Preparation And Properties Of Unsaturated Polyester-Isocyanate Block Copolymer And Its Glass Fiber Reinforced Plastics (GFRP)

In the basis of molecular design, this work develops a kind of new modified unsaturated polyester with excellent properties, such as high modulus, high strength, low shrinkage and rapid infiltration.General purpose unsaturated polyester resin is a relatively low-end thermosetting resin product, it has some shortcomings, such as large shrinkage, poor alkali resistance, poor infiltration and brittleness after curing, which limit the application of UP.To reduce the brittleness of UP, we increased the amount of diethylene glycol and decreased the amount of propylene glycol. With the increase of diethylene glycol, the mobility of molecular chain becomes easier, so the flexible of the resin becomes better. when the molar ratio of propylene glycol to diethylene glycol is 1:1, the impact strength of UP is greatly improved; To improve the strength, modulus, adhesion to glass fiber and decrease shrinkage, we use isocyanate(TDI) to modify the unsaturated polyester, as a result we introduced a large number of urethane groups and the benzene rings to the molecular chain of unsaturated polyester. The presence of urethane groups can improve the polarity of molecular chain and enhanced the interaction between the chains, as well as improving the strength of the resin. It can form hydrogen bonds between urethane and the hydroxyl on the surface of glass fiber, which would enhance infiltration of resin and improve the strength of fiber reinforced composites. The introduction of the benzene rings can improve the rigidity, modulus and hardness of the resin, when the concentration of TDI is up to 9% the strength of modified resin is relatively high.Through molecular structure design, we synthesized a hydroxyl-terminated unsaturated polyester oligomer first, then we cap one part hydroxyl of the oligomer, at last we introduced TDI to react with the capping oligomer. Through the block copolymerization of TDI, carbamate groups were introduced to the molecular chain of unsaturated polyester, we synthesized a new kind of unsaturated polyester which was modified by block copolymerization of polyurethane. In the reaction process we can use titration and Fourier transform infrared spectroscopy to judge the extent of reaction and the reaction end point.The results showed that, after modification, the tensile strength of the resin was 79MPa and the bending strength could be up to 140MPa. According to the contact angle measurement and scanning electron microscopy, we proved that the adhesion between resin and fiber significantly improved. When made into glass fiber composite, the tensile strength is 1050MPa and the flexural strength can be up to 1220MPa, these result were better than that of the general purpose 196's glass fiber composite.