Abstract: The tricarboxylic castor oil containing carbon-carbon double bond（MACO） produced from maleic anhydride and castor oil is used as internal crosslinking agent to prepare the MACO modified waterborne polyurethane emulsion MACO-WPU. The structure of modified polyurethane is characterized by FT-IR. It is confirmed that MACO is successfully introduced into polyurethane molecular chain. The effects of MACO content on the properties of polyurethane emulsion and film thereof are studied by means of the mechanical properties， water absorption， particle size and thermogravimetric analysis. The experimental results show that the emulsion has good appearance and stability when the mass ratio of MACO is 3％. Meanwhile， the average particle size was 48.45 nm. The tensile strength and elongation at break of the film are severally 13.15 MPa and 195％， and the thermal stability of WPU is slightly improved as compared with the unmodified WPU.
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