Use of functional barriers

It is generally known that only a very limited number of packaging materials such as glass or metal provide absolute protection properties concerning the penetration of chemical compounds from layers behind or from the environment. In the case of multi-layers with plastics materials as functional barriers there occurs, in most cases to a certain extent, an unavoidable mass transfer from the plastics layers into the product. This must be understood as a functional quantity which, however, must comply with food regulations. Therefore it is necessary firstly to understand functional barrier characteristics and mechanisms and, secondly, to define the functional barrier efficiency in relation to food safety and to establish appropriate test methods. This is especially important with those food packaging applications where recycled plastics are covered by plastics functional barriers. 

Over the last decade numerous publications have dealt with the functional barrier concept from different points of view and with different scientific 

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 

As a consequence, three principally different situations for a functional barrier packaging system can be assumed as depicted in Fig. 9.2. The corresponding kinetic migration characteristics are outlined in Fig. 9.3 which categorises the kinetic migration behaviour possibilities for a migrant at time t = 0 (for instance the time of package fill) into three typical cases  

Clean functional barrier full lag time of the functional barrier takes effect. 

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