ABSTRACT
Polyurethane composite coatings on urea granules were prepared by SBA-15 mesoporous silica (in as-synthesized and calcined forms) as a pseudo-crosslinker without any other chain extenders. The calcination of mesoporous silica leaded to reduction of hydroxyl groups and increase of mesopores. The composite coating containing calcined SBA-15 showed enhanced controlled release properties compared with the other two coatings. At the loading content of 1 wt%, the initial release rate and release duration of urea coated by polyurethane/calcined SBA-15 composite were 0.08% and 83 d, respectively. It is shown that the calcination played an important role in controlling the properties of composite coating.
GRAPHICAL ABSTRACT
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Acknowledgments
The authors are grateful for financial support from National Key Research and Development Program of China (2017YFD0200705, 2017YFD0800604) and National Science Foundation of China (31301846, 31301847).