KAO Germany GmbH, Darmstadt, Germany.
KAO Corporation, Tokyo, Japan.
Int J Cosmet Sci. 2022 Oct;44(5):555-568. doi: 10.1111/ics.12806. Epub 2022 Aug 12.
The process of moisture sorption and desorption by human hair was analysed for extracting hints on the hair structure.
The isotherms of moisture sorption and desorption by hair were recorded for untreated and chemically treated (permed and bleached) hair. Data of swelling were also considered.
By examining the swelling and moisture sorption of keratin fibres, it is possible to conclude that hysteresis is quite improbably caused by capillary condensation. The mobility of the protein chains and the strength of the bonds binding water molecules to the active sites inside the matrix are proposed as causes instead. The concept of "breaking symmetry", derived from moisture sorption- desorption data, and the method of evaluating this parameter, is proposed as a way of characterizing the chemical treatment of hair. The results show that bleaching produces a larger breaking of symmetry than perming, and this is suggested to be due to new hydrogen bonds, created as a result of the chemical treatment, replacing the original disulphide bonds, which are of different strength compared to the bonds of untreated hair. The quantitative sorption data matched well to the model of grains of matrix enveloped in layers of water molecules at increasing relative humidity, up to 100%. The analysis suggested that, aside from the glass transition event occurring at around 60%-70% relative humidity, there is another, less examined, transition occurring at around 30% relative humidity, assigned to the opening of the hair inner structure, and accommodation of more water molecules. Both transitions are reflected by corresponding changes in the fibre mechanical behaviour.
The moisture sorption-desorption by hair was shown to not only allow a quantitative differentiation among various cosmetic treatments of the hair but to also provide valuable information on the structure of the fibre.
通过分析人体毛发的吸湿和解吸过程，提取有关毛发结构的线索。
记录未经处理和经化学处理（烫发和漂白）的毛发的吸湿和解吸等温线。还考虑了膨胀的数据。
通过检查角蛋白纤维的膨胀和吸湿，可以得出结论，滞后现象不太可能是由毛管冷凝引起的。相反，建议将蛋白质链的移动性和将水分子结合到基质内部活性位点的键的强度作为原因。从吸湿-解吸数据得出的“打破对称性”的概念以及评估该参数的方法被提出作为一种表征毛发化学处理的方法。结果表明，漂白比烫发产生更大的对称性破坏，这被认为是由于新的氢键形成，作为化学处理的结果，取代了原始的二硫键，其强度与未经处理的毛发的键不同。定量吸附数据与在不断增加的相对湿度下，被水分子层包裹的基质颗粒的模型很好地匹配，直至 100%。分析表明，除了在相对湿度约 60%-70%处发生玻璃化转变事件外，还有另一个不太被检查的转变发生在相对湿度约 30%处，该转变被分配到毛发内部结构的打开，并容纳更多的水分子。这两个转变都反映在纤维机械性能的相应变化中。
毛发的吸湿和解吸不仅允许对头发的各种美容处理进行定量区分，而且还提供有关纤维结构的有价值信息。
