Study on under-water sound absorption properties of Eucommia ulmoides gum and its blends

The sound absorption performances of Eucommia ulmoides (EU) gum and its blends with conventional damping rubber are studied systematically. Blending 20%, 40% EU gum into chlorobutadiene rubber (CR), their under-water sound absorption property at 3-20 kHz is better obviously than that of CR. Blending 10, 20, 30, and 40% EU gum into chlorinated isobutene-isoprene rubber (CIIR), their sound absorption properties at 3-20 kHz are also better obviously than those of CIIR, especially the SAC of EU gum/CIIR (20/80) at 3 kHz is equal to 76% which is a great increase at low frequency region. The results show that a critical blend ratio of EU gum exists which is equal to 50%, if EU gum > 50%, their under-water sound absorption properties are very poor, if EU gum < 50%, their under-water sound absorption properties are very good. The relaxation absorption of damping rubber, the spacial diffuse reflection absorption of EU gum crystallites, and the shear deformation absorption in the interface between crystalline hard phase and rubber soft phase are the three main reasons to contribute their under-water sound absorption properties. In addition, reducing crosslinking degree can increase under-water sound absorption property.