Experimental Study And Molecular Dynamics Simulations Of Diffusion Of Bisphenol Componds From Inside Coating Of Metal Food Cans

Food packaging materials contacted with food directly,effected the safety of food and the health of consumers as a protection of "clothes".Metal cans packaging is popular with consumers because of its good performance.But due to processing reasons(crosslinking insufficient)and the influence of the external environment,some monomeric substances,processing agents and other small molecules can spread into the food,and effected the food safety.It is of important value and prospect that the experimental study on bisphenol compounds in metal cans inside coating epoxy resin under different conditions was established,the migration theory was stated from the molecular level through building epoxy crosslinking model by molecular simulation software.extraction method of BPA,BFDGE,BADGEin food simulants had been established,including highperformanceliquidchromatography-fluorescence detection(HPLC-FD)and Waters XTerra C18(250 mm×4.6 mm,5?m)column.The validation data showed good linear relationship,the linear ranges were 0.01~2?g/m L,regression coefficients(R2)> 0.9993 for all analytes.The metal cans had been soaked in 20% ethanol,n-hexane,4% acetic acid,distilled water as food simulation under different temperature.The migration amount of bisphenol compounds was determined at different times.The results show that the main migration process of the b isphenol compounds was at the former 48 h.Based on the mathematical model of migration,MF,t/MP,0 as ordinate and t(s)as abscissa,to fit the important parameter of diffusion coefficient DP.Regression coefficients R2 was between 0.8233~0.9722.Comparing the diffusion coefficient under different soaking condition,the conclusions show that:(1)With the increase of temperature,diffusion coefficients of three kinds of bisphenol compounds increased.(2)At the same temperature,the diffusion coefficient in different food simulation was 20% ethyl alcohol> n-hexane > 4% acetic acid > distilled water.So metal cans packaging materials were in a higher risk contacted with alcohol food and fat food;in a less risk used for alcohol food and water.(3)At the same conditions,the diffusion coefficient of three kinds of bisphenol compounds was BPA > BFDGE > BADGE.The epoxy resin crosslinking curing model(DGEBA/IPD)was built by molecular dynamics simulation software(material studios),got the mean square displacement(MSD),diffusion coefficient,free volume fraction and the diffusion mechanism through dynamics simulation under different temperature.The diffusion theory of small molecule s in epoxy resin was revealed from the microscopic level.The results show that:(1)The curve of mean square displacement changed with time at the different temperature shew good linear,correlation coefficient R2 was between 0.7958~0.9269;(2)Compared the diffusion coefficient at different temperature between simulated values and experimental values,the results shew that the change trend of the simulated values was same as the experimental values,although the simulated values were greater than the experimental values,and explained its reason.(3)Compared the free volume fraction at different simulation temperatures and different probe molecular radius,the results shew that with the simulation temperature increasing,the free volume fraction was almost the same;with the increase of probe molecular radius,the free volume radius decreased significantly.Explained the diffusion mechanism from the aspects of free volume.(4)Recorded the location of diffusion molecules at different phase though simulatio n software,and compared with gas molecular diffusion,the results shew that the diffusion of bisphenol compounds was slow peristalsis,rather than jump diffusion.