Influence of surface charge on the formation of the carbonized layer relief on the polymer surface during ion-plasma treatment

The origin hypothesis of the wavy relief on the surface of plasma-treated polyurethane is considered in this paper. It has been suggested that stresses and strains appear due to the eponymous charge accumulated in the near-surface layer. A technique for calculating stresses under the condition of a uniform charge distribution is proposed. The constitutive equations of an elastic medium with a distributed charge, based on the law of conservation of energy and thermodynamic inequality, are obtained. The Cauchy stress tensor contains a term that depends on the charge distribution density in the resulting equations. A calculation, showing the dependence of the magnitude of stresses on energy and fluence of implanted ions, has been carried out. According to the proposed model, calculations show that the stresses in the material are high enough to cause a change in the shape of the surface at certain treatment regimes. It is shown that the loss of stability and, as a consequence, the appearance of waves on the surface of the material is typical for low-modulus polymers. The calculation results are compared with real images, obtained using optical and atomic force microscopes, of the samples surfaces after the treatment. Conclusions about the viability of the proposed hypothesis are drawn.