| Noise as one of the four major pollutions seriously affects people’s living environment.Sound-absorbing materials play an important role in improving people’s quality of life.Common polymer sound absorbing materials,such as polyurethane and PVC foam sound absorbing materials,are restricted by the release of harmful gases in the production process,and the sound absorbing materials used in the construction environment are hard plates.The process of placement and rewinding is more complex and occupies a relatively large space.The addition of RTV silicone rubber has the advantages of simple vulcanization process,environmental protection and controllable shape.It can be applied to interior decoration and construction of various complex production environments.However,the silicone rubber prepared by traditional technology has poor absorption effect on multi band noise and narrow absorption band.Improving the sound absorption performance of silicone rubber at different acoustic frequencies is of great significance to its development in the field of sound absorption.Three kinds of foam silicone rubber with good absorption effect on different frequency bands were prepared by filling sound absorption medium;digestion and pore forming method and direct parallel perforation method respectively.The sound absorption property and other properties of foam silicone rubber were tested and analyzed.The high frequency foam silicone rubber material(HF-LSR)with different parameters was prepared by introducing different amount of absorbing medium,LSR,into the liquid silicone rubber(HNTs).The results showed that the sound absorption performance of LSR at high frequency of 4000 Hz or above was significantly improved by adding HNTs,and at 4000 Hz,the absorption coefficient of HF-LSR with HNTs pHr of 25 pHr reached the maximum,75.8%.Compared with the blank group,the LSR increased by 42.7%,and the sound absorption coefficient at 62.5%Hz was 62.5%higher than that in the blank group LSR.In addition,the average sound absorption coefficient of HF-LSR increased with the increase of HNTs addition at high frequency 3000～5000 Hz,and the average sound absorption coefficient reached the maximum value at HNTs HNTs phr at 25 phr,which was 51.8%higher than that in the blank group.The hardness of the sample was 34.0 HO,and the rebound rate was 36.0%.The tensile strength is 0.28 MPa and the elongation at break is 125.6%.In order to widen the sound absorption frequency of liquid silicone rubber foam sound absorption material,the medium frequency foam silicone rubber material(MF-LSR)with different parameters was prepared by means of dissolution and pore forming method and adjusting the amount of pore forming agent NaCl.The results show that when the NaCl dosage is 80 phr,the absorption effect of MF-LSR on medium frequency 1000～2000 Hz sound is better than that of closed cell silicone rubber at 1000 Hz.The sound absorption coefficient of MF-LSR sample increased from 20.5%to 52.7%,increased by 157.1%;at 2000 Hz,the sound absorption coefficient of MF-LSR increased from 40.8%to 73.7%at the maximum value,and increased by 80.6%;the average sound absorption coefficient at the frequency band reached the maximum value,46.4%,which was 63.4%higher than that without open hole LSR;The density corresponding to MF-LSR is 0.4394 g/cm3,the porosity is 57.3%,the hardness is 33.0 HO,the rebound rate is 64.0%,the tensile strength is 0.19 MPa,and the elongation at break is 119.2%.Finally,through the cylindrical steel strip with different diameters in the non vulcanized colloid,the medium and low frequency foam silicone rubber sound absorbing material(MLF-LSR)with different cavity volume is prepared.The results show that the increase of the cavity diameter increases the sound absorption performance of MLF-LSR at medium and low frequency 500～2000 Hz.Compared with the cavity free structure LSR,when the single cavity cavity diameter is 5 mm,it is at 500Hz.The sound absorption coefficient increased from 7%to 23.3%,increased by 232.9%;at 1000 Hz,the sound absorption coefficient increased from 20.5%to 66.5%at the maximum value,and increased by 224.4%;the average sound absorption coefficient of the sample reached the maximum value at that frequency band,that is 40.1%,which was 67.8%higher than that of the blank group LSR sample;the hardness of the sample was 33.5 HO,the rebound rate was 48.4%,the tensile strength was 0.07 MPa,the elongation at break was 79.1%;By introducing the double cavity structure,it is found that the sound absorption performance is better than that of the single layer MLF-LSR under the same aperture in the medium and low frequency 500～2000Hz. |
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