Study On High Acoustic Damping Rubber Composites And Its Application In Underwater Sound Absorption

Due to unique viscoelastic, rubber is widely used for damping, vibration reduction, noise weakening and sound absorption. Thus, acoustic damping rubber materials used for underwater sound absorption received experts’ extensive attention in recent years. In this thesis, nitrile rubber (NBR) composites were prepared, the influence of the acrylonitrile content, the kind and amount of plasticizer, the carbon black particle size and other inorganic filler on physical mechanical, dynamic mechanical, thermal and acoustic damping properties of composites were studyed. Further, have explored the influence of organic hybrid (hydrogen bond) and gradient laminated technology on acoustic damping performance of different rubber. Moreover, the ruber materals’amplification process was determined. Through above work, the following meaningful conclusions were obtained:(1) NBR composites showed excellent acoustic damping performance as its E’at the range of 1×108 to 7×108 Pa or even lower and its tanδ remain at 0.5 to 0.9 or even higher when the frequency range 103 to 104 Hz; Choosing low acrylonitrile content of NBR matrix and adding plasticizer contributes to lower Tg and E’for NBR composites. When acrylonitrile content is 18%, the dosage of DOP as plasticizer accounts for 15 phr, NBR composites showed excellent acoustic damping performance.(2) Particle Size of carbon black has influence on reinforcement efficiency, but slightly impacts on acoustic damping properties of NBR. NBR, natural rubber (NR), styrene butadiene rubber (SBR), and hybrid materials showed a higher average absorption coeffic ient when sound frequency range 3 to 8 kHz and the absorption coefficient under relatively high level of frequency when they filled with talcum, owing to increasing of their density. As porous filler, hollow glass microspheres (HGMs) can effectively improve the mechanical properties of NBR composites and the acoustic damping performance of the material above 4.3 kHz of sound frequency.(3) High acrylonitrile content (41%) of AO-80/NBR hybrid materials obtaining excellent mechanical properties and damping performance because of hydrogen bonding network structure, and ten percent of AO-80 contributes to the form of weak hydrogen bond network structure, which effectively improves the acoustic damping performance of the hybrid materials; But hydrogen bond network structure can only improve tensile strength and the sound absorption coefficient above 4.5 kHz in low acrylonitrile content (18%) of AO-80/NBR hybrid materials. Adding the dosage of hindered phenol could reduce AO-80/MPU hybrid materials’ density, hardness, tensile strength and tear strength, arise its Tg, and change its damping performance; When the dosage of AO-80 is 10 phr, material’s peak value of loss peak is as high as 0.87, but this dosage of AO-80 did not affect positively on acoustic damping performance of hybrid material.(4) The gradient laminated materials prepared by using MPU with a low reflection coefficient as sound incident side and NBR with high internal friction as reflection side had excellent acoustic damping performance. This gradient laminated method can effectively improve the acoustic damping performance of the NBR, especially high acrylonitrile content of NBR.(5) Have explored and determined the amplification process of NBR acoustic damping rubber materials and AO-80/NBR composite used for vibration restraining. This process can produce gross rubber more than 50 kilogram per batch, and the performance of vulcanized rubber or product is consistent with the performance of first experiment product.