Effect of structure on the properties of ambient-cured coating films prepared via a Michael addition reaction based on an acetoacetate-modified castor oil prepared by thiol-ene coupling

The Michael addition reaction was used to create ambient curable film materials based on an acetoacetate-modified castor oil, and a multifunctional alamine was prepared. The thiol-ene coupling reaction could change the proportion of hydroxyl groups in the castor oil, thereby improving the crosslinking density and mechanical properties of the coating films. The acetoacetate-modified castor oil was achieved in two steps. First, the C=C bonds of castor oil were coupled using a thiol-ene coupling reaction, which has a high conversion rate and few by-products. Second, acetoacetate-modified castor oil was prepared by a transesterification reaction between tert-butyl acetoacetate and modified castor oil. The acetoacetate-modified castor oil was characterized by Nuclear magnetic resonance (NMR), Fourier Transform infrared spectroscopy (FTIR), Gel Permeation Chromatography (GPC) and viscosity measurements. Finally, coating films were prepared from the acetoacetate-modified castor oil and 4,4-diaminecyclohexylmethane via a Michael addition reaction at room temperature (25 degrees C). The mechanical properties were noticeably improved compared to those of the unmodified castor oil film. The tensile properties increased from 0.68 MPa to 1.76 MPa, and the glass transition temperature (T-g) increased by approximately 30 degrees C.