Formation of diblock copolymers at PP/PA6 interfaces and their role in local crystalline organization under fast heating and cooling conditions

Multilayer polypropylene/polyamide 6 (PP/PA6) films are commonly obtained by co-extrusion, with PP/PA6 interfaces reinforced through diblock PP/PA6 copolymers formed in situ by the reaction of maleic anhydride modified PP on the NH2 end-groups of PA6 molecules at the contact between the two molten polymers. We present procedures allowing one to form PP/PA6 thin films assemblies in thermal conditions (fast heating and cooling kinetics, short annealing times) representative of typical co-extrusion conditions. Selective dissolution of the PA6 part of the assemblies permits to first dose the surface density of copolymer, and second to analyze by AFM imaging the incidence of the copolymer surface density on the crystalline morphology at the interface. These experiments are a first step toward the identification of the key parameters controlling the fracture toughness in these multilayer films.