Insights on the Hair Keratin Structure Under Different Drying Conditions

ABSTRACT

It is important to understand the patterns of hair keratin integrity caused by drying methods. No previous information exists in the literature to compare different drying conditions needed to assess physical changes in the hair keratin. We used human hair for these experiments. We found that different drying conditions greatly influence the wearing fatigue of the hair fibers. Using a microfiber towel (80% polyester/20% nylon) to remove the excess water seems to better retain the integrity of human hair when compared to drying with a blow-drier or a cotton towel. Hair dried with a microfiber towel showed strong intensity bands at 1664 cm-1 consistent with an alpha-helix structure, while these bands were absent in the spectrum of the hair dried with a blow-drier or a cotton towel. Fatigue recovery of the hair sample dried with a microfiber towel showed much higher wear resistance when compared with the cotton towel and blow-drier processes. These findings were supported by FTIR (Fourier transform infrared) which aided in the elucidation of the secondary structure of alpha-keratin and its effect in the stabilization of hair fibers. When hair samples were exposed to high temperatures, DSC (Differential Scanning Calorimetry) profiles provided information about the movement of water molecules from the fiber, being the enthalpy for hair dried with microfiber towel the highest value. Contributions from damage, friction, and heat were correlated with the molecular structure, in particular, the alpha-helixes predicting that drying condition using a microfiber towel is the process that better preserves hair integrity.

GRAPHICAL ABSTRACT

摘要

了解干燥方法引起的头发角蛋白完整性的模式很重要. 文献中没有以前的信息来比较评估头发角蛋白物理变化所需的不同干燥条件。我们用人的头发做这些实验. 我们发现，不同的干燥条件对头发纤维的穿着疲劳有很大影响. 与用吹风机或棉毛巾干燥相比，用超细纤维毛巾（80%聚酯纤维/20%尼龙）去除多余的水分似乎能更好地保持头发的完整性. 用超细纤维毛巾干燥的头发在1664 cm-1处显示出与α-螺旋结构一致的强强度带，而用吹风机或棉毛巾干燥的毛发的光谱中不存在这些带. 与棉毛巾和吹风机工艺相比，用超细纤维毛巾干燥的头发样品的疲劳恢复表现出更高的耐磨性. 这些发现得到了傅立叶变换红外光谱（FTIR）的支持，该光谱有助于阐明α角蛋白的二级结构及其在头发纤维稳定中的作用. 当头发样品暴露在高温下时，DSC（差示扫描量热法）图谱提供了关于水分子从纤维中移动的信息，用微纤维毛巾干燥头发的焓值最高. 损伤、摩擦和热量的贡献与分子结构有关，特别是α螺旋预测，使用超细纤维毛巾的干燥条件是更好地保持头发完整性的过程.

KEYWORDS:

• Keratin fiber
• FTIR microscopy
• wear resistance
• alpha-helix
• hair damages
• molecular structure

关键词:

• 角蛋白纤维
• 显微镜
• 耐磨性
• α螺旋
• 毛发损伤
• 分子结构

Acknowledgements

This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Highlights

• different drying conditions deeply affect the wearing fatigue of human hair;

• drying condition with a microfiber towel preserves the alpha-keratin structure of the keratin fiber;

• microfiber towel exhibited higher mechanical wear resistance 45% higher than cotton towel or blow-drier.