Study On Preparation Of PMMA-NMMT/Vinyl-terminated Polydimethylsiloxane Composite And Its Sound Absorption And Insulation Properties At Low And Medium Frequencies

Aiming at the technical problems of universality,strong penetration and difficult treatment of medium and low frequency noise,porous polymer microspheres/liquid silicone rubber composites with certain sound absorption and sound insulation ability were designed and synthesized in this study.Taking advantage of the excellent sound absorption performance of porous materials,the liquid silicone rubber material can be modified in the treatment of medium and low frequency noise on the premise of good sound insulation performance.Based on the structure and performance of the material,a new design idea and method for medium and low frequency sound absorption and noise reduction materials are provided.In this thesis,polymethyl methacrylate was synthesized by free radical polymerization w ith methyl methacrylate as raw material,azobisisobutyronitrile as initiator and polyethylene glycol as pore-forming agent,and then coated with sodium montmorillonite(NMMT)which was dispersed in water by the aid of cetyltrimethylammonium bromide.And PMMA-NMMT porous micro-pores were prepared by template method.Using vinyl-terminated polydimethylsiloxane as matrix,polymethylhydrosiloxane as crosslinking agent,2-methyl-3-butyne-2-alcohol as inhibitor,fumed silica as reinforcing agent,liquid silicone rubber foaming material was prepared by vulcanization under certain technological conditions under the action of platinum catalyst.As a modified material,the prepared porous microspheres were added into the vulcanization process of liquid silicone rubber,and PMMA-NMMT/vinyl-terminated polydimethylsiloxane composite was successfully prepared.The structure of the material was characterized by FT-IR,SEM,TG,BET,laser particle size test,mercury intrusion test and so on.The process of preparing liquid silicone rubber foaming material was discussed.The effects of the dosage of microspheres,foaming agent,foaming temperature and heat preservation time on the sound absorption and insulation performances of the product were studied.The main conclusions are summarized as follows:(1)With the increasing of foaming agent content in materials,the total pore volume,average pore size and porosity of products are increased.The total pore volume and porosity of product with 10%foaming agent is higher than the product with 4%foaming agent by 174%and 16.41%.(2)With the increasing of PMMA-NMMT microspheres content,the sound insulation performance of the material for middle and low frequency noise is significantly improved,and the sound absorption performance for low frequency noise is also improved to some extent.The average sound insulation performance of the product with 10%microspheres is 44.24%higher than that of the product without microspheres.When the content of foaming agent is 4%,the sound absorption and insulation performance of the material is good for the noise in the middle and low frequency bands.With the increase of foaming temperature,the sound absorption performance of materials for low and medium frequency noise will be improved,while the sound insulation performance will be decreased.The average sound absorption coefficient of products with foaming temperature of 150℃ for low-frequency noise is 33.33%higher than that of products with foaming temperature of 100℃.However,with the increase of heat preservation time,the sound absorption performance of the material for low frequency noise will decrease,while that for medium frequency noise will increase.When the heat preservation time is 30 minutes,the sound insulation performance of the material for medium and low frequency noise is the best.(3)When other conditions are the same,the mechanical properties of PMMA-NMMT microspheres are improved,and the tensile strength of the product is increased by 62.5%.