Sandra A. Cruz

Avaliação das propriedades reológicas de blendas de PEAD virgem/PEAD reciclado

Neste trabalho, as propriedades reologicas de blendas de PEAD virgem e PEAD reciclado, em diferentes porcentagens, foram avaliadas em regime permanente, transiente e dinâmico de cisalhamento utilizando-se reometria cone-placa e reometria capilar. Embalagens de PEAD pos-consumo foram coletadas e submetidas aos processos basicos de recuperacao de plasticos: lavagem, moagem e secagem. Formulacoes, previamente estabilizadas, contendo 0, 25, 50, 75 e 100% de material reciclado, adicionado a resina virgem, foram reprocessadas por extrusao e posterior injecao. Das medidas das propriedades reologicas foi possivel concluir que a incorporacao de material reciclado proveniente de residuo pos-consumo a resina virgem promove, neste caso, uma diminuicao da massa molar e aumento na sua distribuicao. Alem disso, um estudo das propriedades reologicas permite a predicao de seu comportamento frente ao processamento de resinas recicladas pos-consumo.

Comparison between solid phase microextraction (SPME) and hollow fiber liquid phase microextraction (HFLPME) for determination of extractables from post-consumer recycled PET into food simulants.

Hollow fiber liquid phase microextraction (HFLPME) and solid phase microextraction (SPME) methods for pre-concentration of contaminants (toluene, benzophenone, tetracosane and chloroform) in food simulants were investigated. For HFLPME 1-heptanol, 2-octanone and dibutyl-ether were studied as extracting solvents. Analysis by gas chromatography coupled to mass spectrometry (GC-MS), flame ionization (GC-FID) and electron capture detectors (GC-ECD) were carried out. In addition, the methods were employed to evaluate the safety in use of a PET material after the recycling process (comprising washing, extrusion and solid state polymerization (SSP)) through extractability studies of the contaminants using 10% (v/v) ethanol in deionized water and 3% (w/v) acetic acid in deionized water as food simulants in different conditions: 10 days at 40°C and 2h at 70°C. The HFLPME preconcentration method provided increased sensitivity when compared to the SPME method and allowed to analyze concentration levels below 10 µg surrogate per kg food simulant. The results of the extractability studies showed considerable reductions after the extrusion and SSP processes and indicated the compliance with regulations for using recycled PET in contact with food.

Polímeros reciclados para contato com alimentos

Os residuos solidos urbanos (RSUs) sao atualmente um dos maiores problemas ambientais, por serem gerados em grande quantidade e ocuparem extensos espacos por um longo periodo, resultando na diminuicao do tempo de vida util dos aterros sanitarios. Os polimeros constituem um grande percentual da composicao do RSUs, sendo que as embalagens plasticas contribuem com maior volume e massa. Apesar da reciclagem de polimeros estarem se consolidando no Brasil, gracas ao seu mercado ascendente e promissor, existem ainda restricoes quanto a sua utilizacao em contato com alimentos devido aos eventuais processos de migracao de contaminantes que podem ocorrer da resina reciclada para o alimento. Por outro lado, dados recentes do setor indicam que a maior parte do consumo de resina virgem e destinada, justamente, para o mercado de embalagens alimenticias. Assim, o desenvolvimento e o gerenciamento de tecnologias que possibilitem o retorno destes materiais a sua aplicacao original e de grande importância para sociedade contemporânea. Em um panorama geral, este trabalho aborda as exigencias e limitacoes do uso de polimeros reciclados para contato com alimentos.

The Effects of Accelerated Aging and Contact with Food Simulants on the Adhesion of Amorphous Hydrogenated Carbon Films Deposited on Clarified Polypropylene

This work focuses mainly on the influence of time, temperature, and contact with food simulants on the adhesion of amorphous hydrogenated carbon (a-C:H) films obtained by plasma-enhanced chemical vapor deposition (PECVD) in clarified polypropylene (cPP). Two types of films prepared by PECVD were studied: diamond-like carbon (DLC) and polymer-like carbon (PLC) films that can both act as a functional barrier. The adhesion between the film and polymer substrates is critical in relation to the barrier effectiveness during the packaging shelf life. Therefore, the adhesion was analyzed by a tape test and scanning electron microscopy (SEM). The films were exposed to Food and Drug Administration (FDA) listed food simulants and were submitted to an accelerated aging test to evaluate the long-term adhesion performance of a-C:H films. The chemical alterations on the surface related to the accelerated aging test and the liquid simulants were analyzed by a contact angle test. It showed that the polarity of a-C:H films increased after immersion in liquid simulants, indicating a change on the surface. Before the accelerated aging test, the SEM micrographs and the tape test indicated that the PLC film has a structure with lower surface tension and, therefore, regions with fewer detachment points in relation to the DLC film. The results obtained in this study showed that the adhesion behavior and preservation of the a-C:H structure (DLC or PLC) are related to intrinsic factors such as the type of film structure (flexible or rigid) and the polymeric substrate.

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

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.

Degradation process of low molar mass poly(ethylene terephthalate)/organically modified montmorillonite nanocomposites Effect on structure, rheological, and thermal behavior

The aim of this work is to investigate the degradation of low molar mass poly(ethylene terephthalate) (PET)/organically modified montmorillonite (OMMT) clay nanocomposites prepared by melt processing. The rheological behavior in combination with transmission electron microscopic images suggests an intercalation and therefore a percolating network. Furthermore, the results indicate that the increase of organoclay content caused a degradation of PET during processing of PET/OMMT nanocomposites, once it was observed the PET molar mass decreases. The effect mentioned could be attributed to an increase of Brønsted acidic sites on the platelet surface, which is produced by the Hofmann elimination reaction of ammonium, and also the presence of residual metal compounds on clay surface might possibly favored the polymer matrix degradation process.

Barrier properties to surrogates of hydrogenated carbon nano-films deposited on PET by plasma-enhanced chemical vapour deposition

Poly(ethylene terephthalate) resin was contaminated with a series of surrogates using a US Food and Drug Administration protocol. The contaminated samples were coated with two different kinds of hydrogenated amorphous carbon thin films (a-C:H): one with diamond-like hydrogenated amorphous carbon and another with polymer-like hydrogenated carbon (PLCH) phases. To evaluate the barrier properties of the a-C:H films, migration assays were performed using food simulants. After the tests, analysis by gas chromatography with different detectors was carried out. The appearance of the films before and after the migration experiments was studied by field emission scanning electron microscopy. The results showed that a-C:H films have good barrier properties for most of the evaluated compounds, mainly when they are deposited as PLCH phase.