Experimental And Molecular Simulation Study On The Migration Mechanisms Of Phthalate Kind Plasticizers From PVDC Matrix To Food Simulation

For the processing performance of the resin and the use performance of plastic packaging materials,a variety of additives are usually added to the formula,and plasticizer is one of them.There is no chemical bond between the plasticizer molecule and the resin polymer chain,which easily causes the migration of the plasticizer molecule from the matrix to the packaged object during the use of plastic products.When the plasticizer are phthalates(PAEs)and the packaged object is food,the toxic PAEs may migrate into the food under certain conditions.This migration will cause food pollution,endanger the health of consumers,and cause potential safety hazards.Food safety is closely related to people’s health and life safety,and is the cornerstone of national security,social stability,and people’s happiness.Therefore,it is of great significance to explore the migration process of plasticizers when plastic packaging materials come into contact with food under various conditions.At the same time,the analysis of migration influencing factors and migration mechanism can provide basic theoretical basis and help for the selection of food packaging material additives.Using a combination of experiments and molecular simulations,this study investigates the diffusion of three phthalate plasticizers(DMP,DBP,DCHP)in polyvinylidene chloride(PVDC)and their migration mechanism.Firstly,the diffusion coefficient of PAEs in the migration process was obtained through migration experiments,and the influence of macroscopic factors on migration was analyzed.Based on this,the PVDC/PAEs model and the PVDC/PAEs/food simulant model were constructed respectively,and the influence of internal structural factors and external factors on the migration of PAEs was analyzed from the microscopic perspective of the molecular level.The specific research includes the following two parts:(1)By gas chromatography-mass spectrometry(GC-MS),the migration of three PAEs plasticizers in the PVDC film over time was studied,and the change of migration in different food simulants was analyzed,and the diffusion coefficient of PAEs was obtained experimentally.The data shows that from the perspective of the structural characteristics of the migrating molecules,molecules with small molecular weights are more likely to cause migration.The diffusion coefficient of DMP in n-hexane is 2.97 times that of DCHP.The order of migration rates of the three plasticizers is: DMP > DBP > DCHP.From the perspective of food simulants,the order of mobility is: n-hexane > 65% ethanol solution > 4% acetic acid solution ≈ water.(2)A PVDC/PAEs model and a PVDC/PAEs/food simulant model were constructed for molecular dynamics(MD)simulation.The results showed that the plasticizer migration process was affected by multiple internal and external factors.Internal factors such as diffusion activation energy,interaction energy and free volume fraction will comprehensively affect the diffusion of plasticizers.The diffusion activation energy of DCHP in PVDC is 1.92 times and 1.35 times that of DMP and DBP,respectively.The interaction between DCHP and PVDC The energy is 1.65 times and 1.22 times of the interaction energy between DMP and DBP and PVDC,respectively,the high diffusion activation energy of DCHP in PVDC,the strong binding energy of DCHP and PVDC,the small free volume fraction of the system and the large size of DCHP molecules,etc.There are many reasons for the low mobility of DCHP in PVDC.External factors include temperature and food type,etc.The simulation results show that the diffusion coefficient of DCHP in n-hexane at 323 K is 3.21 and1.38 times that of 273 K and 298 K,respectively,and 3.19 times that of DCHP in water at the same temperature of 323 K.The results show that for alcohol,fat and food packaging used in high-temperature environments,the selection and addition of packaging materials and additives should be more strictly controlled.This topic verified the feasibility of molecular simulation as a theoretical method for plasticizer migration analysis.This research model has a good application prospect as a migration theory and quantitative evaluation method for additives.