Study On The Preparation And Characterization Of The Polyurethane Based Composite

With the rapid development in the fields of aerospace, military equipment, precision instruments etc., in addition to the requirement of high strength .and excellent corrosion resistance for the high damping materials, the intelligence feature of adapting to the various working environments needs to be satisfied. Therefore,it is a trend to develop damping materials with intelligent properties.In this thesis, the carbon nanotubes (CNTs)/polyurethane (PU) composites and CNTs/NiTi spring/PU composites were prepared by solution-forming method and hot-pressing method by making use of the merits of CNTs with large specific surface area and high mechanical property and advantages of NiTi exhibiting poseudoelasticity and shape memory effect. Then the mechanical property, damping property, microstructure and shape memory effect were investigated by using an universal materials testing machine, DMA, SEM and home-made shape recovery testing equipment, respectively.The results of the solution-forming composites show that, the elastic modulus, mechanical strength, and loss factor are improved due to the addition of CNTs for the CNTs /PU composites. The improvement of mechanical property is caused by the reinforcement of CNTs,and the enhancement of damping property is attributed to the interfacial frictions between the CNTs and matrix. When the CNTs content was 0.1wt%, the composite exhibited a good comprehensive property with tensile strength of 12 MPa, elastic modulus of 23 MPa and loss factor of 0.385. For the CNTs/NiTi spring/PU composites, NiTi spring has been added to increase the elastic modulus, mechanical strength and loss factor, and the strain recovery increases under large deformation. This mainly benefits from the reinforcing effect of NiTi spring and the superelastic recovery under mechanical cycling of the spring. When the content of CNTs was 0.5wt%, the composite exhibited a good comprehensive property with tensile strength of 14 MPa, elastic modulus of 29 MPa and loss factor of 0.43.The results of the hot-pressing composites show that, with the increase of CNTs content,the elastic modulus increased first and then decreased,and the loss factor changed little.When the content of CNTs was 1wt%, the composite presented a relatively good comprehensive property with tensile strength of 14 MPa, elastic modulus of 25 MPa and loss factor of 0.368. For the CNTs/NiTi spring/PU composites, the addition of NiTi is capable to improve the energy absorption under large deformation. When the addition of CNTs was 0.3wt%,tensile strength was 14 MPa and the elastic modulus was 30 MPa. When the addition of CNTs was 0.1wt%, the loss factor of 0.414 was the highest.Microstructure observation showed that the CNTs was well dispersed in the PU matrix and the interfacial bonding between the CNTs, NiTi spring and matrix was good for the composites prepared by the above two methods. The shape memory effect testing showed that the NiTi alloy dominated shape memory effect was better than the shape memory effect dominated by PU matrix.