PROSPECTS FOR APPLICATION OF POSTCONSUMER USED PLASTICS IN FOOD-PACKAGING

The two most widely used polymers in packaging in recent years are pol yethylene terephthalate (PET) and polyethylene (PE). The biggest fract ions of these polymers are not re-utilized, in spite of the fact that they possess excellent properties even after their first application. The ban on using recycled polymers in food packaging applications and the lack of good value outlets for these materials causes them to end up in landfills. The high cost nylon, used in packaging primarily as h igh gas barrier laminates with PE, also finds its way to landfills. In this case, the reason is the difficulty of recycling different polyme rs that are incompatible. Thus, the Municipal Solid Waste (MSW) stream transferred to landfills contains many plastic packages. These packag es are being blamed as a major pollutant of the environment in spite o f the fact that all plastics contribute only a small percentage to the weight of the garbage in landfills. If proper and cost effective appl ications for the recycled polymers could be developed, the waste relat ed to their disposal could be limited. In addition, the contribution o f plastic packages to the environmental problem could be diminished, I n the present paper, the possibility of sandwiching a contaminated PET layer between two layers of the virgin material was studied. The aim of the study was to determine whether such an operation could lower th e migration level of contaminants from a multilayer structure (contain ing a recycled layer of PET) to values below the limits required by re gulatory agencies. The diffusion coefficients (required to determine m igration) of four organic liquids in PET were determined. As a result of the sandwiching operation, the amount of pollutant (toluene) migrat ing into the food simulant was reduced by two orders of magnitude, The properties of PE/nylon blends were also studied, It was found that th e high gas barrier properties of nylon are preserved in the blend when proper processing conditions ave used. Therefore, the recycled materi al could be used as a centre layer in a multilayer structure providing good gas barrier properties to this structure.