Wave behavior in the coating process of multilayer polymeric materials

A mathematical analysis model of multilayer viscoelastic fluids flowing dow n an inclined plane for any arbitrary wave numbers has been established to improve multilayer product quality in the coating processes. In the stabili ty study of the free surface with small elastic force, Reynolds number is t he primary parameter to induce surface instability for long and intermediat e waves. When the elastic force in either layer is large, elasticity can af fect the stability of long and intermediate waves. In addition, viscosity s tratification across the interface can also affect the stability of the fre e surface. For the interfacial stability of two-layer flow system, it is fo und that purely elastic instability occurs in most depth ratios for the who le spectrum of waves when the fluid with elasticity is placed as the inner layer next to the solid wall. In the study of stability for viscoelastic fl uid it demonstrates that arranging the more elastic and less viscous fluid as the outer layer leads to interfacial stability. In the more than three-l ayers investigation we found that placing the most viscous and least elasti c liquid as the innermost layer next to the solid wall and the least viscou s and most elastic liquid as the outermost layer next to the passive air ca n ensure the stability for the whole spectrum of waves.