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Evaluation of a Mathematical Model of Dioctyl Phthalate Plasticizer Migration from PVC Discs into Colza Oil

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Results of long time tests are given for migration of dioctyl phthalate (OOP) from solid PVC discs into well-stirred colza oil. The following factors were examined: time, plasticization level (from 20 to 50 wt%), and temperature (30 and 50aC). The use of labelled OOP and radioactivity measurements in conjunction with weight loss give quantitative information on the mass exchanged (plasticizer migration and colza oil penetration) and lead to OOP concentration profiles that are developed through the bulk of polymer during the process. Mathematical model investigated in this study takes into account the following conditions: (1) the concentration of colza oil in the polymer matrix was neglected; (2) the diffusion in transient conditions through the PVC mass with OOP concentration-dependent diffusivity was considered. Statistical analysis shows that this self-consistent model is able to reproduce, to a good approximation for the OOP, the concentration profiles in the polymer, and the kinetics of transfer into the oil.

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