Relationship between starch liquefaction behavior and properties of polymer coated urea from liquefied starch

摘要

The relationship between starch liquefaction behavior and properties of coated urea was explored to give some insights into the optimized technical selection of bio-polyol for polymer coated urea. The liquefied corn starch was monitored for insoluble residue content, viscosity, acid value and hydroxyl value. Nitrogen release, water permeability and biodegradation properties of coating material were also studied. FTIR and 1H-NMR results revealed that alcoholysis, hydroxyalkylation and side reactions co-existed during the liquefaction process, and side reactions predominated as the process continued. It was found that re-condensation leading to the increase of polyester polyols was beneficial for subsequent coating of urea according to the nitrogen release and biodegradation performance. The selected bio-polyols derived from starch can be available to prepare polymer coated urea being more accordant with the nutrient requirement of plants at growth stages.