(298g) Effects of Flow and Interfacial Block Copolymer on Polymer-Polymer Adhesion

Modern polymeric products typically consist of at least two polymer phases. However, nearly all polymer pairs are immiscible thus they have very poor interfacial adhesion. We found that processing flow can decrease adhesion even further. For a polystyrene (PS)/ poly(methyl methacrylate) (PMMA) multilayer extrudate, the adhesion showed nearly a three-fold decrease when the shear stress experienced exceeds the level where interfacial slip is expected to be significant (Zhang et al J. Rheol. 2006). Full interfacial strength recovered rapidly upon static annealing. Block copolymers formed through reactive coupling of functional polymers premixed with layers can prevent the adhesion decrease during coextrusion. Moreover, the chemical bonding introduced by those copolymers can work as interfacial bridges to strengthen interfaces. Direct correlation between adhesion promotion and the number of block copolymer chains at the interface was studied and an energy model is proposed to describe this behavior.