Starch-g-poly(vinyl alcohol) as a new material for encapsulating agrochemic
al for slow release has been studied. By encapsulating 2,4,5-T (2.4.5-trich
lorophenoxyacetic acid) as model herbicide within polyvinyl alcohol-grafted
starch matrix, the effects of the graft modification on the matrix behavio
rs and release rate of the herbicide were evaluated. The polyvinyl alcohol
branches attached onto starch enhance the association of the grafted starch
macromolecules, which make the matrix show a tightening effect. Therefore,
the swellability of the matrix is decreased and the rate of the herbicide
released from the matrix in wet environments can be reduced. Increasing the
grafting ratio is Favorable to the slow release, Moreover, the influences
of the mole ratio of sodium hydroxide to acetate, herbicide content, and pa
rticle size upon the matrix behaviors and release rate were also investigat
ed. The grafted starch is especially suitable for encapsulating the alkali-
sensitive chemicals such as carboxylic-containing herbicides because the cr
oss-linking procedure under alkali condition in encapsulation is avoided. (
C) 2001 Elsevier Science Ltd. All rights reserved.