Study On The Migration Of Styrene Based On Food Grade Expand-polystyrene

The toxic low-molecular-mass materials in the packaging materials, such as residualmonomers, additives and so on, can migrate from the packaging into food and be potentialcontaminants, create problems for food quality and cause adverse changes for human health. Atpresents, special migration has become one of most concerned research in the field of chemicalmigration. The residual styrene in food grade expand-polystyrene (EPS) widely used in foodpackaging may migrate from the polymer into food, which create problems for food quality.In the thesis, the migration of styrene from plastic packaging based on food gradeexpand-polystyrene was researched at different conditions. Distilled water,10%(V/V) ethanoland95%(V/V) ethanol were selected as food simulants. Experiments were carried out at varioustemperatures (25，45，65℃)from1to240h and eleven samples at different time intervals werestudied for every condition(temperature).Measurements were carried out using GasChromatography-Flame Ionization Detector with external calibration; Computer analyzedmethod was employed for modeling of the influence of three operating variables (polarity offood simulant, temperature and time) on the yield of amount of styrene migrated from food gradeexpand-polystyrene. The partition coefficient, diffusion coefficient and energy activity for themigration were analyzed based on Fick diffusion second law combined with the values ofmigration experiments，which were compared with the values through Brand model.Food simulants on the level of the affection on the amount of styrene migrated from EPSfrom high to low were95%(V/V) ethanol,10%(V/V) ethanol, distilled water. No styrene wasdetected in distilled water, except at high temperatures and long time period. The amount ofstyrene migrated from EPS in10%(V/V) ethanol and95%(V/V) ethanol were much greaterthan the values in the distilled water. Comparing with the values in the10%(V/V) ethanol, thevalues in95%(V/V) were greater. The relationship of temperatures on affection of the amount ofstyrene migrated was non-linear in the10%(V/V) ethanol and95%(V/V) ethanol.The relation of the affection of the three factors on the amount of styrene migrated wasanalyzed and it correlated the cubic modeling and the values of the modeling were in a goodagreement with the measured ones, which can predict99.92%of the valued experimented. For the hydrolysis of the model, the coefficient of the affection between the polarity of food simulantand temperature was obvious. The relation between the polarity of food simulant and time wasobvious and so was the relation between time and temperature.Combining the experiments and the theory of migration, It was assured that the migration ofstyrene from expand-polystyrene had partition behavior, which basically correlated with Fickdiffusion second law. At the view of the coefficient, the migration of styrene from expandpolystyrene correlated with Fick second law complex model more closely; In the10%(V/V)ethanol food simulant, the diffusion coefficient of the styrene in the polymer at differenttemperatures(25℃、45℃、65℃) were1.0810-12、1.1110-11、3.5810-11cm2/s and the valueof corresponding energy activity was73.2412.13kJ/mol through Fick second law complexmodel; the diffusion coefficient in95%(V/V) ethanol were5.0810-9、1.2910-8、6.8310-8cm2/s and the corresponding energy activity was51.348.57kJ/mol. The both values of energyactivity were lower than the value（91.05.00kJ/mol）through Brand model.