Synthesis and properties of UV-curable hyperbranched polyester

Using the molten polycondensation, the second to fourth generation of hyperbranched polyesters with a great number of hydroxyl groups were synthesized and characterized based on the pentaerythritol as core and 2, 2-bis(hydroxymethyl) propionic acid as arm. They had high branched degrees, low viscosity and good thermal stability. By methacryloyl anhydride, the hyperbranched polyesters were modified to be the hyperbranched methacrylates with C=C at the chain ends. The percent conversion could be reached above 89% under the optimum reaction conditions. The modified hyperbranched polyesters exhibited lower viscosity, two segmental thermogravimetric curve and lower glass transition temperature (T_g). When the hyperbranched methacrylates with low viscosity were applied in UV-curable coating for metals, it could take less solvent, fast coating speed and complete curing. The effects which the hyperbranched polyesters with different C=C contents took on the properties of UV-curable coating such as gel content, adhesive strength, impact strength, flexibility, hardness and the solvent resistances were studied. With the improvement of C=C contents, the gel contents were increased. Also the mechanical properties and solvent resistances of coatings were changed significantly. The experiments exhibited that it would help to gain the perfect UV-curable materials by choosing the hyperbranched polyesters with different contents of active groups.