| Noise pollution is known as one of the "three major pollutions",which poses great harm to people’s mental and physical health.With the continuous development of urban road construction and rail transit,residents on both sides of the road or rail will be exposed to traffic noise for a long time.Thus effective measures to reduce traffic noise are urgently needed.As a common noise reduction facility,sound barriers can absorb or insulate most high-frequency noise by internal sound absorbing or insulating materials.However,urban traffic noise is mainly medium to low frequency(0-2000Hz)noise,and the noise reduction performance of sound barriers is poor.In order to improve the absorption and barrier ability of the sound barrier to low-frequency noise,this thesis synthesized a water-based lotion with high damping performance,which was used as the base material to prepare water-based damping coating as the noise reduction performance enhancement material of the sound barrier,and studied the factors affecting the damping performance and noise reduction performance,so as to propose a solution to the problem of how to effectively reduce urban low-frequency traffic noise.Firstly,the aqueous polyurethane lotion(WPU)was prepared by using isophorone diisocyanate(IPDI)and polypropylene glycol(PPG)with molecular weight of 2000 as main raw materials,introducing hydrophilic groups by adding aqueous chain extender DMPA,and increasing molecular weight by using small molecule chain extender1,4-butanediol(1,4-BDO).The effects of crosslinking agent TMP,siloxane coupling agent KH550 and R value(-NCO/-OH)on the properties of WPU were studied.The results showed that the water resistance of WPU lotion film could be improved with the increase of crosslinking agent,silica coupling agent and R value,but the stability will be reduced.With the increase of WPA content,the water resistance and loss factor of the blended WPUA lotion film improved,and the damping temperature range narrowed and gradually moved to the high temperature direction.When the mass ratio of WPU:WPA=8:2,the maximum loss factor of the blended lotion was 0.91,the damping temperature range(the temperature range where the loss factor was greater than 0.3)was 69.1 ℃,and the effective damping temperature range was 46.8 ℃-115.9 ℃.When polyacrylate is added during the polyurethane synthesis process,the damping temperature range is increased to 95 ℃,but the loss factor is significantly reduced.Secondly,the monomers of butyl acrylate(BA)and methyl methacrylate(MMA)used to synthesize WPA were swelled in the molecular structure of WPU to initiate the polymerization of acrylate monomers,forming a waterborne polyurethane/waterborne polyacrylate lotion(IPN-WPUA)with interpenetrating polymer network(IPN)structure.The effects of PU/PA,crosslinking degree,molecular side chain length,and the number of hydrogen bonds on the properties of IPN-WPUA lotion film were investigated.Calculate the solubility parameters and binding energy of WPU,WPA and IPN-WPUA through molecular simulation,judge the compatibility of the two resins,calculate the free volume fraction and hydrogen bond number of each lotion,and explore the change of damping performance from a microscopic perspective.The results showed that WPU and WPA had similar solubility parameters and adsorption,indicating that they had good compatibility.The increase of PU ratio,cross-linking degree and the number of hydrogen bonds would increase the loss factor of IPN-WPUA lotion film,but the excessive cross-linking degree and the number of hydrogen bonds would reduce the loss factor.The side chain length of the molecular chain can affect the flexibility of the molecular chain,the number of hydrogen bonds and the size of the intramolecular free volume,and the appropriate side chain length can significantly affect the damping temperature range of the lotion film.When butyl acrylate and butyl methacrylate are used as PA monomers,the IPN-WPUA lotion has the widest damping temperature range(100 ℃),and the maximum loss factor is 0.72.Finally,commercial WPA lotion was blended with IPN-WPUA lotion to further improve the loss factor and mechanical properties,and a blended lotion with damping temperature range of 150 ℃(-50 ℃～100 ℃)and loss factor of 0.98 was obtained.With this lotion as the base material,mica powder,hollow glass beads and talc powder as the filler,the performance is adjusted by adding appropriate additives,A water-based damping coating is prepared,and a composite noise reduction material is prepared by coating the damping coating on the back of the polyester fiber sound absorbing material for the sound barrier.The influence of filler ratio on the damping performance of coatings was investigated through orthogonal experiments,and the sound absorption,water absorption,and sound insulation capacities of water-based damping coatings,polyester fiber sound absorbing materials,and composite noise reduction materials were tested.The relationship between coating thickness and noise reduction performance of materials was also studied.Research has shown that the addition of fillers can reduce the loss factor and shift the peak of the loss factor towards low temperatures;Mica powder has the greatest impact on the loss factor of coatings,while talc powder has the greatest impact on the TA value(integral area of the loss factor above 0.3 in the material’s loss factor temperature curve)and glass transition temperature of coatings;The change in thickness has no effect on the sound absorption coefficient of the material,but thicker materials can isolate more sound.A 1cm thick coating has the best noise reduction effect,with a sound absorption coefficient between 0.25 and 0.35 at mid to low frequencies and a sound insulation level between 3d B and 12.5d B.The sound absorption coefficient of polyester fiber sound-absorbing materials is around 0.58,and the sound insulation amount is 1d B.The maximum sound absorption coefficient of composite noise reducing materials can reach 0.62,and the maximum sound insulation amount can reach 23 d B,indicating that the prepared water-based damping coating can effectively improve the noise reduction performance of the sound barrier. |
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