Contamination functional barrier

Contamination functional barrier depending on the degree of contamination of the functional barrier, only reduced lag time available. 

Fully contaminated functional barrier direct contact and no lag time. 

One approach to reduce the contaminant levels consists in reusing the wasted plastic as the core of the new material. Residues of pesticides or harmful contaminants may limit recycling of plastics as a result of their potential toxicity. Utilisation of post-consumer plastics for pharmaceutical or food-contact applications is forbidden, and multilayer food packaging materials manufactured using functional barriers are subjected to strict regulations [9, 40, 41]. 

In order to guarantee the suitability of the recyclate for direct food-con-tact or multilayer applications, in the presence of appropriate functional barriers, identification and quantification of low molecular weight contaminants in recycled resins becomes necessary. 

In chapter 7, section 7.2.8 an example of permeation through a functional barrier is described. Three-layered coextruded PET films were produced in which the core layer (P) was contaminated with chlorobenzene and the outer barrier layers (B) were made with virgin material. During the coextrusion process a partial contamination of the virgin layer occurred. The symmetrical structure of this film leads to a simplified treatment of it as a two layer laminate with the thickness d = a + b = 160 + 40 = 200 pm. For the modeling of this problem with numerical mathematics all parameters given in Section 7.2.8 are used. 

Franz R, Huber M and Piringer O G, 1994, Testing and evaluation of recycled plastics for food packaging use - possible migration through a functional barrier. Food Additives and Contaminants 1994, 11 (4), 479-496. 

Laoubi S and Vergnaud J M, 1995, Process of Contaminant Transfer Through a Food Package Made of a Recycled Film and a Functional Barrier. Packaging Technology and Science 8, 97-110. 

Laoubi S and Vergnaud J M, 1996, Theoretical treatment of pollutant transfer in a finite volume of food from a polymer packaging made of a recycled film and a functional barrier. Food Additives and Contaminants 13 (3), 293-306. 

Taking co-extrusion temperatures up to 280 °C into account, it can be estimated, in relation to the polymer type and thickness, that middle layer contaminants are penetrating the functional barrier layer partially or completely within a time range of seconds down to fractions of one second. As a consequence, more or less significant contamination of a virgin functional barrier layer is likely to occur during manufacture. This compromises the... 

Fig. 9.2 Possible levels of contamination of functional barrier packaging structures at time of package fill (t = 0).

The results of these comprehensive studies have been recently published in two papers To study functional barrier contamination effects taking place during manufacture when multi-layers are produced at high temperatures, and when the molten polymer layers are put in contact together, methods were elaborated to determine diffusion coefficients in molten polymers. It... 

R. FRANZ, M. HUBER, o. G. PIRINGER, Presentation and experimental verification of a physico-mathematical model describing the migration across functional barrier layers into foodstuffs. Food Additives and Contaminants, 1997, 14, 627-640. 

R. FRANZ, Programme on the recyclability of food packaging materials with respect to food safety considerations - Polyethylene terephthalate (PET), paper board and plastics covered by functional barriers. Food Additives and Contaminants, 2002, 19(snpplement), 93-110. 

J. SIMAL-GANDARA, M. SARRIA-VIDAL, R. RIJK, Tests of potential functional barriers for laminated multi-layer food packages. Part II Medium molecular weight permeants. Food Additives and Contaminants, 2000, 17(9), 815-819. 

P. DOLE, A. E. FEIGENBAUM, C. DE LA CRUZ, S. PASTORELLI, P. PASEIRO, T. HANKEMEIER, Y. VOULZATIS, s. AUCEJO, P. SAILLARD, c. PAPASPYRIDES, Typical diffusion behaviour in packaging polymers - Application to functional barriers. Food Additives and Contaminants, 2006, 23(2), 202-211. 

The amount of contaminant transferred into the functional barrier at time t is obtained by integrating the concentration with respect to the space between the abscissa H and L. This amount is expressed as a fraction of the amount of contaminant initially found in the recycled polymer layer ... 

As the functional barrier will be in contact with the food, it is of interest to get good knowledge of the concentration of contaminant on its external surface defined by x = L. 

The results of interest for determining the efficiency of the functional barrier on the transfer of contaminant include the following ... 

The kinetics of transfer of the diffusing substance (pollutant or contaminant) from the recycled polymer layer into the functional barrier are drawn in Figure 2.25, by using dimensionless numbers for the amount of substance transferred M/Mjn and for the time D-t/L. ... 

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