A series of environmentally friendly polyamides (PA69, PA109 and PA129) have been synthesized by carrying out step-melting polycondensation reactions of bioderived monomers: 1,9-azelaic acid with different chain length diamines, respectively. Their molecular structure and chemical composition have been characterized using elemental analysis (EA), Fourier transform infrared (FTIR) and proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy. Their crystal structures, mechanical properties, thermal behaviors and moisture absorption properties have also been investigated. The number-average molecular weights of PA69, PA109 and PA129 were 51,300, 38,900 and 38,500, respectively, and the main crystal structures of them were α -crystalline and γ -crystalline form. As the length of diamine increased, the melting temperatures of them were from 214 to 203 to 195 °C, respectively, and the crystallization temperatures of them were from 176 to 166 to 161 °C, respectively. The bending strengths of them were determined to be 102.58 MPa, 84.11 MPa, 65.91 MPa, respectively, and the izod impact strengths of them were 9.24 kJ/m 2 , 8.82 kJ/m 2 , 8.54 kJ/m 2 , respectively. They were also found to absorb less moisture than PA6 and PA66.

中文翻译：

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1,9-壬二酸和不同链长二胺基生物基聚酰胺的制备及性能

通过将生物衍生单体1,9-壬二酸与不同链长的二胺分别进行分步熔融缩聚反应，合成了一系列环保型聚酰胺（PA69、PA109和PA129）。它们的分子结构和化学组成已使用元素分析 (EA)、傅里叶变换红外 (FTIR) 和质子核磁共振 ( 1 H-NMR) 光谱进行表征。还研究了它们的晶体结构、机械性能、热行为和吸湿性能。PA69、PA109和PA129的数均分子量分别为51300、38900和38500，主要晶体结构为α-晶型和γ-晶型。随着二胺长度的增加，它们的熔融温度分别为214～203～195℃，结晶温度分别为176～166～161℃。它们的弯曲强度分别为102.58 MPa、84.11 MPa、65.91 MPa，悬臂梁冲击强度分别为9.24 kJ/m 2 、8.82 kJ/m 2 、8.54 kJ/m 2 。还发现它们吸收的水分少于 PA6 和 PA66。