Six types of anionic starch derivatives, viz. carboxymethyl starch, carboxyethyl starch, poly(acrylic acid)‐starch graft copolymer, starch‐2‐hydroxypropylcitrate, starch‐2‐hydroxypropylphosphate and starch‐2‐hydroxypropylsulfate, were prepared and evaluated as flocculants. The flocculation efficiency was monitored via estimation of the optimal dose, transmission % and weight removal %. The different factors affecting the flocculation were studied. These factors include the type of acidic group, the length of the chain bearing the acidic group, the chemical formula and molar mass of the flocculant, the acid content and the pH. The flocculation efficiency of various anionic starches depends on (a) the acidic group type and follows the order: sulfate > phosphate > carboxyl; (b) the length of the alkyl chain bearing the carboxyl group in the order: starch‐2‐hydroxypropylcitrate > carboxyethyl starch > carboxymethyl starch; (c) the chemical formula which indicate that the flocculants prepared via grafting have a higher flocculation efficiency than those prepared by etherification. The flocculation efficiency increases with increasing the acid content and/or decreasing the molar mass of the flocculant. Flocculation efficiency at pH 8 is higher than tat pH 6.
Six types of cationic starch derivatives bearing different types of amino groups, i.e., primary, secondary and tertiary or quaternary ammonium salt, were prepared and evaluated as flocculants. Native and hydrolyzed maize starches were used as parent materials for these derivatives. The different factors affecting flocculation were studied. These factors include (a) flocculant dose, (b) pH of the flocculation medium, (c) chemical formula of the flocculant and (d) type of cationic starch, its molecular weight and nitrogen content.
Grafting of methacrylic acid (MAA) on starch, poly(vinyl alcohol) (PVA), and a mixture of starch and PVA, using a potassium persulfate/ sodium thiosulfate redox initiation system was carried out. Polymerization was studied with respect to graft yield, homopolymer formation and total conversion. These polymerization criteria were found to depend largely on the concentration of both MAA and initiators, duration and method of polymerization.The results reveal a number of interesting points which reflect the impact of the condition of the treatment. The main product of the polymerization reaction [poly(MAA)starch/PVA graft copolymer] was formed and precipitated during polymerization and can be easily separated by filtration as pure product.Application of these copolymers to cotton fabric was also carried out to evaluate the suitability of such modified products as sizing agents.
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