Study On Preparation And Absorption Properties Of Eucommia Ulmoides Gum/polyurethane Composites

Underwater sound absorbing materials play an important role in submarine stealth and underwater acoustic communication.Due to the development of sonar technology and the demand of deep-sea operation,it has become the focus of our research that sound-absorbing materials can still maintain good sound absorption performance under low frequency and high hydrostatic pressure.Polyurethane elastomers have good damping properties and excellent mechanical properties,which are usually used in the preparation of anechoic coatings,sound absorption foams and so on.Because of its unique rubber-plastic duality,eucommia ulmoides gum(EUG)can be used with other polymer materials to produce composites with excellent properties,which has become a research hotspot of acoustic damping materials in recent years.In this paper,mixed polyurethane(MPU)and EUG were blended to prepare composites.By adjusting the blending ratio and cross-linking degree,and making use of the self-crystallization properties of EUG at low vulcanization degree,it is expected to obtain a kind of underwater sound-absorbing composites with good low-frequency sound absorption properties and high hydrostatic pressure resistance.The first part(chapter 3)of the paper studies the co-vulcanization of EUG and MPU.Different vulcanization systems of EUG and MPU were designed,and the vulcanization characteristics,mechanical properties,peel strength,dynamic mechanical properties and co-vulcanization interface morphology of the materials were tested.It was found that when the vulcanization system was 1 phr accelerator DZ,and 2 phr sulfur,the T10 and T90 of EUG were similar to those of MPU.The mechanical propertie of MPU/EUG blend is the best,the cross section of peel has good blending property,and the co-vulcanization effect is remarkable,so it is determined to be our preferred vulcanization system.The processing technology of MPU/EUG mixed rubber was determined:MPU and EUG were mixed separately,and then the mixed rubber and process parameters were obtained.The second part(chapter 4)of the paper studies the effect of different MPU/EUG ratios on the structure and properties of MPU/EUG composites.Characterization and analysis of the sample's microstructure,crystallization properties,vulcanization characteristics,mechanical properties,dynamic mechanical properties and sound absorption properties,etc.It was found that with the increase of the proportion of EUG,the micro-surface of the composites became rough and cracks appeared,indicating that the compatibility of EUG and MPU gradually deteriorated.The loss factor(tan?)of MPU/EUG composites decreased with the increase of the proportion of EUG,When 30 phr of EUG was added,the peak value of tan? decreased from 0.79 to 0.64.In the range of-50?-40?,the storage modulus E'of the composites increases obviously with the increase of EUG proportion.The addition of EUG improves the sound absorption properties of MPU/EUG composites in 4.5kHz-8kHz frequency domain.Under 0.1MPa pressure,the average sound absorption coefficient of MPU/EUG(70/30)composites is 0.892,which is 52.2%higher than that of pure MPU.The average sound absorption coefficient of the composite reaches 0.688 under 4MPa pressure.It shows that the material has good sound absorption resistance to hydrostatic pressure.The third part(chapter 5)of the paper studies the effect of adding HGM on the properties of MPU/EUG composites.It was found found that with the addition of HGM,the loss factor of the MPU/EUG composite material decreased.When 20 phr of HGM were added,the peak value of tan?was 0.58.when the temperature was higher than-25?,the storage modulus E'of the composite material increased with the content of HGM.HGM will hinder the crystallization of EUG,and the crystallinity of the composite material will gradually decrease with the addition of HGM.Under 0.1MPa pressure,the MPU/EUG/HGM(70/30/5)composite material has the best sound absorption performance.The average sound absorption coefficient in the 3kHz-8kHz frequency domain is 0.839,which is 11.9%higher than when HGM is not added.And the composite material has a tensile strength of 26.1 MPa and a breaking elongation of 509%.It shows that MPU/EUG/HGM(70/30/5)composite material has excellent sound absorption and mechanical properties.