Migration Of Nano-components In Nano-metal/metal Oxide-polyolefin Films

Nano-copper,nano-silver,nano-zinc oxide and nano-titanium dioxide have excellent antibacterial properties,and they are combined with polyolefins such as Low Density Polyethylene and polypropylene to improve the corresponding food contact materials.However,the migration of nano-components to food may cause food safety problems.For this purpose,the migration of nano-components in nanometal/metal oxide-polyolefin films is studied:(1)According to the experiments of our group,the diffusion coefficients of nano-copper and nano-silver are calculated by Crank model.The influencing factors are studied.The increase of temperature promotes the migration of nano-components.The relationship between diffusion coefficient and temperature is in accordance with Arrhenius formula.Among polypropylene,nano-zinc oxide and nano-copper have the largest diffusion coefficient in homopolymer of polypropylene.The concentration of the nano-component affects its diffusion coefficient.The difference in solubility parameters among food simulants,nano-components and polyolefins affects the migration of nano-components.(2)Based on the experiments of our group,the migration of nano-components in the films is simulated by AKTS-SML software,and the compatibility of migration with Fick's second law is verified.The migration simulation of nano-copper in nanocopper/polyolefin to acetic acid with a mass fraction of 3% basically conforms to the above law.After adding a coupling agent to the films,the simulated values of the migration amount of the nano-copper differ greatly from the experimental values.The AKTS-SML software is not suitable for simulating the migration of unbalanced and migrated quantities near the software's computational limits.(3)The molecular dynamics simulation of nano-copper diffusion in LDPE or PP is carried out.The mean square displacement,diffusion coefficient and free volume of nano-copper are analyzed.The mean square displacement and diffusion coefficient increase with increasing temperature.The free volume fraction decreases as the probe radius increases.(4)Based on the experiments of our group,the partition coefficients of nanometal/metal oxides between films and food simulant in the experiment are calculated,and the partition coefficients are fitted by Scatchard-Hildebrand theory.The partition coefficients of nano-copper/nano-silver between polyolefin and 3% acetic acid decrease with increasing temperature.The migration amount of nano-components to 3% acetic acid is greater than that to other food simulants.Among polyolefins with different structures,the distribution coefficient of nano-copper between random copolymer of polypropylene and 3% acetic acid is the largest.For low density polyethylene and polypropylene,the greater the molar volume of the nanocomponent is,the higher the accuracy of the results obtained by the Scatchard-Hildebrand model will be.