ABSTRACT:The interpenetrating polymer network hydrogels based on poly(vinyl alcohol) were obtained by graft copolymerization of acrylamide and styrene onto polyvinyl alcohol in the presence of N,NЈ-methylene bisacrylamide as a crosslinking agent. The hydrogels were characterized by optical microscopy, scanning electron microscopy, infrared spectral analysis, differential scanning calorimeter, and thermogravimetric analysis. The hydrogels showed enormous swelling in aqueous medium and displayed swelling characteristics, which were highly dependent on the chemical composition of the hydrogels and pH of the swelling medium. The kinetics of water uptake and the mechanisms of water transport were studied as a function of composition of the hydrogel and pH of the swelling medium.
The Asiatic clam (Corbicula fluminea) has become a pest to many users of freshwater transmission systems. Monochloramine has been suggested as a biocide because it is effective and the formation of trihalomethanes is low (see the article on page 53 of this issue). Flow‐through aquariums, a laboratory incubator, and a pilot‐scale pipeline were used to show that monochloramine concentrations between 1 and 10 mg/L effectively killed juvenile clams over a wide range of water temperatures, with mortality increasing significantly with temperature. The reduction in clam mortality as water temperature decreases can be overcome by corresponding increases in biocide concentration. An equation is provided that predicts the kill that would be achieved at a given biocide residual and water temperature. The pH did not affect the efficacy of the biocide.
Six unfractionated samples of polyacrylamide were hydrolysed to varying extents. The partially hydrolysed polyacrylamides were investigated by viscosity, osmotic pressure and light scattering techniques in 0,12 M NaCl. The molecular weights of the hydrolysed polyacrylamides confirmed the absence of main chain degradation during hydrolysis. Intrinsic viscosities and dimensions increased with increasing extent of hydrolysis. On correlating the intrinsic viscosities with the extent of hydrolysis, a linear relationship between intrinsic viscosities and the squareroot of the extent of hydrolysis was obtained. a) NCL Communication No. 3325
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