Sound Absorption And Insulation Of Laminated Porous Nitrile Rubber-based Composite Materials

The problem of Environmental noise is getting more and more serious, it has already affect people's life, work and study. Because of its small characteristic impedance, large viscosity, the absorbed energy can be transformed into thermal energy very well. The rubber's sound absorption performance is better than metals, especially in high impact frequency, so rubber is often used as the sound-absorbing material. Nitrile butadiene rubber (NBR) is unregulated copolymers made by butadiene and acrylonitrile's polymerization.The molecular chain has polarity-CN, and has oil resistance, benzene resistance, heat resistance, hydrocarbon performance. In order to get broadband reducing noise materials, mostly it is made to multi-layer structure so as to improve its acoustic properties. generally it was mixxed in vermiculite to improve the material internal loss that can increase the vulcanizates'effective loss factor, improve the sound absorption performance in the low- frequency and widen frequency range.Testing samples are obtained through mixing, weighing, hot forming three steps.It is found by added content of vermiculite in NBR, hot-pressing time, thickness effect greatly on the sound absorption performance of the single-layer rubber sample. Research shows that when the compression strength is 5Mp, hot-pressing temperature is 160℃,venniculite contents is 35%, hot-pressing time is 12min, the sound absorption and sound insulation performance of samples will be optimal, sound absorption performance of samples in middle-frequency and high frequency is improved. Compared with the rubber sample without vermiculite, the sound absorption performance moved to low-frequency, sound insulation performance is better; under the same material and the same density, the absorption coefficient of samples is improved from 0.15 to 0.75, sound insulation volume is increased 8dB with the increase of the thickness of the material. Based on the single-layer sample, the multilayer vermiculite/NBR composite samples are studied. Firstly,the glue is used for adhesive, middle- layer is ramie fabric, sewing spacing is 1.5 cm, suturing way is lock suture, the acoustic properties effected by the test method, number of layers of middle layers and in different surface layer sample combinations are researched and analysized. It's shown that when the surface layer samples are ensured, the number of the ramie fabric layer is 2,3,4 layer, the sound absorption coefficient of samples is improved from 0.2 to 0.4, sound insulation volume is increased 4dB.When the surface layer samples are the same, the sound absorption and insulation performance of the sample is poor. When the percentage of vermiculite contents is 15%, the best acoustics performance can be obtained.