- Practical Guide -
Page 68 of 153
For polyamide only few data are available both for diffusion coefficients and migration.
Furthermore, the relative humidity can strongly influence the mechanism of the transfer.
Pending new data the value reported in Table 3.4.1 can be a first tool to estimate migration.
Ranges of parameters for the applicability of the migration model for PA 6,6.
For PA 6,6 the actual values of A'
t from Eq. (5) were determined empirically using
migration data from well defined migration experiments reported in recent years by
internationally recognized laboratories /1, 2/. Using these values of A'
t (see table 3.4.2)
in Eqs. (4) and (5) results in "upper limit" diffusion coefficients, D
, which, introduced in
Eq. (2), lead to overestimations (in most cases largely) of the migration database values.
Table 3.4.2: Parameters for PA
Besides the polymers described above other packaging polymers or polymer modifications
can be found on the market and, in addition, new polymer developments may be developed.
In principal, migration modelling is also applicable to those polymers for migrants listed in
Annex A or other organic chemical substances. In those cases, the procedure described in
Annex B can be applied to establish experimentally the relationship between the initial
concentration of a migrant in a polymer and its specific migration or with other words the
basic diffusivity of the polymer expressed as the polymer specific A
Procedures, practical applications and examples
For migration modelling as described above corresponding home made computer programs
may be established and applied. For conveniency reasons, it should be noted that a
specifically tailored and userfriendly computer program is available on the market
(MIGRATEST Lite 2001, FABES GmbH Munich, Germany) or can be freely downloaded
from the internet (SMEWISE, INRA Reims, France at: