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In this paper, the unsaturated hydrogen bonds (H-bonds) of the bio-based polyamide 56 (PA56) with an odd-even unit structure were analyzed by infrared spectroscopy. It was proved that the bio-based PA56 had less saturated H-bonds, which became attenuated and blue-shifted at the temperature exceeding 260°C. Besides, as H-bond was decayed and broken, new unsaturated H-bonds readily formed. Moreover, the experimental results obtained strongly indicate that the unsaturated H-bonds of bio-based polyamide 56 could react with polar metal oxides. Besides, the intercalation of montmorillonite was found to have a significant influence on the hydrogen bond between polymer chains.

This paper introduces a feasible method to improve the color value of bio-based polyamide 56 (PA56) fiber. Three types of whitening modifiers were introduced into the bio-based PA56 fibers by the in-situ polymerization method and melt blending method in order to improve the fiber color. The color values and mechanical properties of PA56 fibers were tested and analyzed and the optimum additive ratio and process conditions were discussed. The results show that the improved color value of bio-based PA56 fibers can be achieved by the melt blending method of fluorescent whitening masterbatch and reasonable spinning condition control. When the additive amount of fluorescent whitening agent is 0.3%, the index of lightness (L) increased from 84 to 90, while the yellow index (YI) reduced from 16.8 to 12.6. Moreover, PA56 fibers show high breaking strength about 4.27 cN/dtex and good yellowing resistance and durability.

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