Preparation And Application Of Multilayer Damping And Noise-Reduced Composites

People are paying more and more attention to the sound comfort of air-conditioning products.The indicators of low-noise has gradually become one of the important indicators of the competitiveness of the air-conditioning market.The compressor is the heart of the air conditioning system,and its noise contributes significantly to the overall noise of the air conditioner.Therefore,the noise control of the compressor has become the focus of current air conditioning noise control.The sound insulation cover is an economical and effective noise reduction method.It is a hexahedral structure that closes the noise source in a relatively small space to reduce the noise from the noise source to the surrounding environment.The reasonable of structure and material design are the key of noise reduction to sound insulation cover.Based on the research of sound insulation cover,this paper develops a sound insulation cover material,which composed by multi-layer damping noise reduction materials,for noise reduction of compressors.The multi-layer damping composite material is composed by three layers of materials,and the order of materials from front to back:the first layer is a porous sound absorbing material layer,the second layer is a sound insulation layer,and the third layer is adamping layer.And the materials are tested by impedance tube,electronic tensile machine,dynamic mechanical performance analyzer and compressor noise test system.Including that:(1)different types and amounts of fillers,and proportion of rubber and plastic in the insulation material to sound insulation layer properties of density,sound insulation,mechanical properties and heat aging properties had been studied.(2)The effects of ratio of CIIR/NBR,amount of acrylonitrile in NBR,and the different kinds of fillers on the elastic modulus,loss modulus and loss factor of the dynamic mechanical properties to the damping layer had been studied.Furthermore,the dynamic mechanical properties of the damping layer at 0?-80? were tested.The comparison of the aging resistance of the damping layer was also carried out.(3)The sound absorption coefficient of the porous material to themulti-layer composite was compared and selected.At the same time,the effect of the PP/PET cotton felt in different weights,the rubber-plastic sound insulation layer in damping material layer in different thicknesses to the compressor noise reduction were studied.In this paper,the types and formulas of each layer of multi-layer damping composite materials are studied and compared,and the following conclusions are obtained.(1)In the CPE/NBR sound insulation layer,when the filler content is increased,the density increasing speed with organic montmorillonite and mica are slower than that of barium sulfate,while the increasing speed of sound insulation is faster than that of barium sulfate.On the other hand,the mechanical properties decrease with the increase of the amount of three kinds of fillers.In the proportion of CPE/NBR sound insulation layer,the increase of NBR dosage is inversely proportional to its density and sound insulation,meanwhile the mechanical properties are degraded and the performance is improved.When the ratio of CPE/NBR is 50/50,the overall performance is optimal.Atthistime,the hardness is 55 A,sound insulationis 22.1 dB,tensile strengthis 2.2 MPa and elongation at breakis 291%.(2)In the damping layer,the damping properties of CIIR/NBR composites are improved with the increase of CIIR content and acrylonitrile content in nitrile rubber.Sheet fillers such as mica powder and graphite contribute to the improvement of loss modulus and damping performance.The addition of AO-60,the damping properties of the composite can be improved significantly,reaching a maximum at 20 phr.When the amount of A0-60 is from 0 phr to 20 phr,the maximum loss factorisincreased from 0.96 to 1.22.(3)The noise reduction of the sound insulation layer on the compressor only works in 315 Hz-1000 Hz,and the increasing of its thickness has no obvious effect on the noise reduction.After the sound insulation layer is added with a weight of 400g/m~2 PET/PP porous acoustic layer,noise reduction in the full frequency band can be achieved,and the reduction in high frequency noise is obvious.Furthermore,after a damping layerisaddedbehindthe sound insulating layer,the noise hadbeen further reduced.When the thickness of the damping layer is 1.5 mm,the noise of the compressor is further reduced by 2.74 dB.