关键词: 聚酰胺66, 聚酰胺纤维, 金属氯化物, 氢键作用, 力学性能, 解络合

Abstract:

Objective Polyamide 66 (PA66) is widely applied in various fields due to its excellent mechanical strength, high toughness, and wear resistance. However, the high-density hydrogen bonds interaction between amide groups hinders its high level drafting, putting limits on the preparation of PA66 materials (especially fiber) with high mechanical strength. Metal chlorides can temporarily shield hydrogen bonds through complexation, thereby enhancing the stretchability of PA66. Subsequent decomplexation by water restores hydrogen bonds. Therefore, the complexation-stretching-decomplexation is a potential approach for preparing high strength PA66 fiber. This research aims to investigate the effects of CaCl₂ and LaCl₃, either individually or in combination, on hydrogen bonding interaction. Through shielding and restoration of hydrogen bonds, the mechanical properties of PA66 fibers were analyzed, providing an effective approach for preparing high performance PA66 fibers.
Method PA66/chloride composites with varying metal chloride contents were prepared through solution blending method. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) were used to investigate the regulation of hydrogen and its effects on PA66 crystallization properties. Based on these results, fibrous samples were fabricated by melt stretching method and subjected to mechanical property tests so as to analyze the effect of chloride-induced hydrogen bond shielding on properties. Finally, highly oriented samples obtained by stretching on tensile machine underwent decomplexation treatment to investigate the changes in fiber mechanical properties after hydrogen bond restoration.
Results CaCl₂ and LaCl₃, either individually or in combination, were found efficient in shielding the hydrogen bond interaction of PA66, leading to a significant decline or almost disappearance of the crystallization ability of PA66/chloride. The hydrogen bond shielding ability was found to follow the order of PA66-La/Ca > PA66-La > PA66-Ca, indicating a synergistic shielding effect when metal chlorides were loaded in combination. In terms of mechanical properties, metal chlorides significantly enhanced the stretchability of PA66 samples. The elongation at break of PA66-5La/Ca and PA66-10La/Ca increased remarkably, both exceeding 200%, which is 2-3 times that of pure PA66. The stress induced effect significantly increased the orientation degree of the samples and resulted in a transition from the α form to γ form. After 4-6 hours of water chelation treatment, the tensile strength of the samples with tensile orientation (but not broken) was increased to about 1.70 times its original strength due to the dual effects of high orientation and hydrogen bond recovery.
Conclusion CaCl₂ and LaCl₃ serve as effective complexing agents to shield hydrogen bond interaction in PA66, and both chlorides exhibit a synergistic effect in hydrogen bond shielding. This shielding demonstrates reversibility and adjustability. This method provides a simple approach for obtaining PA66 fiber products with high draw ratio and high strength.

Key words: polyamide 66, polyamide fiber, metal chloride, hydrogen bonding, mechanical property, decomplexation