Research On Synthesis Of Polyurethane Matrix Constrained Damping Composites And Their Properties

With the development of aviation, aerospace, marine, transportation and heavymachinery, the polymer-based damping materials, because of the nature of deformation energy,is widely used to control the vibration, noise and fatigue failure induced by mechanicalvibration. However, general polymers usually have narrow glass transition region and lowmodulus, which can limit their applications to some extent. In order to obtain good dampingmaterials with broad temperature range, excellent damping property and high modulus,several sections are mainly included in this dissertation just as follows:In this paper, the branched polyurethane composites and epoxy resin were prepared Thereaction mechanism was characterized by FT-IR spectra, and the microstructure wascharacterized by SEM and XRD. The macroscopical performances were characterized bydynamic mechanics analysis(DMA), the electronic universal testing machine, and cantileverbeam impact tester.Firstly, the branched polyurethane elastomer was prepared, and the optimum ratio wasobtained. The main chain type prepolymer was synthesized with PPG-1000, PPG-2000as softsegment and TDI as hard segment, and the–NCO content was around6.0%. The branch chaintype prepolymer was synthesized by PPG-2000and TDI, and the–NCO content was around2.5%. TMP was applied as cross-linking agent. Then, the main chain type prepolymer, thebranch chain type prepolymer and TMP were well-mixed and cured at100℃. The branchedpolyurethane elastomer was investigated by DSC, DMA, electronic universal testing machine.The results showed that hard domain and soft domain of the branch chain type polyurethaneelastomer possessed good compatibility, the maximum value of the loss factor was1.05, andthe damping temperature range was62℃.Secondly, the polyurethane elastomer was modified by two methodes, which could beused as damping layer of restricting damping materials.(1) PZT/MWCNTs/branchedpolyurethane composites. With the addition of PZT, the tensile strength, tensile modules ofelasticity, and elongation at break of the composites were increased remarkably.The maximumvalue of the loss factor were decreased from0.98to0.89and glass transition region were alsonarrowed. Furthermore, PZT could be well dispersived in the branched polyurethane matrix.While the PZT/branched polyurethane composite was modified by MWCNTs, the tensile strength, tensile strength increased, elongation at breakdecreased, and glass transition regionwere broadened.(2) Copper wire network/branched polyurethane composites. Comparedwith the raw polyurethane material, although tanδ of the composites was decreased from0.98to0.55, but E′was improved, damping temperature range was widened and the damping peaksubstantially moved to higher temperaturezone. It suggested that the local resonance theoryplayed an important role for the damping properities of the composite, which can be used asdamping layer.Thirdly, the constraint layer of the composites were also prepared by useing E-44asmatric material, DADMT and D2000as chain extenders. And the properites of the compositewith different chain extenders content were also investigated by DSC, DMA and cantileverbeam impact tester. The composites with best dampling properties, toughness and stiffnesscould be obtained when the ratio of DADMT/D2000was0.85to0.15.Finally, structual damping materials were prepared layer by layer, and the dampingproperty was also measured by DMA in compression mode. The results showed that the tanδ,whether changed with temperature or frequency, can reach0.6or more for the initialcomposite. But the composite could only be measured accurately to300Hz due to the too softdamping layer. After adding the copper wire network, the tanδ of the composite decreasedslightly with the variation of the temperature. But tanδ was increased steadily with thevariation of frequency, which could reach1.6.