Noise pollution together with water pollution and air pollution are called the three major pollutions of the contemporary era. With regard to the specific hazards of noise, there has been a marked increase in the rapid development of the industry and the construction industry, which has attracted widespread attention from countries in the world.
The most fundamental way to control noise pollution is to use sound-absorbing materials to achieve sound absorption and noise reduction. At present, there are many kinds of sound-absorbing materials, mainly in the following categories: Early natural organic materials such as cotton, hemp, and animal hides; inorganic fibers such as rock wool, glass wool, and mineral wool; and metals such as Foam aluminum, metal sound absorption tip and so on. Recently, foamed sound-absorbing materials based on synthetic polymers, such as polystyrene foams, polyurethane foams, and polypropylene foams, have been developed. In China, there are few reports on the manufacture of sound-absorbing materials using rubber polymer-modified foams. In this paper, the effects of EPR dosage, foaming agent AC content, foam thickness and foaming temperature on the sound absorption performance of EPR modified PVC foams were studied.
1Experiment 11 Major raw material grade EPR21, imported from Japan; Azodicarbonamide (foaming agent AC) industrial grade, Shaanxi Chemical General Plant product; Doctoral student of Sanyantong University, mainly engaged in preparation and modification of functional polymer materials Research work on the design and optimization of advanced inorganic materials.
(mixture of calcium stearate, strontium stearate, and lead stearate in a mass ratio of 1:1:1), chemically pure, product of Tianjin University Chemical Testing Factory; organotin, chemical pure, Xi'an Chemical Reagent Factory Chlorinated rubber (flame retardant), the mass fraction of chlorine is 0.70, chemically pure, the products of Zhejiang Gaoli Chemical Industry Corporation; the second oxide shop, the analytical pure, Hunan Yiyang Yipin smelter products; Dibutyl formate (plasticizer DBP) industrial grade, commercially available.
1.2 Basic Formulation 30; Blowing Agent AC6; Plasticizer DBP70; Three Salts 0.6; Organotin 1.5; Chlorinated Rubber 2; Antimony Trioxide 1. 1.3 Main Test Equipment SR-160B Open Type Plastic Machine, Shanghai Rubber Machinery Factory Products; 101-Z Drying Box, Shanghai Testing Instrument Factory Product; ND-2 Filter, State-run Red Sound Equipment Factory Product; 2010 Heterodyne Analyzer, Denmark BK Products; Standing Wave Tube, Homemade .
1.4 Sample Preparation Sample preparation process: raw material preparation - stirring and mixing * open mill mixing - a piece of film ※ slices ※ foaming in the oven ※ knock out the film ※ sample size measurement. Process conditions: mixing temperature 120 °C; mixing time 8min; foaming temperature 196 °C; foaming time 10min. 1.5 Determination of sound absorption coefficient Sound absorption coefficient of foam materials using standing wave tube method, specifically tested Refer to 2 Results and Discussion 21 The effect of EPR dosage on the sound absorption performance of foam materials is drastically reduced, which seriously affects the sound absorption performance of the material.
