No abstract

Polypropylene is one of the most widely used polymers, especially in the food packaging industry, which causes negative environmental effects. Recycling is a good option to partially solve this environmental problem. Thus, the polymer was contaminated with a cocktail to simulate the conditions of disposal and recycling following FDA guidelines. The influence of contaminants on recycled PP was analyzed by quiescent and nonquiescent crystallization. It was found that the contaminants alter the crystallization flow since longer induction times were observed for all contaminated samples. Also, the thermal behavior was performed considering that the thermogravimetric (TGA) results indicated an increase in the stability with the presence of contaminants. Therefore, a deep investigation using the induced oxidation time and induced oxidation temperature was performed. The contaminants play an important role in the crystallization process, as well as, in the degradation of the samples. Furthermore, the use of TGA and DSC as complementary techniques is fundamental to analyze this influence. Graphical Abstract

Recycling of polymers is one of the alternatives to reduce the impact of polymers presence on the environmental. However, the contaminants, defined as non-intentionally added substances, present in recycled material may migrate into food and also change its molecular structure. This work addresses the extractability/migration of contaminants from polypropylene (PP) samples into food simulants and the influence of these contaminants on the molecular structure of recycled PP. For this PP was contaminated with several substances to simulate a "worst-case" scenario and, then it was submitted to a recycling process. Extractability tests were performed by solid-phase microextraction and gas chromatography coupled to mass spectroscopy both to evaluate the presence of contaminants in the PP samples and their ability to migrate in food simulants. Additionally, molecular changes of the PP samples were evaluated by oscillatory rheometry. After washing and extrusion of the PP samples the extractability results showed considerable reductions of migrations in the food simulants and indicated, in some cases, compliance with regulations for using recycled polymer in contact with food. The residual contaminants were present in the polymer, the high temperatures and shear rates play an important role in molecular changes. Finally, the results highlight the importance of the use of rheological measurements to detect the influence of contaminants in recycled materials. Their presence result in material with different molar mass, that may be applied in different market applications.

Recycling of polymers is one of the alternatives to reduce the impact of polymers presence on the environmental. However, the contaminants, defined as non-intentionally added substances, present in recycled material may migrate into food and also change its molecular structure. This work addresses the extractability/migration of contaminants from polypropylene (PP) samples into food simulants and the influence of these contaminants on the molecular structure of recycled PP. For this PP was contaminated with several substances to simulate a “worst-case” scenario and, then it was submitted to a recycling process. Extractability tests were performed by solid-phase microextraction and gas chromatography coupled to mass spectroscopy both to evaluate the presence of contaminants in the PP samples and their ability to migrate in food simulants. Additionally, molecular changes of the PP samples were evaluated by oscillatory rheometry. After washing and extrusion of the PP samples the extractability results showed considerable reductions of migrations in the food simulants and indicated, in some cases, compliance with regulations for using recycled polymer in contact with food. The residual contaminants were present in the polymer, the high temperatures and shear rates play an important role in molecular changes. Finally, the results highlight the importance of the use of rheological measurements to detect the influence of contaminants in recycled materials. Their presence result in material with different molar mass, that may be applied in different market applications.