Investigation Of The Damping Properties Of Organic Polar Molecules/ACM?NBR Composites Using Molecular Dynamics Simulations In Combination With Experimental Methods

Currently, the investigation of polymer damping materials has drawn much of its attention in materials research field. In this paper, the microstructure and condensed properties of a series of small polar organic molecules/rubber composites were studied through molecular dynamics simulation. Using molecular dynamics simulation, we calculated the charge distribution of the atoms to forecast the types and numbers of the hydrogen bonds. Then, thermal and dynamic mechanical characterization of molecular dynamics was performed to verify the simulation accuracy. The main conclusions are as follows:(1) Hindered phenol AO-80/polyacrylate rubber damping hybrids are novel damping materials. They were fabricated to study the influence of the content of the AO-80 on their damping performance and mechanical properties. Molecule dynamics (MD) simulation, a molecular-level method, was applied to elucidate the microstructure and mechanism of the hybrids through the radial distribution function (RDF), fractional free volume (FFV), and cohesive energy density (CED). MD simulation results revealed that three types of hydrogen bonds, namely, type A (AO-80)-OH…O=C-(ACM), type B (AO-80)-OH…O=C-(AO-80), and type C (AO-80)-OH…OH-(AO-80), were formed in the AO-80/ACM hybrids. Meanwhile, the experimental results using positron annihilation lifetime spectrometry (PALS), differential scanning calorimetric (DSC), Fourier transform infrared spectroscopy (FTIR), and dynamic mechanical thermal analysis (DMTA) found that the introduction of AO-80 could remarkably improve the damping properties of the hybrids, including an increase in the glass transition temperature (Tg) as well as the loss factor (tan ?).(2) Molecule dynamics simulation was used to predict the damping properties of AO-60/polyacrylate rubber (AO-60/ACM) composites before experimental measures were performed. MD simulation results revealed that two types of hydrogen bond, namely, type A (AO-60)-OH…O=C-(ACM), type B (AO-60)-OH…O=C-(AO-60) were formed. Then, the AO-60/ACM composites were fabricated and tested to verify the accuracy of the MD simulation through FTIR, DSC, and DMTA. FTIR results confirmed the MD simulation results that two types of hydrogen bond were formed in the AO-60/ACM composites if the addition amount of AO-60 reached 58 phr. DSC and DMTA results found that the introduction of AO-60 could remarkably improve the damping properties of the composites, including the increase of glass transition temperature (Tg) alongside with the loss factor (tan ?), indicating the AO-60/ACM(98/100) had the best damping performance amongst the composites, consistent with the fractional free volume (FFV) and the cohesive energy density (CED) results calculated by MD simulation.(3) In this part, the BPA/NBR composite materials containing large amounts of hydrogen bonds were prepared to deeply investigate the influence of hydrogen bond network on the damping properties. The atomic charge distribution was obtained using molecular dynamics simulation to calculate the radial distribution functions between (BPA)-OH…N?C-(NBR) and (BPA)-OH…O-(BPA). DSC and DMTA results found that composites with 61 phr BPA could remarkably improve the damping properties of the composites, including the increase of glass transition temperature (Tg) alongside with the loss factor (tan ?), indicating the BPA/NBR (61/100) had the best damping performance amongst the composites, consistent with the fractional free volume (FFV) and the cohesive energy density (CED) results.