Multiscale Simulation Of Compatibility And Mechanical Properties Of Polylactic Acid Blends

With the development of computer technology,the application of computer simulation in the field of materials has become more and more extensive,which can explain the microscopic principles and essence of experiments.Although polylactic acid(PLA)has good degradability and biocompatibility,the mechanical properties and mechanical properties of PLA are poor.Therefore,PLA needs to be modified appropriately before it can be used in actual production.This article simulates the blends of PLA and several modifiers,and the results show that the compatibility of PLA and Amylose blends is better than others.Further,molecular dynamics(MD)and mesoscopic dynamics(Meso Dyn)are used to simulates the structure and properties of PLA/Amylose blends with different mass ratios,and simulates the structure and properties of MAH grafted PLA/Amylose blends.(1)Perform blending simulation of PLA with some common modifiers(Amylose,polyethylene glycol(PEG),dioctyl phthalate(DOP),epoxy soybean oil(ESO),polycaprolactone(PCL),tributyl citrate(ATBC)),and simulate the compatibility of the blend.The analysis of the binding energy between the blend shows that the more similar the binding energy between the blend and the modifier,the better the compatibility.The simulation obtained the relationship between cohesive energy density,mixing energy,interaction parameter ? and simulated temperature.It is found that as the temperature increases,the interaction parameter of the blend material gradually decreases and gradually tends to an equilibrium value,but the mixing energy first increases and then decreases.The simulation results show that the consistency of the binding energy of the blended components of PLA and Amylose is better,indicating that their compatibility is better.(2)Since the various properties of composite materials mainly depend on the compatibility between materials,first use the Amorphous cell module to establish an amorphous model of PLA/Amylose blends with different mass ratios,and use MD to simulate the cohesive energy density(CED),solubility parameter(?),Flory-Huggins interaction parameter(?)and mechanical properties of PLA/Amylose blends.The research results show that when the mass ratio of PLA/Amylose blend is 70/30,the simulated ?is slightly smaller than ?c.Therefore,the PLA/Amylose under this mass ratio has excellent compatibility,and the ? of the other blends is greater than ?c.The simulation of 500 K to 100 K gradual cooling of the blend system shows that with the increase of temperature,the volume,bond energy and bond angle energy of the blend system gradually increase,but the volume and torsion energy of the system have turning points(ie glass transition phenomenon)as the temperature increases.Only the blend with a mass ratio of 70/30 has only one glass transition point that is the glass transition temperature(Tg),it indicating the PLA/Amylose with a ratio of70/30 has a certain degree of compatibility.The simulation of the mechanical properties of the blend shows that as the proportion of PLA components in the blend increases,the various mechanical properties gradually decrease,reaching the lowest value when the mass ratio is70/30.Calculate the input parameters of Meso Dyn simulation according to the interaction parameters calculated by MD,and use Meso Dyn to simulate PLA/Amylose blends at the mesoscopic scale.Then conduct mesoscopic morphology analysis on the blends of various mass ratios,it is found that the mixed form gradually changed from "sea-island" structure to a dual-connected structure,and then became a "sea-island" structure again.Through analysis the simulation results,it is found that the PLA/Amylose blend with a weight ratio of 70/30 has good compatibility.(3)Graft maleic anhydride(MAH)on PLA according to different grafting rates,blend it with Amylose at a mass ratio of 70/30,and use MD to simulate the grafting rate to determine the CED and mechanical properties of the blend.The analysis results show that as the grafting rate in the blend increases,the CED and various module of the MAH-PLA/Amylose blend gradually increase,while the compressibility gradually decreases,indicating that the grafting of maleic anhydride PLA can effectively improve the mechanical properties of its blend with Amylose.