, FTIR. PA5T/56 (3/7), with the optimal balance of mechanical performance and processability, was selected as the composite matrix. Composites containing different contents of carboxyl-functionalized multi-walled carbon nanotubes (MWCNT-COOH, 0, 5, 10, 15 wt%) were prepared by solution casting. The effects of MWCNT-COOH on the thermal stability, mechanical properties, and especially thermo- and electro-induced shape memory behaviors of the composites were comprehensively investigated. The results show that MWCNT-COOH markedly improves the thermo-induced shape memory at an appropriate loading, with the shape recovery rate reaching 82.8% and the shape fixity rate exceeding 90% at 10 wt% MWCNT-COOH. 15 wt% MWCNT-COOH/PA5T/56 can achieve electro-induced shape recovery via Joule heating within 44 s. Overall, this work establishes the structure–property relationships of PA5T/56 copolyamide with tailored monomer compositions and demonstrates the effectiveness of MWCNT-COOH in imparting thermo- and electro-responsive functionalities.
危险品化学品经营许可证（带存储）