High-performance Polyurethane Damping Elastomer Based On The Effect Of Diverse Dynamic Bonds And Dangling Chains

Polymer-based damping materials equipped with good damping properties due to their unique viscoelastic properties,which can effectively reduce vibration and noise,have received more and more attention.However,the effective damping temperature range of the damping material is relatively narrow and cannot maintain high damping factor beyond its actual use temperature range.The current modification methods for broadening the effective damping behavior generally come at the expense of mechanical properties.The contradiction between damping performance and mechanical properties is difficult to balance,which seriously affects the application and development of damping materials.Aiming at the common problems of damping materials such as few existing relaxation modes and low mechanical properties,the paper intends to use the characteristics of strong structural designability of polyurethane and adopt multi-scale control strategies such as molecular and mesoscopic scales,by introducing dynamic disulfide bonds,various types of hydrogen bonding and dangling chain structure to control the intermolecular force and chain segment relaxation so as to prepare high-performance polyurethane damping material with broad temperature range.The changes in molecular structure,hydrogen bonding,crystallization,microphase separation are systematically studied to explain the effect of microstructure on the macroscopic properties of the material.First,a two-step method was adopted to introduce the aromatic disulfide and pyridine mixed chain extender to synthesize a polyurethane material with wide temperature range damping and good mechanical performance based on the dynamic disulfide exchange reaction and various types of hydrogen bonding.Dynamic mechanical analysis(DMA)showed that the effective damping temperature range of polyurethane can reach 117℃(-17℃～100℃).At the same time,polyurethane had a good mechanical properties with a tensile strength of 14.98±0.5 MPa and an enlongation at break at 710±20%).Fourier Infrared Spectroscopy(FT-IR)was used to analyze the hydrogen bonding effect and the hydrogen bond content of the system was calculated.It was found that the hydrogen bonding content had a maximum with a proper proportion of mixed chain extenders;at the same time,the temperature-changing infrared displayed that characteristic peak intensity of the hydrogen bond decreases with the increased temperature,and the characteristic peak moved to a higher wave number,that is,the hydrogen bonding dissociated.Atomic force microscope(AFM)and modulus calculations were used to explore the degree of microphase separation,the degree of microphase separation first increased and then decreased.This is the result of the combined effect of hydrogen bonding and soft and hard segment structure;Using rheological tests and broadband dielectric spectroscopy(BDRS)to analyze the movement and relaxation of the system segments,the secondary relaxation strength becomes larger with the increased disulfide bonds and the segment mobility became increased,thereby effectively improving the damping performance of polyurethane above room temperature.Additionally,the presence of aromatic disulfide bonds gives the system a certain degree of self-healing performance.The self-healing efficiency can reach 96.8% after being healed at 60℃ for 24 h,which is of great practical significance for extending the service life of damping materials.In order to further broaden the damping temperature range,besides aromatic disulfide bonds,a small amount of polymer dangling chain structure is linked to the polyurethane main chain to improve the damping performance at lower temperature.The influence of chain content,length and type on damping performance and mechanical properties is deeply studied.The results showed that the effective damping temperature range of the system after the introduction of polyethylene glycol monomethyl ether suspension chain(MPEG)can reach up to 143℃(-43℃～100℃),and the mechanical properties behaved better(11.43±0.51 MPa,870±31%).BDRS was used to characterize the molecular motion of polyurethane damping elastomer based on the synergistic effect of dangling chain and disulfide bonds,and it was found that the content of dangling chain increased,the dynamic exchange of disulfide bonds and the movement ability of chain segments improved.The unique relaxation mode of the dangling chain,the exchange of disulfide bonds,the dissociation and reconstruction process of the hydrogen bonding and the unique relaxation mode of the dangling chain all consume energy,which is conducive to the further improvement of damping performance.