A series of differently crosslinked polyacrylamide chelating resins were prepared, using N,N'-methylene-his-acrylamide as the crosslinking agent. The crosslinked resins were functionalized by the reaction with ethylene diamine to get amino group capacities varying from 4.2 to 1.1 mequiv/g. The maximum adsorption capacities of the lightly crosslinked resin for Fe3+, Fez+, Ni2+, and Cu2+ are 3.62, 4.22, 1.48, and 1.67 mequiv/g, respectively. The adsorbed metal ions can be quantitatively desorbed. The adsorption rate and the influence of pH on the adsorption of metal ions were examined. The resins can be used for the separation between different metal ions as well as the ions in different valence states (e.g., Fe3+ and Fez+). The resin is amenable for continuous process and can he regenerated several times.

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The objective of the present work is to develop a novel type of structurally modified benzoxazines with improved performance characteristics using imidazole core based diamine with formaldehyde and different types of phenolic compounds in order to utilize them for high-performance applications. In this work, an attempt has been made to bring down the polymerization temperature of the benzoxazine monomers, which is one of the most deficient factor restrict the applications of benzoxazines, when used in the form of adhesives, sealants, encapsulants, and matrices with other substrates, though they possess numerous advantages and valuable properties than those of other available thermosets. In this context, in this study, two approaches have been adopted to bring down the polymerization temperature, viz., (i) the development of structurally modified benzoxazine monomers with imidazole core and (ii) an incorporation of varying nature of chemical compounds as catalysts, to lower the polymerization temperature and to enhance the thermal stability and char yield. Three types of benzoxazines were developed using imidazole core based diamine with monohydric phenols and formaldehyde, at appropriate conditions. The molecular structure of benzoxazines was confirmed from Fourier transform infrared spectroscopy and 1 H-nuclear magnetic resonance analysis. From data, it was observed that the imidazole diamine based benzoxazines prepared from 1-naphthol exhibits lower curing temperature of about 192 8C than that of other samples studied in this work. In addition, the influencing effect of catalysts viz., 4-hydroxy acetophenone, 4-hydroxy benzaldehyde, 4hydroxyphenyl maleimide, and thiodipropionic acid (TPA) on thermal properties of benzoxazines also was studied. Among the catalysts, it was found that the TPA is the most efficient catalyst. In the case of imidazole diamine based benzoxazines prepared from cyanophenol, the TPA reduces value of polymerization temperature (T p ) from 217 to 167 8C. The thermogravimetric analysis indicates that thermal stability of the benzoxazines are improved to a significant extent when 10 wt % catalysts were incorporated into the system.

Size exclusion chromatography (SEC) has been used to study the influence of molecular weight on the reactivity of the hydroxyl group in free radically polymerised hydroxyl‐terminated polybutadiene (HTPB). The HTPB prepolymer was converted into a UV‐absorbing urethane derivative by reaction with phenylisocyanate and the degree of conversion was followed from the UV/DRI (Differential Refractive Index) signal of the derivative using dual detector SEC. Though the overall reaction levelled off at about 70% conversion at room temperature, the time taken by different molecular weight species to attain this level was different. The computed rate constants were larger for the higher molecular weights in a given sample. This is attributed to the polyfunctionality of the higher molecular weight species.