Convection and diffusion assisted reactive coupling at incompatible semi-crystalline polymer interfaces

Abstract Based on a specifically designed stretching apparatus, we study the incidence of the stretching parameters on the formation of polypropylene-polyamide-6 (PP-PA6) copolymers acting as adhesion promoters in PP/PA6 multilayer films. The stretching apparatus mimics the stretching conditions found in the air gap of a co-extrusion machine in terms of stretching velocities and distances and of cooling rates. We propose a simplified numerical modeling of these experiments. It allows to explore how the various molecular (concentration in reactive species, diffusion coefficient) and stretching parameters affect the time evolution of the copolymer surface density during stretching. More precisely, we show that even though the contact time for the reaction is large regarding the reaction time, a dilation of the surface can result in a strong lowering of the grafting density at the interface.