Research On Stable Damping Polyurethane Materials In A Wide Temperature Range

In order to solve the fatigue failures caused by vibration for aerospacecraft in some extreme temperature environments,damping materials with a wide temperature range are required.The damping material based on polyurethane,as a kind of functional material that can absorbs vibration energy by viscoelasticity of polymer and convert vibration energy into heat energy dissipation,has good processing technology,excellent damping performance and good resistance to high and low temperature.This project aims to develop polyurethane based damping material that can satisfy a wide temperature range(-50 to 100?),and the damping factor remains relatively stable in the environment of space cabin.Three kinds of chain extenders with long-chain structure were synthesized by the special design of the polymer structure and were introduced in the polyurethane chains.The damping properties was researched by varying many influence factors,such as molecular weight of soft segment,crosslink density,structure of chain extender,content of mica and test frequency.The synthesized polyurethanes were modified by blend with two kinds of epoxy resins and the damping capacity and heat resistance of the blending materials were studied.Firstly,the NCO-terminated 210 polyurethane prepolymer,NCO-terminated 220 polyurethane prepolymer and NCO-terminated 330 polyurethane prepolymer were synthesized.The prepolymers were extended and crosslinked by TMP and BD-1.The 210 BD-1 polyurethane,220 BD-1 polyurethane and 330 BD-1 polyurethane were prepared,and their damping properties were tested.The results show that the damping peak of 210 BD-1 polyurethane is higher than that of 220 BD-1 polyurethane.The change of crosslink density has little effect on the damping temperature range of the two kinds of polyurethane,but the maximal loss factor increases.The maximum loss factor of the two kinds of polyurethanes decreases with the addition of flake mica.The damping temperature range of 330 BD-1 polyurethane is obviously higher than that of the former.The effective damping temperature range increases by 29.2? with the decrease of the crosslink density.The effective damping temperature range increases by 7.7°C after adding 20 portions of flake mica.Finally,the effective damping temperature range of 330 BD-1 polyurethane is-50~64.2?,and the elongation at break is 361 %.Secondly,in order to improve the damping property of 210 polyurethane and 220 polyurethane,three kinds of chain extenders,AD-1 containing benzene ring and flexible chain structure,AD-2 containing a flexible chain structure and BD-2 containing much sterically hindered benzene ring structures with long-chain structure were synthesized.The damping temperature range is widened by increasing the friction loss between the polyurethane backbone and side chain with rigid benzene ring and flexible long-chain structure.The results show that the damping factor of 220 polyurethane with longer flexible chain can avoid the damping peak at room temperature and remain stable.By comparing the influence of crosslink density on the damping factor of the polyurethanes,it is found that the effective damping temperature range of the three kinds of polyurethane is widened with the decrease of 3OH/2NH ratio.When the 3OH/2NH ratio is 0/1,the highest effective damping temperature of 220 AD-1 polyurethane reaches 100°C,and it is 87.4°C and 78.2°C for 220 AD-2 and 220 BD-2 polyurethane,respectively.By comparing the effects of structure of chain extender on the polyurethane damping factor,it is found that the effective damping temperature range of 220 BD-2 polyurethane is widest when the 3OH/2NH ratio is 0.25.By comparing the effect of mica content on the polyurethane damping factor,it is found that the 220 AD-1 polyurethane has the best damping property when 20 portions of mica is added,and the damping temperature range increases by 52°C.The 220 AD-2 polyurethane has the best damping property when 25 portions of mica is added,and the damping temperature range increases by 30.4°C.Comparing the effect of test frequency on the damping factor of polyurethane,the results show that the effective damping temperature range of the two kinds of polyurethane increases first and then decreases with the increase of test frequency,and damping temperature range of 220 AD-1 polyurethane and 220 AD-2 polyurethane are the widest when the test frequency is 50 Hz,and the effective damping temperature is 115.4°C and 97.8°C,respectively.Finally,the 220 AD-1 polyurethane,220 AD-2 polyurethane,220 BD-1 polyurethane,220 BD-2 polyurethane synthesized in the previous two chapters were blended with the two kinds of epoxy resins(Bisphenol F epoxy resin,PBA/E-51 epoxy resin),respectively.Then eight kinds of polyurethane/epoxy composite damping materials are obtained.By changing the contents of each epoxy resin,the damping properties of them were researched.By comparing the damping properties of four kinds of polyurethanes blended with epoxy resin,it is found that the damping property of 220 BD-2 polyurethane/epoxy is superior.When the amount of epoxy is appropriate,the blend of 220 BD-2 polyurethane and epoxy shows two damping peaks,the morphological structure of the blend exhibits a microscopic phase separation.The damping temperature range of the composite material is obviously widened.Especially,the addition of EP-2 has the significant effect.When 20 portions of PBA/ E-51 epoxy resin is added,the effective damping temperature range is the widest,which is from-50? to 115°C.