Enhancement of interfacial adhesion between polystyrene and styrene maleic anhydride random copolymer via reactive reinforcement

The effects of amine-terminated polystyrene (omega-amino-PS) of various molecular weights on the interfacial adhesion strength between polystyrene and styrene maleic anhydride (SMA) random copolymer have been investigated. The adhesive joint is composed of SMA and a blend of PS and omega-amino-PS, in which the omega-amino-PS acts as a reactive compatibilizer. Here, the amine end-group of omega-amino-PS in the PS/omega-amino-PS blend is known to react with the anhydride group of SMA and form an end-grafted copolymer, which acts as an interlinking molecule across an interface and improves the interfacial adhesion strength. The fracture toughness of the interface was measured using a modified double-cantilever beam fracture test. The enhancement of fracture toughness of the interface was evaluated as a function of molecular weight and content of omega-amino-PS, i.e. interlinking chain length and area density of interlinking molecules. The fracture toughness was found to increase with the amount of omega-amino-PS and then decreased or saturated at a certain content depending on the molecular weight of omega-amino-PS. When the molecular weight of omega-amino-PS was 26 000 (26 k), which is just above the entanglement molecular weight, there was an optimum content in reinforcing the interfaces due to the weak mechanical strength of 26 k omega-amino-PS. However, when the molecular weight was far above the entanglement molecular weight, i.e. 67k and 127k, the fracture toughness levelled off as the content of omega-amino-PS increased. At the same concentration of amine groups, 127k omega-amino-PS showed the highest fracture toughness. (C) 1997 Elsevier Science Ltd.