Properties Research On Preparation Of PU Prepolymer Modified UPR And Its Composites

Unsaturated polyester resin is one of three thermosetting resin matrixes, due to low prices, good mechanical properties, cost-effective, it widely used in fiber reinforced plastics in this area. However, with the development of composite materials industry, the request of unsaturated polyester resins are increasingly high, unsaturated polyester resin also shows some shortcomings, such as large shrinkage, brittleness after curing.In this paper, polyurethane composites were studied. First, through the-NCO content and infrared analysis, I studied the synthesis of polyurethane prepolymer to select the best synthesis conditions. And then I successfully synthesized 8 kinds polyurethane prepolymers under optimal conditions, and PU prepolymers was added into unsaturated polyester resins respectively according to-NCO:-OH equivalent ratio, static mechanical properties of modified resin system were studied. In addition, I've also choosing scanning electron microscopy and DMA as supporting analytical method to study the trends of properties. After determining the best mechanical properties of modified system, I've prepared resin matrix composite materials with the best mechanical properties of the modified prepared to study the mechanical and interface properties of the composite.In research of-NCO groups terminated polyurethane prepolymer synthesis, TDI: PEG mole ratio is 4 and 3, prepolymer itself has a small viscosity, and if TDI:PEG mole is 2, the viscosity was more than 6000mPa·s. TDI:PEG mole ratio is bigger, PEG molecular weight is smaller, the stability of prepolymer is getting worse. At 80℃,3 hours of synthesis conditions, TDI could completely reacted with PEG.In the research of PU prepolymer modified-OH groups terminated unsaturated polyester resin, results showed that after adding it polyurethane prepolymer into unsaturated polyester resin, the terminal-NCO groups have reacted with hydroxyl completely to form cross-linking. After adding PU prepolymer into UPR, impact, bending and tensile properties increased, when PEG600 and TDI:PEG mole ratio was 2, prepolymer had increased impact property the most, the maximum 68kJ/m2, which is ten times bigger than UPR. When molecular weight was bigger, TDI:PEG mole ratio closer to two, modified UPR showed greater impact strength, lower bending strength and modulus. When PEG400 and TDI:PEG mole ratio of the prepolymer is three,-NCO:-OH equivalent ratio of 1.5 by adding the amount added to the hydroxyl-terminated unsaturated polyester resin, the composites has the best mechanical properties, impact property was 3 times than before, bending strength was one and a half times, tensile strength was 1.7 times and elongation at break was two times than before.Finally, this paper also researched the mechanical and interface properties of modified UPR composites. Results showed that compared to the unmodified hydroxyl terminated unsaturated polyester resins and vinyl resins, after modifying, the mechanical had been significantly enhanced, the bending strength increased by 79%, tensile strength increased by 18% and elongation at break was increased by 16%, flexural modulus and tensile modulus were also improved to some extent. At the same time, tensile cross-section SEM morphology analysis showed that the resin matrix and glass fibers have a good interface, glass fiber attached to the resin matrix and more infiltration of resin and fiber is good.