Preparation And Study Of Structure And Properties On Polyurethane Elastomers With Long Pendant Chains

As the development of the society, it needs more effective control of vibration and noise,and using the damping materials is the effective measure to reduce the vibration and noise.Polyurethane elastomer is a kind of widely used damping material, because its molecular structure can be designed flexibly. High damping property materials require that the damping factor(tanδ) is greater than 0.3 for a temperature range of at least 60℃. The effective damping temperature range of simple homogeneous component polyurethane elastomers is less than 40℃,which can not meet the requirements of the high damping material.In the paper,beginning with the structure design of the molecular network, the long pendant chains ware linked into the polyurethane network structure. We focused on raising the whole “damping platform” of polyurethane elastomers after Tg, in order to obtain high damping polyurethane elastomer material witch damping performance is less dependent on temperature.In this paper, we used a new modified method which is linking the long pendant chains into the polyurethane network structure. Single functional group methoxypolyethylene glycols as the long pendant chains, TDI based polyurethane elastomers with long pendant chains were synthesized. The effects of long pendant chains on damping properties, micro phase separation and hydrogen bond were focused on. Dynamic mechanical analysis(DMA)showed that with the increase of long pendant chains contents, the “damping platform” after Tg was significantly improved. Atomic force microscopy(AFM) analysis showed that the introduction of the long pendant chains can reduce the degree of micro phase separation of soft and hard segments. Fourier transform infrared spectroscopy(FTIR) showed that more long pendant chains made hydrogen bond stronger. In addition, the effects of different R values, soft segment structure, soft segment molecular weight and removal of free molecules on the structure and properties of TDI based polyurethane elastomers with long pendant chains were also studied. The results of the study showed that: when long pendant chains content(Wpen) was 60%, and the R value was 1.3, the TDI based polyurethane elastomers made form polyester type soft segment with molecular weight of 2000 have a wide and flat damping platform which tanδ is about 0.5. And the polyurethane elastomers exhibit high damping properties(tanδ≥0.3)with a broad temperature range about 190℃ from-60℃ to130℃ and a wide frequency range 10-2Hz to 108 Hz, and exist 70% repair rate.The introduction of long pendant chains to Pu elastomers network is an effective way to improve“damping platform”.In order to improve the mechanical properties of high damping polyurethane, MDI based polyurethane elastomers with long pendant chains were prepared, by using symmetrical molecular structure MDI instead of TDI. The effects of long pendant chains contents, different soft segments and R values, and crystallization degree on structure, damping properties,and mechanical properties of MDI based polyurethane elastomers with long pendant chains were also studied. DSC analysis showed that: long pendant chain contents is higher and the R value is greater, the greater the degree of crystallization; polyurethane can have a crystallization phenomenon when Wpen increased to at least 50% and the R value reached at leas1.3. The tensile strength of MDI based polyurethane elastomers with long pendant chains was more than 6.5Mpa,at the same time the damping property was excellent. The method of molecular structure design that introduction of the long pendant chains into polyurethane with more regular hard segment structure, can achieve a relative balance of the damping capacity and mechanical properties.