Molecular Dynamic Simulation And Dynamic Mechanical Properties Analysis Of Nitrile-butadiene Rubber Composites

Molecular dynamics (MD) simulation and experimental methods are used to quantitatively analyze the microstrcutures of polar organic molecules/ nitrile-butadiene rubber (NBR) composites at the molecular level in this study. We expected to establish correlations between the microstructures and the damping properties. Such correlations are expected to be useful for understanding the fundamental damping mechanism of organic molecules/ NBR composites. Compatibility is the key factor in choosing organic hybrid components and determining structure and performance. As an important strategic resource, it is necessary for rubber damping materials to get higher performances. NBR/PVC is a miscible physical composite of commercial importance. The new application of this composite would bring more surprise. Thermophysical properties and PVT relations of rubber damping materials are particularly important in the rubber processing and manufacturing industries. Based on the above contents, we carried out following works:Firstly, we performe MD simulation and experiments to analyze the correlation between the microstructure and damping properties of AO-60/NBR composites and exploring the microscopic mechanism for improving the damping properties. Secondly, critically examine the compatibility, structure, and damping properties of AO-60/NBR composites with different acrylonitrile contents. Thirdly, explore the enhancement damping and mechanical properties for the introduction of hindered phenol AO-80 small molecules into NBR/PVC blend rubber. At last, quantitative study PVT relationships and thermophysical properties (thermal expansion coefficients and isothermal compressibility) during processing of AO-60/NBR composites with different AO-60 contents.In the first part of this paper (Chapter 3), we prepared AO-60/NBR composites with different AO-60 contents. The hydrogen bonds (H-bonds), binding energy, and fractional free volume (FFV) of the AO-60/NBR composites were obtained through MD simulation. There are two kinds of H-bonds formed in the AO-60/NBR composites:O-H (AO-60)... OC (AO-60) and O-H (AO-60)...NC (NBR). The AO-60/NBR composite with an AO-60 content of 36 phr had the largest H-bonds, highest binding energy, and smallest FFV, all indicated a good compatibility between NBR and AO-60 and good damping performance of AO-60/NBR composite. Phase separation between NBR and AO-60 appeared as the AO-60 content exceeded 36 phr. The number of H-bonds can be controlled by adjusting the AO-60 contents, which will decide the optimum damping properties of AO-60/NBR composite.In the second part of this paper (Chapter 4), the effect of the acrylonitrile content in NBR on the compatibility and damping properties of AO-60/NBR was investigated by MD simulation and experimental methods. The hindered phenol AO-60 had poor compatibility with N220S with an acrylonitrile content of 41%, but had good compatibility with N230S with an acrylonitrile content of 34%. The AO-60/N230S composite had larger H-bonds and higher binding energy than the AO-60/N220S composite at the same AO-60 content, both indicating stronger interactions between N230S and AO-60 and better damping performance of AO-60/N230S.In the third part of this paper (Chapter 5), a combined study of experimental and MD simulation methods was presented for hindered phenol AO-80/nitrile-butadiene rubber/poly(vinyl chloride) (AO-80/NBR/PVC) composites with different AO-80 contents to establish the microstructure-damping property relations. MD simulation found that the AO-80/NBR/PVC composite (abbreviated as AO-80/NBVC) with an AO-80 content of 99 phr had the largest hydrogen bonds (H-bonds) and highest binding energy, indicating a good compatibility between NBR and AO-80 and good damping performance of AO-80/NBVC composites. Experimental results from SEM, DSC, and DMA were in good agreement with the MD simulation results. The tensile test results showed that the AO-80/NBVC composite with an AO-80 content of 99 phr had high tensile strength because of the strong H-bonds of the composites and the disintegration and reintegration of the H-bonds.In the fourth part of this paper (Chapter 6), the PVT work of AO-60/NBR composites with different AO-60 contents was undertaken and the PVT data were correlated with the Tait equations. Through PVT experiments, a series of thermophysical parameters, such as thermal expansion coefficient (α) and isothermal compressibility (β) can be obtained. The coefficients α and β have relation with temperature and pressure, a changes little with temperature, but decreases with increasing pressure. Moreover, β increases with increasing temperature, but decreases with increasing pressure. Therefore, more attention should be paid to the effect of pressure on the preparation and processing of the AO-60/NBR composites. The size stability of AO-60/NBR need to be improved.