Synthesis Of Novel Styrene-free Unsaturated Polyester Coatings

Unsaturated polyester coatings have high hardness, high gloss, fullness, good chemical resistance and other excellent comprehensive performances. It has a low cost and is easy to be processed. So it is widely used on the surfaces of furnitures, musical instruments and other wood carpentry. Its drawback is that the traditional unsaturated polyester coatings use styrene as active monomer that is volatile and toxic. In order to solve this problem, this study aims to develop novel styrene-free unsaturated polyester coating.Firstly, low viscosity unsaturated polyester oligomer was synthesized. When the mole ratio of binary acid and dibasic alcohol was 1.3, the molar ratio of maleic anhydride and phthalic anhydride was 8/2, the molar ratio of triethylene glycol and glycol was 2/8 and the polymerization inhibitor content was 0.74 wt %, the viscosity of the unsaturated polyester oligomer came to the lowest, nearly 14500 cp. Then hyperbranched unsaturated resin and multi-allyl urethane oligomer were used as the crosslinking agent of the unsaturated polyester oligomer respectively. The performance of two kinds of coatings was compared. The result showed that the unsaturated polyester coating crosslinked by the hyperbranched unsaturated resin had a better film performance. The bending flexibility and impact resistance of the films were improved. The films became strong and tough. When hyperbranched unsaturated resin content was 30wt%, the comprehensive performance was the best, with which the surface drying time was 40 min, the pencil hardness was 2H, the glossy was 88, the bending flexibility was 3 mm, the impact strength was 45 cm, the tensile strength of 10.15 MPa, the elongation at break 13.61% and the heat resistance was excellent. So the comprehensive performance was improved greatly.The curing process of the low volatile unsaturated polyester coatings curing process were studied with the viscosity, gel ratio, conversion ratio, volatile component content and some other characteristics. The non-isothermal DSC method was used to study the curing kinetics of unsaturated polyester coating. The apparent activation energy of curing reaction was 41.67 k J?mol-1, the reaction series was 0.962 and the curing system dynamics equation was dα/dt=1.119?106?exp(-5.013?103/T) ?(1-α)0.962. The apparent activation energy was low which indicated that the curing activity of the unsaturated polyester was high, the energy barrier of the curing reactions was low. The curing process of the unsaturated polyester coating was studied for a better application of this novel styrene-free coating.The synthesized styrene-free unsaturated polyester coating fundamentally decreased the emission. It can be applied to the surface of the wood furniture with excellent performance.