Efect of Alkali Metals and Alkaline Earth Metals Hydroxides on the Structure of Wool Fibers M. Abou Taleb a , S. Mowaf a , C. Vineis b , A. Varesano b , D.O. Sanchez Ramirez b , C. Tonetti b , and H. El-Sayed a a Industrial Textile Research Division, National Research Centre, Giza, Egypt; b CNR-STIIMA, National Research Council- Institute of Intelligent Industrial Technologies and Systems for Advanced Manufacturing, Biella, Italy ABSTRACT Wool is sensitive toward the efect of alkaline solutions which are usually used in the dissolution of wool fbers to regenerate keratin. In this investiga- tion, the efect of diferent alkalis on the chemical composition and the secondary structure of wool was studied. Wool was treated with equivalent amounts of alkali metal hydroxides (lithium, sodium, and potassium hydro- xides) as well as alkaline earth metal hydroxides (strontium and barium hydroxides). The efect of these alkalis on wool was monitored using amino acid analysis, elemental analysis, carboxylic content, acid, and base combin- ing capacity, urea-bisulfte and alkali solubility, and FTIR spectroscopy. Further structure elucidation was conducted by thermo-gravimetric analysis, diferential scanning calorimetry, and X-ray difraction pattern. Scanning electron microscopy was used to assign the alteration of the fber morphol- ogy of the alkali-treated wool. The results of this investigation indicate that the efect of the used alkalis on wool is not similar. Cystine, glycine, and the basic amino acids are the most afected species in the treated wool. Some elimination reactions were involved during alkaline treatment of wool; namely decarboxylation, desulphydration, and deamination. The secondary structure of wool treated with Sr(OH) 2 and Ba(OH) 2 was changed from the α- helical structure into the β-sheet form. 摘要 羊毛对碱性溶液的影响很敏感, 碱性溶液通常用于溶解羊毛纤维以再生角 蛋白. 研究了不同碱对羊毛化学成分和二级结构的影响. 羊毛用等量的碱金 属氢氧化物 (锂、钠和氢氧化钾) 以及碱土金属氢氧化物 (锶和钡氢氧化物) 处理. 采用氨基酸分析、元素分析、羧基含量、酸碱结合力、亚硫酸氢钠 和碱溶解度、红外光谱等方法, 研究了这些碱对羊毛的影响 ° 通过热重分 析、差示扫描量热法和X射线衍射图对其结构进行了进一步的分析. 用扫 描电镜观察了碱处理羊毛纤维形态的变化. 研究结果表明, 所用碱对羊毛的 影响并不相似. 胱氨酸、甘氨酸和碱性氨基酸是处理过的羊毛中受影响最 大的种类. 在羊毛碱处理过程中, 涉及到一些消除反应, 即脱羧、脱硫和脱 氨. 经 Sr (OH) 2 和 Ba (OH) 2 处理后, 羊毛的二级结构由 α-螺旋结构转变 为 β-片状结构. KEYWORDS Wool; keratin; macromolecule; fibers; alkali; characterization; chemical composition 关键词 羊毛; 角蛋白; 高分子; 纤 维; 碱; 特征化; 化学成分 Introduction Keratins are fbrous proteins, which are the main constituents of wool fbers. Keratin has high stability, distinctive physical properties, and resistance to chemical attacks due to the presence of inters- and intermolecular disulfde bonds of cystine amino acids in the wool structure (Cardamone 2010). CONTACT H. El-Sayed hosam@trdegypt.org Industrial Textile Research Division, National Research Centre El-Behouth St., Dokki, El-Behouth St., Dokki, Giza 12622, Egypt. JOURNAL OF NATURAL FIBERS https://doi.org/10.1080/15440478.2020.1846659 © 2020 Taylor & Francis