الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The total migration of components (additives and monomers) from plastic packaging materials into packed food simulating liquids, has been studied. Several types of plastics such as low-density polyethylene (LDPE), polystyrene (PS), polypropylene (PP) and polyvinylchloride (pYC) were used to evaluate the migration out of them into different food simulating liquids ”FSL” such as distilled water and aqueous solutions of ethyl alcohol 3%, sodium chloride 10% and acetic acid 6% at different temperatures of 15, 25, 40 and 55°C during 30 days time period. For this purpose, a new migration cell has been designed to serve as a container for contacting the systems. The evaluation of total migration was carried out depending upon the gravimetric technique with aid of spectrophotometric technique.
The influence of temperature and contacting period on the total migration of component from plastics were studied. The results for each system showed that, for all investigated systems, the rate of migrated components from plastics into food simulating liquids increased markedly with increasing temperature from 15 to 55°C. It reaches its highest values at 55°C in contacting of polymers with acetic acid (12.63, 17.24, 8.68 and 20.80 mg dissolved components / L of food simulating liquid for PYC, PP, PS and LDPE, respectively.
The migration results conftrmed that the amounts of migrated components from different types of plastics into FSL decreased in the order of LDPE > PS > PP > PYC for all FSL investigated also, it decreased in the order : acetic acid> sodium chloride> ethyl alcohol> distilled water for each polymer. Two steps take place during migration,
the fIrst step is transfer of polymer from the surface to the bulk and the second step is the intermolecular diffusion from, the interior of plastic sample to the surface.
It was found that the rate-determining step is the intermolecular diffusion. A diffusion rate parameter, K, has been defmed and used to correlate experimental data against the temperature as a variable of the system. Thereby, the diffusion rate parameter at various temperatures apart from that mentioned above can be calculated. The calculated, K, was found to increase on increasing the temperature for all contacting systems of plastic materials / FSL.
Consequently, the energies of activation was calculated for each of the previously-mentioned contact systems. These were found to be (8.1, 6.2, 5.4 and 3.1 kcal. mole-I) for systems LDPE in distilled water, ethyl alcohol, sodium chloride and acetic acid, respectively. While these were (8.7, 8.1, 4.9 and 2.9 kcal mole-I), (8.5, 7.6, 4.97 and 2.2 kcal. mole-I) and (6.9, 4.9,4.5 and 3.9 kcal. mole-I) for systems ofPS, PP and PVC in the previously mentioned food simulating liquids, respectively. The free energy of activation was obtained at various temperatures for all the above contacting systems.
The heat of activation was obtained for the previous systems witlpn the range of temperatures (15 to 55°C) and was found to increase in the order : distilled water < ethyl alcohol < sodium chloride < acetic acid for each tested polymer.
Consequently, the entropy of migration for all systems is calculated at various temperatures giving an approached negative small values, indicating more ordered systems.