| Polyaspartic acid is a kind of biodegradable environmentally friendly scale inhibitor. For its not perfect dispersant ability, the use of the inhibitor is confined. Based on the study of polyaspartic acid , its graft copolymers were synthesized by introducing other function groups such as hydroxyl and sulfo.In this paper, polysuccinimide was synthesized by pyrocondensation polymerization of L-aspartic acid monomer. The effect of reaction time on the molecular weight and the molecular weight on scale inhibition performance were studied. It showed that the optimal conditions are as follows: reaction temperature at 240℃, reaction time at 4 hours and the molecular weight of 3200.Polysuccinimide, 2-aminoethanesulfonic acid and 2-aminoethanol were used to synthesize polyaspartic acid graft copolymers. The performance of the graft copolymers were studied by static scale inhibition test ,rotation specimen method and shaking-bottle incubating test. The results show that polyaspartic acid graft copolymers are biodegradable environmentally friendly scale and corrosion inhibitors. They have outstanding performance of scale inhibition on calcium phosphate and dispersing ferric oxide. Scale inhibition rate of polyaspartic acid graft copolymer containing hydroxyl on calcium phosphate is 98.2% with a dosage of 8mg/L and the mole ratio of hydroxyl and polysuccinimide 0.8. While the scale inhibition rate of polyaspartic acid is only 1.5%. When the mole ratio of sulfo and polysuccinimide is 0.2, the performance of dispersing ferric oxide of the agent is the best. The lest diaphaneity of the agent is 33.2% with a dosage of 15mg/L. The lest diaphaneity of polyaspartic acid is 89.7% with a dosage of 15mg/L.The influence of polyaspartic acid and its graft copolymers on calcium carbonate crystal and the scale inhibition mechanism were studied. It showed that calcium carbonate crystal were split and distorted obviously by polyaspartic acid graft copolymers. Calcium carbonate crystal was more dispersive.
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