Synthesis And Properties Of UV-resistant Polyester Resin

As one of important branches of powder coatings, polyester powder coatings which have relatively lower cost, excellent weather resistance and superior overall performance, are widely used in air conditioner external unit, outdoor architecture, agricultural equipment, traffic facilities, and other outdoor areas. But under the irradiation of ultraviolet light, photo-oxidation degradation always occurs in outdoor polyester products during their service, which greatly reduces their durability. In order to improve the UV weather resistance of polyester powder coating and to extend their service time, the major research works of this article were as the following:(1) The synthesis of UV resistant polyester. Isophthalic acid and neopentyl glycol were chosen as the essential monomers, which having good weather resistance and relatively lower price, to synthesize UV-stable polyester resins by melt polymerization. The characterization results of DSC、GPC、TG、UV-Vis showed that the polyester product has high Tg and low acid value. Compared with the commercially available weather-resistant polyester, it has moderate molecular weight, narrower molecular weight distribution, better thermal stability and better UV stability.(2) The in-situ modification of polyester.To obtain a uniform modified polyester system,polyester resin was modified via in-situ polymerization with rutile nano-titanium dioxide which was surface-modified with KH560. Then the product was repeatedly dissolved and washed with THF.XPS elemental analysis showed that the C/O of the residual product was 40.28/41.52, and TG thermal analysis showed that its mass change was 8.96%,which proved the existence of chemical bonding between the modified TiO2 with polyester matrix. UV-Vis spectra and outdoor weathering test showed that the UV stability of polyester modified with TiO2 via in-situ polymerization was significantly improved.(3) The modification of polyester with additives. First,TiO2 with epoxy reactive group and UV absorbers UV-0 were melt blended to obtain the organic/inorganic hybrid-blending UV stabilizer. Then the UV stabilizer was added into polyester resin by melt extrusion. After melt blending reaction, the color of the product turned yellow, the C/O of the residual product increased and the ultraviolet absorption ability improved, which indicated that the reaction between TiO2 and UV-0 is chemical-graft-blending. UV-Vis spectra and outdoor weathering test showed that the UV stability of polyester modified by hybrid-blending UV stabilizer was further improved.