2017 年 41 巻 3 号 p. 115-127
A Synthetic Stratum Corneum (SSC) was produced from a mixture of PVA (poly vinyl alcohol) hydrogel and SDS (sodium dodecyl sulphate) surfactant, later mixed with rapeseed oil and, finally crosslinked with glutaraldehyde. The thermal properties of the material were studied via TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry) measurements and the composition was analysed by FTIR (fourier transform infrared). The hydration degree of the SSC measured at 30% of relative humidity and 25°C was 23% whilst at wet conditions it grew up to the 80%. Moreover, the surface adhesion of the SSC, evaluated under dry, normal and wet conditions indicated substantial variations depending on the skin conditions with values for the work of adhesion of -16, -122.4 and -233.4 mN/m, respectively. The viscoelastic properties of the material were also evaluated by tensile tests and stress relaxation measurements. The elastic modulus of the samples was found between 8.8 - 1.9 and 3.3 - 1.2 for dry and wet conditions, respectively. Further, stress relaxation times of 64.4 sec and 83.2 sec were calculated from the SLS (standard linear solid) model at dry and wet conditions, respectively. Lastly, the SSC presented a frictional performance in close agreement to that of human skin under normal (36% relative humidity and 25°C) and wet conditions. The friction coefficient, measured between 1 and 50 mN, was found between 0.8 to 0.45 at dry conditions whereas, at wet conditions, it ranged between 2 and 0.45. At higher applied forces between 0.5-3.5 N, the friction coefficient was nearly steady with values of 0.4 and 0.55 for dry and wet conditions, respectively.