Some properties of styrene-based ionomers II

Some properties of styrene-based ionomers obtained from copolymers styrene (S) and acrylic acid (AA) or methacrylic acid (MA) obtained in emulsion containing alkali metal salts have been investigated. A study has been conducted to examine the influence of the acid content and nature (acrylic or methacrylic) and nature of alkali metal salt on the glass transition temperature, density, melt index, and activation energy of flow of the styrene-based ionomers. The present studies have indicated that the temperature of glass transition (T-g) of sodium ionomers increases as the sodium content rises, but the increase is lower than in the case of the ionomers based on copolymers obtained in bulk. The density of films rises with the content of alkali metal salt introduced to the polystyrene chain, and it is higher than in the case of the ionomers based on copolymers obtained in bulk containing almost the same content of alkali metal salts. Styrene ionomers containing alkali metal acrylates have higher densities than those containing alkali metal methacrylates. The melt index of the investigated ionomers depends on the amount and type of introduced acid and salt, as well as on the molecular weight of the initial copolymer. (C) 2005 Wiley Periodicals, Inc.