Graft copolymerization of methacrylic acid (MAA) onto starch using a potassium persulfate/sodium thiosulfate redox initiation system was investigated. Emphasis was placed on the promotion of graft formation while minimizing homopolymerization. This could be achieved through a thorough investigation into the major factors affecting the polymerization reaction such as the state of the starch, redox ratio of the initiator, monomer and initiator concentrations, time and temperature of polymerization, and material-to-liquor ratio. The results obtained imply that the magnitude of the polymer yield including total conversion, graft yield, and homopolymer are determined by these factors. The yield is favored under the influence of higher temperature, longer time, short liquor, and increased monomer and initiator concentrations. A poly-(MAA) -starch graft copolymer is the main product of the polymerization reactions only when starch was preswelled (through cooking prior to grafting). Moreover, this grafted product could be precipitated by more dilution with water and easily separated by filtration. Hence, the results of the current work formed the basis of a novel method for the synthesis of poly(MAA) -starch graft copolymers. The mechanisms involved in the synthesis are reported.

Graft polymerization of maize starch with acrylic acid using potassium persulphate as free radical initiator was investigated under different conditions. Variables studied included initiator concentration, acrylic acid concentration, starch/water ratio and polymerization temperature. The carboxyl content of the grafted starch was determined and used for calculation of the grafted yield. It was found that the graft yield increases by increasing persulphate; no significant enhancement in grafting could be observed upon using higher persulphate concentrations. Grafting increases also by increasing acrylic acid concentration up to 150% (based on wt. of starch) and tends to decrease at higher concentrations. Starch/water ratio of 1:6 constitutes the optimal for maximum grafting. Raising the polymerization temperature from 25 to 43°C enhances the polymerization rate. The apparent activation energy of the copolymerization reaction amounts to 182.17 Joule/mole.

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Reaction of starch with acrylamide was carried out under different conditions including reaction medium, catalyst, acrylamide concentration, reaction time and temperature as well as liquor ratio. Organic solvents, namely, isopropyl alcohol, dimethylformamide and cyclohexane alone and in admixture with water at different ratios were used as reaction medium. Catalysts used include sodium hydroxide, trisodium phosphate, sodium carbonate, sodium benzoate, sodium acetate and sodium formate. Acrylamide concentration ranged from 25% to 200%, based on weight of starch. The reaction was studied over a wide range of temperature and duration. Results obtained showed that the extent of reaction of starch with acrylamide is governed by each of these factors. Furthermore, this reaction yields mixed starch ethers, namely carbamoylethyl starch and carboxyethyl starch. Solubility, viscosity and moisture content of these starch ethers are determined by the sum of the amide and carboxyl contents.

SynopsisGraft polymerization of acrylic acidhtyrene mixtures on poly(ethy1ene terephthalate) fibers using HzOz as initiator was investigated under different conditions including acrylic acidhtyrene ratio, monomer mixtures concentration, initiator concentration, polymerization temperature, pH of polymerization medium, addition of metallic salts, and use of solvent/water mixture instead of aqueous medium. It was found that the rate and extent of grafting for acrylic acidhtyrene mixtures were much higher than those of single monomers, indicating a synergestic effect. Maximum percent grafting occurred when acrylic acidhtyrene mixture at a ratio of 30:70 was used. Increasing the monomer mixture concentration from 2% to 40% was accompanied by a significant enhancement in percent grafting. The latter increased also significantly as the H202 concentration increased from 10 to 150 meqb, a further increase in HzOz concentration decreased grafting. No grafting took place at 65OC even after 4 h. Raising the polymerization temperature to 75°C expedited grafting; the magnitude of the latter increased by increasing the temperature up to 95OC. Addition of copper sulphate and ferrous ammonium sulphate to the polymerization system offset grafting, the opposite holds true for lithium chloride provided that its concentration does not exceed 15 mmoleb. Methyl alcohol/water mixture (2080) constituted the optimal medium for polymerization. Grafting of acrylic acidhtyrene mixtures to poly(ethy1ene terephthalate) fibers resulted in considerable improvement in moisture regain of the latter.