Noise-reduction coatings based on interfacial hydrogen bonding between hindered phenol/epoxy microspheres and waterborne polyurethane

Waterborne damping materials have the advantages of reducing noise pollution and air pollution. Hybridization with hindered phenol is an effective method to improve damping properties of polymer materials, but this method is limited by the insolubility of hindered phenol. Therefore, it is still an issue to use hindered phenol for improving the damping properties of waterborne polymer materials. In this paper, diglycidylether of bisphenol A (DGEBA) and 3,9-bia [1,1-dimethyl-2-{β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) were used to prepare hindered phenol/epoxy microspheres by direct curing in emulsion containing montmorillonite (MMT). The accumulation of hindered phenol on microsphere surface led to the interfacial hydrogen bonding between microspheres and waterborne polyurethane (WPU), while noise-reduction coatings were prepared by direct compounding. The existence and variation of hydrogen bonds in the materials were investigated. Scanning Electron Microscopy (SEM) and Optical Microscope Analysis (OM) test shows that the particle size of microspheres was directly proportional to AO-80 content and inversely proportional to MMT content. Fourier Transform Infrared Spectrum (FTIR) test proves that the number of interfacial hydrogen bonds between WPU and microspheres was directly proportional to the content of AO-80 on the surface of microspheres and inversely proportional to the particle size of microspheres. The optimal formulation of microspheres is that the ratio of epoxy, AO-80 and MMT is 10: 7: 5 (EAM 1075), and the particle size of microspheres is 20–30 μm. When the ratio of WPU to EAM1075 was 10: 5, according to Dynamic Mechanical Thermal Analysis (DMTA) test, the overall damping capacity of the composite material is improved, its loss factor increased from 0.15 to 0.45 at room temperature, and the damping temperature range of the material was also broadened. Through acoustic resistance test and noise reduction test, the noise reduction effect of the composite coating reached 30 dB.