Comparison of Different Extrusion Processes for Cleaning the Recycled Polypropylene Removing Volatile and Non-Volatile Contaminants

Abstract

Many studies have been carried out in order to enable the use of recycled polymers in food packaging. The main problem is the presence of residual contaminants in recycled plastic, because it could pose a risk to public health when in contact with food. Our purpose is to evaluate different types of mechanical recycling in order to decontaminate the polypropylene. Firstly, pellets of polypropylene were contaminated, following the protocol recommended by the FDA. The pellets were subsequently recovered (washed and dried) and the samples were submitted to different extrusion processes. In order to evaluate the decontamination degree of the samples that went through each type of mechanical recycling, extractability tests were performed under different conditions of time, temperature and using different food simulants. The surrogates that migrated (suffered forced migration) were quantified using chromatographic techniques. The results showed that the decontamination degree of the samples changed with the different methods of extrusion applied. They also showed that conditions of time, temperature and different food simulants actually influenced the extraction of the surrogates.