The results of a research project (EU AIR Research Programme CT94-1025) aimed to introduce control of migration into good manufacturing practice and into enforcement work are reported. Representative polymer classes were defined on the basis of chemical structure, technological function, migration behaviour and market share. These classes were characterized by analytical methods. Analytical techniques were investigated for identification of potential migrants. High-temperature gas chromatography was shown to be a powerful method and 1H-magnetic resonance provided a convenient fingerprint of plastic materials. Volatile compounds were characterized by headspace techniques, where it was shown to be essential to differentiate volatile compounds desorbed from those generated during the thermal desorption itself. For metal trace analysis, microwave mineralization followed by atomic absorption was employed. These different techniques were introduced into a systematic testing scheme that is envisaged as being suitable both for industrial control and for enforcement laboratories. Guidelines will be proposed in the second part of this paper.

Polypropylene-g-polyacrylic acid copolymers were prepared by graft polymerization of acrylic acid onto polypropylene (PP) using electron beam preirradiation method. Samples with various graft levels were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The physical structure of grafted PP was significantly affected by the graft content. While XPS revealed an increase in the oxygen content on the PP surface, the crystallinity of the graft copolymer decreased with an increase in the degree of grafting. The heat of fusion as obtained from DSC decreased with the increase in the degree of grafting and was ascribed to the dilution of inherent crystallinity by the incorporation of amorphous polyacrylic acid grafted chains. The thermal stability of graft copolymers was also enhanced as compared to the virgin PP.

No abstract

The penetration of olive oil into polypropylene was studied in order to allow a complete modellization of food and packaging interactions. Oil concentration profiles through polypropylene food trays were determined by FTIR-microscopy measurements along the thickness at various times. Calculations of the relevant parameters characterizing Fickian diffusion, namely constant diffusivity, coefficient of convective mass transport on the surface and concentration at equilibrium were carried out. This way of working has proven to be considerably shorter and more accurate than the method consisting of recording the global absorbance of the substance absorbed, especially when the amount of diffusing fat is low. Major conclusions are: that absorption of olive oil is strongly influenced by convection; the diffusion coefficient of olive oil in polypropylene is constant. Possible consequences to simplify global migration testing are discussed.

No abstract