Molecular Dynamics Study On Mechanical Properties And Photodegradation Mechanism Of Polyethylene Plastics Modified By Nanoparticles Molecular

The excellent chemical stability,toughness,and ease of processing have made polyethylene materials widely used in various industrial and daily life applications.However,their biodegradability poses a significant threat to the environment,making their degradation a pressing research topic for scholars.Photodegradation has emerged as a popular method for degrading polyethylene,owing to its low production cost and straightforward process.Incorporating photocatalysts into the polyethylene matrix material can render it photodegradable,with titanium dioxide being the most commonly used photocatalyst for this purpose.Molecular dynamics simulation is a valuable tool for investigating material properties and degradation reactions by conducting simulation experiments at the microscopic level to elucidate mechanisms that cannot be directly observed in experiments.This paper utilizes molecular dynamics simulation to investigate the following research areas:The stability of polyethylene-titanium dioxide(PE-TiO2)composites prior to stretching was investigated using LAMMPS through analyses of their MSD and glass transition temperature.Additionally,the mechanical behavior of the composites under uniaxial tensile loading,the effects of varying filler concentrations,and the interaction mechanism between titanium dioxide particles and polyethylene chains were simulated.The results indicate that the addition of titanium dioxide enhances the performance of polyethylene materials,and the thermodynamic stability is improved within a certain concentration range.Uniaxial tensile simulations revealed that the addition of titanium dioxide increased both the strength limit and fracture limit,indicating that titanium dioxide contributes to improving the mechanical properties of the material.Furthermore,the mechanical properties of the composites were found to be enhanced with increasing titanium dioxide concentration.The filler particles improve the overall mechanical properties of the material by improving the peripheral chain distribution and energy action stage.To investigate the photodegradation of polyethylene using titanium dioxide as a photocatalyst,a two-step degradation process was simulated.The first step involved the catalysis of hydroxyl radical formation by water molecules on the surface of titanium dioxide Nanoparticles,while the second step involved the breaking of polyethylene chains through the reaction of hydroxyl radicals with polyethylene.The simulation of hydroxyl radical formation on the surface of titanium dioxide revealed that the reaction occurred on the surface of the catalyst,where water molecules broke hydrogen-oxygen bonds to form hydroxyl groups that were then released into the system to form hydroxyl radicals.Furthermore.the simulation showed that water molecules tended to form clusters during the adsorption process,and reducing cluster formation was found to be crucial for increasing hydroxyl radical yield.Observation of the hydroxyl radical mechanism on the surface of polyethylene showed that these highly reactive oxide species played a crucial role in initiating the chain reaction.Hydroxyl radicals absorbed hydrogen to form water,and in the process,C-C bonds on the polyethylene chains broke to form alkyl radicals.These radicals could either undergo β-break or continue reacting with hydroxyl radicals to form alkoxy groups.The breaking of C-C bonds resulted in the production of different C0-C4+small molecule products,with ethylene and vinyl being the most significant.The simulation also revealed that while an increase in hydroxyl groups was beneficial to the degradation process,a higher concentration of water molecules had a detrimental effect on the process.