The Synthesis And Application For Unsaturated Polyester Polyurethane Block Copolymer

Unsaturated polyester resin (UPR) is one of important thermosettingresins. It is widely used in industry, agriculture , national defense andconstruction industry due to its excellent physical and mechanicalperformance, low price and cost-effective. As the Unsaturated polyesterresin industry developed, its shortcomings are gradually appearing in someparts, such as high curing brittleness and high shrinkage rate, etc.Polyurethane has excellent flexibility and impact resistance. By addingblend of elastomeric polyurethane, the brittleness of UPR can be effectivelyimproved and its shrinkage rate is dropped. However, unsaturatedpolyester's high crystalline resulting in poor compatibility withpolyurethane. The capacity of polyurethane is limited in the mixedcomposition. Although the toughness of unsaturated polyester is improvedand its shrinkage rate is dropped, other mechanical properties of thematerial significantly reduced.In this paper, the synthesis and application of the unsaturated polyesterpolyurethane block copolymer were studied. Solventless air-curingunsaturated polyester polyurethane coating was synthesized by the methodof molecular design. Hydroxyl-terminated unsaturated polyester oligomerof different number of double bonds was first obtained by the phasepolycondensation of unsaturated binary acid, saturated dicarboxylic acidand glycol. Then unsaturated polyester polyurethane prepolymer wassynthesized by the addition polymerization of hydroxyl-terminatedunsaturated polyester oligomer, polyethylene glycol and Toluene discarnate(TDI).Then the unsaturated polyester polyurethane block copolymer resinwas synthesized after the prepolymer was stopped end by hydroxyl ethylmethacrylate. Solvent-less air-curing unsaturated polyester polyurethanecoating was prepared with the styrene as reactive diluents, methyl keteneperoxide as initiator. The optimum synthesis conditions of Unsaturatedpolyester polyurethane were :the start synthetic temperature was 150℃,average number of double bonds was 3.3;The optimum synthesis conditionsof Unsaturated polyester polyurethane block copolymer were:TDI contentwas 11%, PEG-400 content was 15%;The optimum synthesis conditions ofsolventless air-curing unsaturated polyester polyurethane coating were: reactive diluents was 35%～40%, initiator was 1.0%, accelerant was 0.2%.The mechanical properties of solventless air-curing unsaturated polyesterpolyurethane coating were: the hardness was 6H, the impact strength was 50cm, the bending strength was 2mm and the adhesion strength was level 1.In the study of unsaturated polyester polyurethane block copolymercomposite materials, the effects of structure of unsaturated polyesterpolyurethane block copolymer on the tensile strength, bending strength,impact strength and curing shrinkage rate of the modified resin system werestudied with the IR,SEM and DSC as auxiliary analysis .And the optimalmechanical properties of the modified system were decided. The results ofthe experiment indicated that the mechanical properties of the modifiedsystem improved(impact strength increased 57%, curing shrinkage ratedeclined 67% and both tensile strength and bending strength increased morethan 2 times) because of the copolymerization of polyurethane andhydroxyl-terminated unsaturated polyester, when the average number ofdouble bonds of hydroxyl-terminated unsaturated polyester was 3.3, the molratio of -OH and -NCO was 1:1.50 and PEG-400 content was 15%. And theproperties of the composite materials prepared by resin matrix of theoptimal mechanical properties and glass fiber were optimal. The impactstrength(55.267/KJ/m 2 ) was 5 times than the unsaturated polyester resin,the bending strength(78MP) was 3 times and the tensile strength(84MP) was4 times, the curing shrinkage rate(<1) decreased 89%.In the end of the paper, we analyzed the micromor-phologies oftensile fracture-surface of resin system and composite materials. We foundthat the micromor phologies of the modified resin which had crackrefinement was better than the nonmodified resin. And from the analysis ofthe micromor-phologies of the composite materials with tensile fracture, wefound that the surface of glass fiber had more resin matrixes. This indicatedthat there was a bonding interface between the modified unsaturatedpolyester polyurethane and the glass fiber.