In this study, our primary aim was to increase the presence of amine groups in polyamide 6 fibers. To achieve this, we employed a functionalization process that mainly depended on increasing the number of reactive sites via acid-catalyzed hydrolysis. The effects of several acids were rigorously examined, including hydrochloric acid (HCl), sulfuric acid (H2SO4), and formic acid (HCOOH). Following this comprehensive acid-based treatment, the method that demonstrated the most significant increase in amine groups was selected for further evaluation in dyeing experiments and full characterization. The quantification of amino groups was performed using potentiometry, evaluating the equilibrium state of acid removal from the fibers. To corroborate these results, the acid dye Levaset Blue 2R was employed, which measured the amount of dye bound to the fibers during the dyeing process. Characterization of the polyamide 6 fiber structural changes was conducted using multiple techniques, including tensile tests, Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). Among the acid treatments, the 11% HCl treatment exhibited the most significant increase in amine groups, amounting to an approximately 110% increase as measured by potentiometry and an approximately 150% increase using the dyeing method. During the dyeing process, the 11% HCl-treated fibers absorbed 91% of the dye from the dye bath, indicating enhanced color intensity and K/S value, thus affirming the efficacy of the amine group increasing. Tensile testing revealed a decrease in the strength of the functionalized fiber. In the FTIR spectra, there was a notable increase in the intensity of bands associated with the fiber's crystalline regions and hydrogen bonds. DSC tests validated the FTIR results, demonstrating a 9% increase in crystallinity. Furthermore, SEM micrographs depicted surface alterations induced by the hydrolysis process. These results collectively highlight the effectiveness of hydrolysis in introducing functional groups, enhancing color intensity during dyeing with acid dyes, and reducing dye content in the bath. Additionally, the potentiometric method for quantifying amine group demonstrated practicality and accuracy, serving as a valuable contribution to the field.

中文翻译：

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增强聚酰胺 6：酸水解进行官能化和氨基定量

在这项研究中，我们的主要目的是增加聚酰胺 6 纤维中胺基的存在量。为了实现这一目标，我们采用了一种功能化过程，该过程主要依赖于通过酸催化水解增加反应位点的数量。严格检查了几种酸的影响，包括盐酸 (HCl)、硫酸 (H2SO4) 和甲酸 (HCOOH)。经过这种综合酸基处理后，选择了胺基增加最显着的方法，用于染色实验和全面表征的进一步评估。使用电位测定法对氨基进行定量，评估从纤维中去除酸的平衡状态。为了证实这些结果，使用了酸性染料 Levaset Blue 2R，测量了染色过程中与纤维结合的染料量。使用多种技术对聚酰胺 6 纤维结构变化进行表征，包括拉伸测试、傅里叶变换红外 (FTIR) 光谱和差示扫描量热法 (DSC)。在酸处理中，11% HCl 处理表现出最显着的胺基增加，通过电位测定法测量，胺基增加约 110%，使用染色法测量，胺基增加约 150%。在染色过程中，11％HCl处理的纤维吸收了染浴中91％的染料，表明颜色强度和K/S值增强，从而证实了胺基增加的功效。拉伸测试显示功能化纤维的强度下降。在 FTIR 光谱中，与纤维结晶区和氢键相关的谱带强度显着增加。 DSC 测试验证了 FTIR 结果，表明结晶度提高了 9%。此外，SEM 显微照片描绘了水解过程引起的表面变化。这些结果共同强调了水解在引入官能团、增强酸性染料染色过程中的颜色强度以及降低浴中染料含量方面的有效性。此外，用于定量胺基的电位滴定法表现出实用性和准确性，为该领域做出了宝贵的贡献。