Preparation and properties of star-shaped UV-curable polyester methacrylate resins with Low viscosity derived from renewable resources

Abstract

To meet the growing needs of environmental protection and green sustainable development, we have synthesized a series of low viscosity and colorless transparent UV-curable polyester methacrylate resins derived from renewable biologically fermented lactic acid (LA). The structure and properties of these polyester methacrylates were characterized by 1H-NMR, FTIR, and viscometer. The results show that the viscosity of polyester methacrylates can be dramatically reduced from 34,620 mPa·s of PLA-DA to 160–756 mPa s of 4sPCLA-TA by random copolymerization of LA and ε-caprolactone (CL) and further introducing star-shaped structure into the oligomer chain. UV-curing kinetic studies demonstrated that lowering resin viscosity positively affects the polymerization of double-bonds. The changing gel contents agree with these observations. The polyester-based methacrylic resins were used to prepare UV-cured coatings, and the performance of the coatings was tested systematically. The 4sPCLA-TA resin with 756 mPa·s viscosity can still exhibit a high tensile strength of 59.2 MPa, bending strength of 92.3 MPa, and bending modulus 2.96 GPa, the glass transition temperature of 154.8 °C. UV-cured coating of the 4sPCLA-TA has a high pencil hardness of 4H and Shore D hardness of 77.6, adhesion of 2 grade, and 3 mm flexibility. Overall, renewable polyester-based methacrylic resins developed in this work are excellent candidates for preparing environmentally friendly UV coatings.