| As the morden industry age approaches, damping materials, which can decrease vibration and noise pollution, have been widely used in the fields such as transportation, machinery manufacture, architectural decoration, precision instrument, and military equipment. But for different applied fields, the requirement of the damping properties is usually varied. In order to absorb multi-band vibration wave effectively, it is urgent to develop a new kind of damping material with relatively higher damping peak and relatively broader damping temperature range. As with polymer based damping materials, their molecular chains begin to move near the glass transition temperature, so much energy is depleted so that the materials have relatively high damping peak. However, for common homopolymers, the glass transition temperature range is only from20℃to30℃, which can not meet the requirement of practical application. Therefore, the damping temperature range of polymers is generally broadened by the means that two or more polymers are blended, or experience copolymerization modification and construction of interpenetrating polymer network. These methods can broaden the damping temperature range, yet will usually decrease the damping peak simultaneously. Consequently, how to reach the balance of damping temperature range and damping peak is an urgent problem.In this study, by graft copolymerization modification, polyether type polyurethane with different soft segments and epoxy resin were polymerized firstly. Then, interpenetrating polymer network of epoxy resin and polyether type polyurethane after grafting was formed to broaden the damping temperature range via a stepwise cure process. Nevertheless, in order to not decrease the damping peak at the same time that the damping temperature range is broadened, the tetrapod-shaped ZnO whisker (T-ZnO whisker), piezoelectric lead zirconate titanate (PZT) and mesoporous molecular sieve (MCM-41) with special structures or properties were incorporated into the matrix of interpenetrating polymer network. At last, we got the functional hybrid composites with good damping properties. Still, the mechanism and the effect of graft copolymerization modification, interpenetrating polymer network, and functional particles on the damping properties of polymers were studied in details, which are as follows:(1) Graft copolymers of polyether type polyurethane and epoxy resin were synthesized by polyethylene glycol (PEG), polypropylene glycol (PPG), and polytetrahydrofuran (PTMG) respectively with different structure of molecular chains. Results of dynamic mechanical thermal analysis (DMA) showed all graft copolymers had the trend of single peak, but graft copolymerization could broaden the damping temperature range effectively. Among the three polyether polyols, the PEG type graft copolymers had the biggest value of loss factor peak, while PPG type graft copolymers had the broadest effective damping peak values. And the ratio of polyether type polyurethane to epoxy resin had great effect on the appearance position of the damping peak value and effective damping temperature range. Compared with that of epoxy, if the ratio of PPG to EP was70:30, the most broad effective damping temperature range (tanδ≥0.3) could be broadened from47.0℃to120.3℃, but the loss peak value decrease from1.44to0.63.(2) After construction of graft interpenetrating polymer network consisting of polyether type polyurethane-epoxy resin and polyester type polyurethane, the effective damping temperature range of material was broadened to178.8℃, but the loss peak value still remained1.10. So, good damping effect was gained. By thermogravimetric analysis, it was shown that IPN structure could improve the heat resistance of polymers but its effective temperature range was limited. By scanning electron microscopy and transmission electron microscopy, it was found that polyether type polyurethane-epoxy resin appeared interpenetrating connected cylinders in the polyether type polyurethane matrix.(3) When T-ZnO whiskers were incorporated into the graft interpenetrating polymer network, it was found by DMA that T-ZnO whiskers made the damping peak value of composite increase, and the enhanced effect of the low-temperature peak value was better than that of the high-temperature peak value. When the content of T-ZnO whiskers was10wt.%, the biggest loss peak value reached1.44, while the effective damping temperature range still remained168.7℃. Also, T-ZnO whiskers helped improve the heat resistance and mechanical properties of material.(4) For the damping composite consisting of mesoporous molecular sieve and graft interpenetrating polymer network, when the content of molecular sieve was below10wt.%, the loss factor peak value and the temperature that the peak appeared were elevated as the content of mesoporous molecular sieve increased, and the biggest loss factor value reached1.34. However, when the content of mesoporous molecular sieve was more than10wt.%, the loss peak value decreased rapidly. Compared with polymer matrix, because the mesoporous molecular sieve resisted the heat conduction, the one-set temperature of composite was increased with30"C, which demonstrated the heat resistance of the composite was enhanced, and the tensile strength of the composite was elevated20%.(5) For piezoelectric effect, when the lead zirconate titanate was incorporated into the graft interpenetrating polymer network, the damping value of material was enhanced largely, and incorporation of conductive carbon black made the damping peak value reach2.38. But the content of carbon black had a threshold value, and the best damping effect could be gained only when appropriate electroconductibility was reached. By XRD, SEM, TG and so on, the structure and properties of the composite were characterized. Furthermore, from the perspective of mechanical property, small quantity of PZT and conductive carbon black can enhance the mechanical property of the composite. On the contrary, if the content of PZT and conductive carbon black is too much, the internal defects of the composite increase so that its mechanical property is decreased.In conclusion, both graft copolymerization and interpenetrating polymer network can significantly broaden the effective damping temperature range of polymer matrix. And by changing the ratio of reactants, the appearance position of peak and the width of damping peak can be regulated. In addition, the functional particles with special structure and property can enhance the damping peak of composite without affecting the damping temperature range. And the incorporation of functional particles and interpenetrating polymer network also can enhance the thermal stability and mechanical property of material.So the functional particles hybrid interpenetrating polymer network gains quite good comprehensive properties, which should have a wide application prospect. |
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