Papir Y S, Hsu K H, Wildnauer R H
Biochim Biophys Acta. 1975 Jul 14;399(1):170-80. doi: 10.1016/0304-4165(75)90223-8.
The tensile properties of the outermost layer of skin of neonatal rats, the stratum corneum, were investigated at a constant strain rate as a function of moisture content and ambient test temperature. The results show that the mechnical behavior of this membrane, whose primary constituent is the fibrous protein keratin, can be significantly altered by variations in both the sorbed water content and ambient temperature. In particular, a brittle to ductile transition was observed at 25 degrees C once the hydration level exceeded 70% relative humidity. Similarly, an identical phenomenon was detected at temperatures beyond 40 degrees C for specimens whose equilibrium moisture concentrations were maintained at 10 g H2 O/100 g dry protein. Differential scanning calrimetry measurements showed the presence of a molecular relaxation process which migrated from 42 degrees C at 40% relative humidity to --18 degrees C at 95% relative humidity. It is postulated that this relaxation process, possibly corresponding to the glass transition of the fibrous protein component of stratum corneum, is primarily responsible for the observed behavior.
以恒定应变率研究新生大鼠皮肤最外层（角质层）的拉伸性能，该性能是水分含量和环境测试温度的函数。结果表明，这种主要由纤维蛋白角蛋白构成的膜的力学行为，会因吸附水含量和环境温度的变化而显著改变。特别是，当水合水平超过70%相对湿度时，在25摄氏度下观察到从脆性到韧性的转变。同样，对于平衡水分浓度保持在10 g H₂O/100 g干蛋白的标本，在温度超过40摄氏度时也检测到相同现象。差示扫描量热法测量显示存在一个分子松弛过程，该过程从相对湿度40%时的42摄氏度迁移到相对湿度95%时的-18摄氏度。据推测，这个松弛过程可能对应于角质层纤维蛋白成分的玻璃化转变，主要负责所观察到的行为。
