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Characterization of the Reaction Products for Starch and Acrylonitrile
Author(s) -
Hebeish A.,
Khalil M. I.
Publication year - 1988
Publication title -
starch ‐ stärke
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.62
H-Index - 82
eISSN - 1521-379X
pISSN - 0038-9056
DOI - 10.1002/star.19880400306
Subject(s) - acrylonitrile , starch , sodium hydroxide , chemistry , sodium , polymer chemistry , modified starch , nuclear chemistry , organic chemistry , copolymer , polymer
Rice starch was reacted with acrylonitrile in presence of sodium hydroxide under different conditions including liquor/starch ratio, sodium hydroxide concentration and acrylonitrile concentration as well as reaction time and temperature. The reaction products were analyzed for nitrogen and carboxylic contents and the results obtained were used for calculation of the degree of substitution (D. S.), reaction efficiency (R. E.) and total extent of etherification. Reaction products refered to mixed starch ethers, namely, cyanoethyl starch, carbamoyl ethyl starch, and carboxyethyl starch. Due to analytical difficulties to differentiate between the first two ethers, they were looked upon as cyanoethyl starch. The D. S. of the latter and the R. E. of cyanoethylation were greatly favoured at temperature not exceeding 40°C using lower liquor ratios for reaction time up to 4h provided that certain acrylonitrile and sodium hydroxide concentrations were used. Specifiably, the most appropriate conditions for preparation of cyanoethyl starch comprized:starch/acrylonitrile ratio 1 : 1, liquor/starch ratio 1:7.5 and sodium hydroxide 0.5N at 40°C for 4 h. Under these conditions a D. S. of 1.2 and R. E. of 40% could be achieved. Higher temperatures, i. e. 50 and 60°C, acted in favour of carboxyethyl starch formation particularly when the reaction was allowed to proceed for more than 3 h at 50°C and 0.5 h at 60°C.