Modeling of Additive Diffusion Coefficients in Polyolefins

Overestimated diffusion coefficients for the prediction of worst case migration from PET: application to recycled PET and to functional barriers assessment

“…The general trend is that diffusion coefficients decrease when molecular weight increases. 2 Two zones are observed in Figure 1: the lowest molecular weight compounds (80 < M < 130 g/ mol) (dimethyl sulphoxide, toluene, phenol, 2,4-pentanedione and chlorobenzene; entries 1-5 in Table 1) have close diffusion coefficients in both virgin PET and PET plasticized by ethanol, and a plateau is shown. Log D then strongly decreases with M > 130 g/mol.…”

“…In a first pessimistic case, we consider pollution by very fast diffusing molecules, all with a very high initial diffusion coefficient D* PET/PET = 7.7 ¥ 10 -14 cm 2 /s (in virgin PET) [from equation (2)]. This diffusion coefficient increases to the value obtained in contact with water [D* PET/aqu = 2 ¥ 10 -13 cm 2 /s, from equation (4)].…”

“…1,2 Considering this linear approximation (for low conversion yields) of migration kinetics, the reference curve of Figure 5 can be used to calculate maximum acceptable initial concentrations, considering a contact time other than 1 year. Overestimated migrations of potential pollutants into aqueous media after 1 year at 40°C have been simulated for direct contact with recycled PET and for contact with a functional barrier.…”

“…However, the very large number of available data gave confidence for equation (1). [1][2][3] In a second step, predicted and experimental migration values were compared, which allowed a readjustment of the A, B and C coefficients.…”

New Insights in Polymer-Biofuels Interaction

“…They were developed for predicting migration of chemicals from food packaging. They work especially well for linear molecules [34]. An example of these models is the following one: The parameter values determined by Begley et al [35] for some polymers are listed in Table 5.…”