The Synthesis And Properties Of Water-Disintegrable Polystyrene

A series of sodium polyacrylate with different water-absorbency andsuperabsorbent copolymers based on sodium acrylate were prepared by inverseemulsion polymerization. Styrene, surfactant and superabsorbent polymers weremixed and the in-situ blend polymerization of styrene was carried out when theinitiator benzoperoxide was added. The foamed water-disintegrable polystyrenes wereprepared by "two-step" process.Results show that the blends containing polystyrene and superabsorbentpolymers tend to disintegrate easily with the increase of the content of superabsorbentpolymers and the decrease of the relative molecular weight of PS. When the relativemolecular weight of PS is constant, the blends exhibit excellent water-disintegrableproperties resulting from the high water-absorbency of the sodium polyacrylate. Whenacrylic acid in superabsorbent polymers is neutralized partly, the resulting blends alsoexhibit excellent water-disintegrable properties obviously.A lot of superabsorbent copolymers were synthesized by copolymerizing2-acrylamido-2-methylpropanesulfonic acid (or sodium sulfonate) or sodiumallylsulfonate, acrylamide and sodium acrylate, and consequently the blends includingthese superabsorbent copolymers were prepared. Compared with the blendscontaining homopolymers sodium polyacrylate, the blends containing superabsorbentcopolymers based on 2-acrylamido-2-methylpropanesulfonic acid (or sodiumsulfonate) which synthesized using the same content of initiator and crosslinker asthat of homopolymers exhibit better water-disintegrable properties. The adding ofsuperabsorbent resins from sodium allylsulfonate, acrylamide and sodium acrylate towater-disintegrable polystyrene blends has little benefit to improve thewater-disintegrable properties of the blends, although the water-absorbency of theresins are considerable. The superabsorbent polymers from the copolymerization of methacryloloxyethyltrimethylammonium chloride and sodium acrylate have salt-resistant properties. Theblends of polystyrene and these superabsorbent resins show bad water-disintegrableproperties in de-ionized water or salt media resulting from lower water-absorbency ofsuperabsorbent polymers.When the content of Span-80 is 3%, the blends of polystyrene and sodiumpolyacrylate exhibit the best water-disintegrable properties. When the superabsorbentpolymer, in which 90% acrylic acid is neutralized, is added to the resulting blends, theproperties of water-disintegrable polystyrene are improved with the increase of thecontent of Span-80. As the conclusion shows, the optimum content of Span-80depends on the kind of superabsorbent polymers.The blends of polystyrene and sodium polyacrylate exhibit different properties ofhygroscopicity in saturated vapor pressure of water or air. The sample, of which therelative molecular weight of PS is low or the content of superabsorbent polymers ishigh, tends to water-disintegrate and exhibits poor anti-hygroscopicity.The foamed water-disintegrable polystyrenes were studied by "two-step"foaming method. The water-disintegrable properties of the foamed blends are lessthan those of unfoamed materials because of the changing of the distribution of thesuperabsorbent polymers and Span-80.