2.2 The effect of the amount of foaming agent on the sound absorption performance of the foam material can be seen, with the increase in the amount of EPR, the sound absorption factor at the frequency below 1000 Hz showed an increasing trend, while the sound absorption factor at the frequency above 1000 Hz showed a decreasing change. The trend is that EPR can improve the overall sound absorption performance (in terms of average sound absorption factor) of foams compared to foams without EPR. The reasons are: 1 At room temperature, EPR is in a highly elastic state when sound waves are present. When it is in action, it will elastically deform itself, which will consume some acoustic energy; 2 The chain segments and side groups on the EPR macromolecular chain generate motion under the action of sound waves, and this motion has greater friction resistance within the molecule and/or between molecules. The consumption of sound energy is significant. Therefore, EPR is beneficial to the improvement of the comprehensive sound absorption performance of materials. Because the glass transition temperature of EPR is much lower than that of PVC, the energy that causes EPR deformation and the movement of its molecular segments is relatively low. Therefore, within a certain range, the increase in the amount of EPR in the composite material makes it relatively low frequency. The improvement of the sound absorption factor is obvious. However, it is not that the greater the amount of EPR, the better the overall sound absorption performance of the material, because when the amount of EPR is too large, the viscosity of the system during foaming will be too small, and with the rapid decomposition of foaming agent, the foaming gas will increase rapidly. The rapid growth of cells, the rapid thinning of the vesicles causes the adjacent cells to foam and blister. The cell structure deteriorates, resulting in decreased porosity, and the sound absorption performance of the material also decreases. When the foaming is severe, it can also cause the cells to collapse and the pores of the material can be seen. With the increase of the amount of blowing agent AC, the sound absorption performance in the low frequency range is reduced, and the sound absorption performance is gradually improved in the middle and high frequency range. Increased. This is because as the amount of the foaming agent increases, the foaming gas which is decomposed during foaming increases, the cell structure inside the foam is improved, and the porosity of the material is improved. The general rule of the influence of porosity on the sound absorption performance of the material is: With the increase of porosity, the sound absorption performance of middle and high frequencies is improved, and the sound absorption performance at low frequency is reduced. The results of this experiment are consistent with this basic law. However, the amount of the foaming agent should not be too much. Otherwise, the cellular structure of the foamed product may be roughened or collapsed, resulting in a sharp drop in the sound absorption performance of the material.
2.3 Effect of Material Thickness on Sound Absorption Performance of Foam Material Using the basic formula, the effect of material thickness on the sound absorption performance of the specimen is visible, with the increase of the material thickness, the sound absorption performance is improved, and the sound absorption performance in the low frequency range. The increase is even more pronounced. This is because the thickness increases, sound absorption inside the material is more sufficient, the reflected sound wave is reduced, and the sound absorption performance is improved. However, it is not possible to increase the sound absorption performance by simply increasing the thickness of the material, because as the thickness increases, the improvement of the sound absorption performance is continuously reduced, and the material thickness is also limited by the actual use of space. Therefore, the choice of material thickness should be comprehensively considered from factors such as sound absorption performance and use space. In addition, the sound absorption performance can also be improved by changing the depth of the cavity behind the material.
Frequency / Hz material thickness impact on the sound absorption properties of foam materials 2.4 foam temperature on the sound absorption properties of foam materials In addition to the amount of formula ingredients, the preparation process conditions have an important impact on the sound absorption properties of the material. The influence of the foaming temperature on the sound absorption performance can be seen.
It can be seen that as the foaming temperature increases, the sound absorption factor in the low frequency range continuously rises, while the sound absorption coefficient in the middle and high frequency ranges decreases slightly. This is because as the foaming temperature increases, the foaming agent is more completely decomposed, its residual amount in the system is reduced, the cell structure of the system is improved, and the sound absorption coefficient in the low frequency range is improved, and the high frequency Acoustic waves are absorbed on the surface of the material. As the temperature increases, chemical and physical effects such as thermal degradation may occur on the surface of the material, which deteriorates the structure of the surface and reduces the absorption of high-frequency sound waves by the material.
3 Conclusion EPR can significantly improve the sound absorption properties of PVC foam. With the increase of the dosage, the low frequency sound absorption performance of the foam material is significantly improved, and the high frequency sound absorption performance is slightly reduced.
The increase in the amount of foaming agent can significantly improve the mid-high frequency sound absorption performance, but the low-frequency sound absorption performance has been reduced.
The increase of material thickness can increase the sound absorption coefficient of the whole frequency band, and the improvement of the low frequency sound absorption coefficient is even more significant.
With the increase of the foaming temperature, the low-frequency sound absorption performance is improved, and the sound absorption performance of the middle-high frequency is reduced.
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