Research On The Degradation Behavior Of Magnesium Reinforce Polylactic Acid Composite

Polylactic acid/magnesium alloy composite is a novel biomaterial with good biocompatibility and biodegradability.The degradation performance is the basis of the clinical application.However,the degradation mechanism of polylactic acid and the corrosion mechanism of magnesium alloys are very complicated.Numerous factors can influence the degradation and the corrosion,moreover,polylactic acid degradation and magnesium alloy corrosion may affect each other.It is difficult to fully analyze the degradation kinetics mechanism of composite through simple experimental research.In this paper,the degradation behaviors of polylactic acid/magnesium alloy composites are first studied through degradation experiments,then the degradation kinetics of polylactic acid,magnesium alloys and composites are simulated by cellular automata method.Polylactic acid/magnesium alloy composites were prepared by adding different volume fractions of AZ31 B magnesium alloy wire.The effects of magnesium alloy wire volume fraction on the mechanical properties and in vitro degradation behaviors of the composites were investigated.It has been found that the directional strengthening of magnesium alloy wire can effectively improve the bending strength of the composite.The bending strengths of the 10vol% and 20vol% magnesium alloy wire composites are increased by 23.6% and 33.9% compared with polylactic acid sample,respectively;the addition of the magnesium alloy wire can effectively neutralize the acidic degradation products of polylactic acid and reduce the degradation rate.Coarse-grained Monte Carlo algorithm with fixed time step and finite difference method were used to simulate the processes of chain scission,recrystallization,oligomer formation and diffusion,and a two-dimensional cellular automata model was designed to simulate the degradation of polylactic acid.Using the model,the effect of scission way,autocatalytic mechanism,crystallinity,diffusion process and material size on the degradation of polylactic acid were studied,and it was proved that both random scission and end scission existed in the degradation process of polylactic acid.A method for judging the accuracy of the model using the root mean square error Re was presented.The high degree of agreement between the simulation results and the experimental results proved the feasibility of the model for polylactic acid degradation simulation.According to the new magnesium alloy corrosion kinetics equation,a two-dimensional cellular automata model of magnesium alloy corrosion was established,the effects of corrosion modes and corrosion kinetic parameters on the corrosion of magnesium alloys were also studied.The simulation results were in good agreement with the experimental results in the literature.On this basis,a cellular automaton model for degradation of polylactic acid/magnesium alloy composites was proposed,the feasibility of the model to simulate the degradation behavior of polylactic acid/magnesium alloy composites were confirmed.