Avaliação dos tipos de processamento na descontaminação e na degradação do polipropileno reciclado / Evaluation of types of processing in the decontamination and degradation of recycled polypropylene

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

15/12/2010

RESUMO

Polypropylene is one of the most used polymers worldwide, especially by the disposable packaging industry, causing serious environmental problems. Despite the fact that recycling this polymer has become common in Brazil due to its growing market, there are still some restrictions regarding its use in direct-contact food packaging. Therefore, in order to evaluate the viability to use the recycled polymer as direct-contact food packaging, the pellets of PP were contaminated simulating the post-consumed material. Thus, the protocol of the Food and Drug Administration (FDA) was applied on the project and the following contaminants were used: benzophenone, chloroform, tetracosane and toluene. Some samples were recovered (washed and dried). The same samples were processed by three types of extrusion: single screw extrusion, co-rotating double-screw forced degassing extrusion and single-screw cascade extrusion. Initially, in order to simulate the forced migration of the contaminants to the food, the extraction tests were performed in different conditions. For this, all samples were grinded with the purpose of improving the extraction efficiency. The same samples were kept in three situations: at 40C for 10 days, 70C for 2 hours and 150C for 30 minutes into the food simulants (water, 3% acetic acid, 10% ethanol and isooctane) and then they were filtered. The extractables (surrogates contaminants) were quantified using chromatographic methods, with specific attributes for each case. It was used the solid-phase microextraction (SPME) for extracting contaminants, that were submitted to gas chromatography-mass spectrometry (GC-MS). The GC-MS and the GC with electron capture detector (GCECD) were other method also used. Throughout extractable measurements, the results obtained were correlated with the efficiency in each stage of the recycling process, with contaminants extraction in different food simulants and with the influence of different temperatures and time in the contaminants extraction. The influence of contaminants and of the recycling methods on the degradative process were also evaluated through parallel plate rheometry, capillary rheometry, melt flow index (MFI), differential scanning calorimetry (DSC) and tensile strength. By extractable measurements, the results obtained showed that the best method for efficient decontamination of post-consumed PP is when the co-rotating double screw with degassing is used. However, the same samples were sensitive to degradation process. It was observed that residual contaminants into the PP structure acted like degrading agents. So all the samples of PP which were recycled suffered change in their structure due to degradation. The results showed the presence of the residual contaminants led to an even more degradative effect in the polymer.

ASSUNTO(S)

reciclagem polipropileno reciclado embalagem para alimento descontaminação processamento por extrusão degradação recycling recycled polypropylene food packaging decontamination extrusion processing degradation engenharia de materiais e metalurgica

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