Authors: T.H. Liu, C.L. Huang, S. Lee
Affilation: National Tsing Hua University, Taiwan
Pages: 287 - 290
Keywords: wrinkle pattern, polymer film, chemical stress, solvent
The wrinkle pattern on polymeric surface is explained by chemical stresses. We solved the anomalous transport equation to obtain the concentration of solvent in polymeric film. The anomalous transport consists of case I and case II transport. From the concentration distribution, we calculated the chemical stresses in the specimen. Then we found the total mechanical energy including bending, stretching, and solvent-induced stresses. The wrinkle pattern appears when the total energy is negative. Based on this criterion, we derived the wrinkle wavelength as a function of specimen thickness and uptake period, desorption time, and resorption time of solvent. Fig.2 shows the wrinkle wavelength as a function of temperature and absorption time where the solid and dashed lines are obtained from the theory and experiment, respectively. The experimental data are in good agreement with the modelling prediction for short absorption times, but the former is slightly greater than the latter for long times. The wavelength is increased with increasing absorption time and temperature. The compression stress increases with uptake period. The formation of wrinkle pattern is required both compressive stress on the surface layer and rigid substrate. The desorption and resorption are necessary conditions to produce the wrinkle pattern, but not sufficient.