Based On Multiple Energy Conversion, High-performance Damping Materials

Damping materials are finding numerous applications. Polymers are widely applied for damping materials because of particular structures and viscoelastic properties. The damping properties of polymers are mainly dominated by the glass transitions. The glass transition temperature(Tg) of most polymers appears at either low temperature below room temperature( such as rubber), or high temperature above room temperature(such as plastics), which are not suitable for practical application. This dissertation focuses on how to develop a high performance damping mechanism based on multi-energy transitions, which is independent or little dependant with the viscoelasticity of polymer matrix. Three sections are mainly included in this dissertation as follows: Chlorinated Polyethylene (CPE)/Piezoelectric ceramic (PZT) /Vapor Grown Carbon Fiber (VGCF) composites; CPE/ 2,2'-methylene-bis-(4-methyl-6-cyclohexylphenol) (ZKF)/VGCF composites; Organic hybrids made from CPE and small moleculesCPE/PZT/VGCF composites: The damping composites of multi-energy transitionsmechanism were produced by mixing PZT and VGCF into CPE. In this system, the mechanical vibration energy that was transmitted to CPE was found to convert into Joule's heat through conduction paths between VGCF in the polymer matrix, so the vibration fades away. In this section, conclusions are made as follows:(1 ) With the increase of VGCF content, the CPE/PZT/VGCF composite represents insulator, semiconductor and conductor. The existence of PZT has bi-directional effects on the conductive circuit of VGCF, which leads to an evident semi-conducitve plateau area in the electrical conductive curve. When VGCF volume content is low in CPE/PZT/VGCF composite, the existence of PZT can improve the VGCF distribution in CPE matrix, but the existence of PZT blocks the networks of VGCF when VGCF content is high.(2) The damping mechanism of multi-energy transitions takes effect when the VGCF content is among the semi-conductive area. When the VGCF content is low(below 8%),the VGCF conductive circuit does not form and the heat loss is quite little. When the VGCF content is higher than 20%, the transition efficiency between electric energy and heat is limited. The damping behavior of the multi-energy transitions mechanism is obvious only when the VGCF content is among semi-conductive area.(3 ) The CPE/PZT/VGCF composites can be presumed as a circuit composed of a resistance and a capacitor, which can successfully explain the phenomenon that multi-energy transitions mechanism takes effect only in the VGCF semi-conductive area.(4) Only when the resistance R=l/C, the transition efficiency between electric energy and heat reach its maximum value, which makes it possible to design the high performance damping composites of multi-energy transitions by adjusting the VGCF content.CPE/ZKF/VGCF composites: In the CPE/PZT/VGCF composites, the conversionefficiency from force to electricity is very low because of the obvious difference of rigidity between CPE and PZT, which leads to the damping effect of multi-energy transitions is not so evident as the viscoelasticity of the matrix CPE, especially during the CPE glass transition. In this section, a small organic molecule is applied to instead of PZT with the purpose to avoid the rigidity difference between CPE and PZT.(1) There is no plateau area in the conductivity curve of CPE/PZT/VGCF composite, which is due to the molecular level blending of CPE and ZKF in molten condition during the preparation of CPE/ZKF/VGCF composites, further verifying that PZT is conducive to the formation of conductive loop. Meanwhile thanks to the warping function of ZKF to VGCF, the critical value of conductivity of CPE/ZKF/VGCF composites is high.(2) The glass transition temperature(Tg) of CPE/ZKF/VGCF composites increases with the volume content of VGCF, in addition the Tg of CPE/ZKF/VGCF composite is greatlyimproved by about 20 compared with that of the matrix CPE, which indicate that in CPE/ZKF...