I was asked Why PP-PE are not compatible and what is the layer blending chemistry criteria? I.e Nylon + EVOH need no Tie but Nylon + pp or PE or EVOH +PP OR PE need tie resin for multi layer extrusion process. I am not sure if anyone really knows whey PE and PP are not compatible as compared to small molecules which do dissolve in each other, but it goes back to the Gibbs free energy change on mixing.




