Molecular Simulation Study On Crystallization And Deformation Behavior Of Polymer And Its Nanocomposites Systems

Polymer materials have attracted extensive attention from academic and industrial circles due to their excellent performance and good processability.Their related industries have gradually become an important pillar of the national economy.In actual production and life,polymer materials are mostly in a semi-crystalline state,and their properties are closely related to the crystal morphology.Nanoparticles affects the crystallization behavior of the polymer and effectively improves the basic properties of the polymer material.Understanding the formation mechanism of the microstructure of polymers and their composite systems at the molecular level is an important basis for realizing the regulation of polymer structure properties,improving material properties,and guiding the production process.The use of traditional experimental methods to study the evolution of polymer nanostructures is costly,time consuming,and laborious.And the limitations of experimental conditions and the contingency of experimental results are prone to errors.Computer simulation technology makes up for the shortcomings of traditional experimental methods,and helps to understand the mechanism of polymer microstructure and performance change from different scales.Based on the molecular dynamics method,this paper systematically studied the crystallization behavior and deformation mechanical behavior of polymers and its nanocomposites.Monodisperse and polydisperse polymer systems were constructed based on Monte Carlo random self-avoiding walking method.The coarse grained molecular dynamics method was used to study the crystallization behavior of the polymer under isothermal and tensile induction conditions.The effects of crystallization temperature,molecular chain dispersibility,stretching temperature and stretching rate on the crystallization behavior of the polymer and its variation were analyzed.The crystallization driving force,microscopic conformational transformation and condensed structure of the polymer crystallization process were investigated.The semi-crystalline structure of the polymer and its nanocomposite system was obtained by simulation.Through analysis of the system's entanglement parameter.conformational distribution,interface orientation,crystal grain thickness and crystallinity,the effects of graphene as a nanofiller on the crystallization behavior were investigated.The mechanism of graphene promoting the crystallization of the polymer was revealed,and two nucleation mechanisms existed in the crystallization process of the composite system.At the same time,the influence of molecular chain length on the crystallization behavior of the nanocomposite system was analyzed.It was found that the crystallinity and the average thickness of the crystal region of the short chain system were larger than those of the long chain system.The tensile deformation behavior of polymer system and its nanocomposite system were studied.The evolution process of polymer entanglement,energy,conformation distribution and orientation during deformation was investigated.The deformation mechanical behavior of graphene on semi-crystalline polymer matrix was analyzed.The influence of the graphene for tensile deformation behavior of the polymer matrix and the influence of the aggregation state of the polymer matrix on the tensile deformation behavior of the composite system were analyzed.The mechanical strengthening mechanism of the nano-polymer composite was revealed.