Synthesis and Characterization of Fatty Polyamide from Dimer Acid Prepared from Afzelia Africana seed oil

Abstract

Afzelia africana seed oil was extracted from its oil-bearing seeds via soxhlet extraction with n-hexane as the solvent. The oil was characterized and the percentage yield, specific gravity, refractive index, iodine value, acid value and saponification value were; 24.6%, 0.9184, 1.4708, 105.75 (Wij’s), 5.61 (mg KOH/g) and 199.155 (mg/KOH/g) respectively. Dimer acids were synthesized by heating 50g of the oil at 3400C in nitrogen inert atmosphere using iodine crystals as catalyst. Characterization of the dimer acid indicated that refractive index, iodine value, acid value and saponification value were 1.4904, 126.90 (Wij’s),7.01 (mgKOH/g) and 136.043 (mgKOH/g) respectively. Fatty polyamide was synthesized by heating the dimer acid and ethylenediamine at a temperature of 2100C in an inert atmosphere. Fourier Transform Infrared spectroscopy (FTIR) analysis for both the synthesized dimer acid and fatty polyamide was obtained. The dimer acid shows a peak at 1697.41cm-1 due to C=O stretch of carboxylic acid, a peak at 1080.17 cm-1 which corresponds to O-H bend of carboxylic acid. A peak corresponding to C-H stretch of alkane group shown at 2916.42 cm-1, a peak at 1111.03 cm-1 due to C-O-C stretch of fatty ester group. The polyamide showed a peak at 1180.47 cm-1 which corresponds to C-N stretch of aliphatic amine group. The significant difference in absorption between the synthesized dimer acid and fatty polyamide is the peak at 3533.71 cm-1 which corresponds to amide N-H stretching absorption that was present in the polyamide due to the higher number of hydrogen bonds formed by amide groups. The findings revealed that Afzalia africana seed oil is semi-drying in nature based on its iodine value and has the desirable qualities needed for producing surface coating vehicles.