Preparation and properties of biobased polyamides based on 1,9-azelaic acid and different chain length diamines

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.