| Polymer nanocomposites(PNCs)are now used in a wide range of applications.During processing and application,it can improve its various properties by adding fillers.In this thesis,molecular dynamics simulation was used to investigate the viscoelasticity of PNCs respectively filled with spherical nanofillers(nanoparticles),rod nanofillers(nanorods)and sheet nanofillers(nanosheets),comparing the effects of filler shape and filler size on the energy storage modulus,loss modulus,and Payne effect.It was found that among the three fillers,the nanorods had the most prominent ability to enhance the energy storage modulus of PNCs at low strain,followed by the nanosheets,and the nanoparticles had the weakest ability;the effects of the three different shapes of fillers on the loss modulus and Payne effect of the composite systems were similar to the results of energy storage modulus.Comparing the effect of filler size,it can be found that the increase of filler size improves the energy storage modulus of the PNCs and has little effect on the Payne effect.Meanwhile,this thesis has explored the mechanism of modulus enhancement of the PNCs systems respectively filled with these different shape fillers and different size fillers above.The results of the simulated computational analysis show that the main source of modulus enhancement of PNCs respectively filled with nanorods and nanosheets changes with the increasing volume fraction of the filler: from the Rouse kinetics of the polymer chains to the binding force of the filler on the polymer chains,and finally to the filler network.In contrast,increasing the filler size makes the Rouse dynamics region and chain confinement region narrower and the permeation threshold lower.However,the source of modulus enhancement for the PNCs system filled with nanoparticles is mainly the Rouse kinetics of the polymer chains,and the modulus enhancement of the composites is consistent with the above mechanism only at a high interface degree of nanoparticles. |
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