RESUMO A utilização de polímeros termoplásticos reciclados a partir de embalagens para a preparação de compósitos com fibras vegetais é uma alternativa tecnológica de grande potencial que pode conciliar viabilidade econômica com benefícios ambientais. No Brasil, muitos estudos têm sido feitos para a utilização de fibras vegetais em compósitos com matriz polimérica devido à grande disponibilidade de resíduos desses materiais. O País também merece destaque pelo alto índice de reciclagem mecânica de polímeros termoplásticos, principalmente do polímero poli(tereftalato de etileno) (PET). O presente trabalho teve como objetivo a preparação de compósitos por processamento termomecânico a partir de fibra de cana-de-açúcar tratada por explosão a vapor com matriz polimérica de PET e a avaliação do comportamento das propriedades do material em comparação aos compósitos com fibras não tratadas. Apesar das mudanças significativas na morfologia das fibras de cana-de-açúcar com o tratamento por explosão a vapor, não houve diferenças significativas nas propriedades dos compósitos PET/fibra tratada com relação aos compósitos PET/fibra in natura devido à não penetração da matriz polimérica no interior da estrutura da fibra modificada com o tratamento. O uso de outros tipos de matrizes poliméricas recicladas e adaptações nas operações de processamento dos materiais são alternativas que podem ainda potencializar o uso de fibra de cana-de-açúcar tratada por explosão a vapor na preparação de compósitos poliméricos e contribuir para a produção de materiais ambientalmente sustentáveis.

ABSTRACT The use of recycled thermoplastic polymers from packaging and natural fibers for preparation of polymeric composites is a technological alternative of high potential to conciliate economic viability with environmental benefits. In Brazil, several studies have been performed aiming the use of natural fibers in polymeric composites due to the high availability of the agricultural waste. The high index of mechanical recycling of thermoplastic polymers, mainly of the polymer polyethylene terephthalate (PET), also worth mentioning in the Country. This study aimed the preparation of PET/sugarcane fiber composites by thermomechanical processing after treating of the fibers by steam explosion and the evaluation of the composites properties when compared with composites using fibers without treatment. Although of the significant changes in the fiber morphology with steam explosion treatment, there were not significant difference between properties of the composites with treated fibers and the composites with not treated fibers due to the insufficient penetration of the polymeric matrix into structure of the modified fiber after treatment. The use of others recycled polymeric matrix as well as adjustments in the operations for materials processing are alternatives that can improve the use of sugarcane fiber treated by steam explosion in the preparation of polymeric composites, contributing for production of environmentally sustainable materials.

Carbon fiber composites are used in several industries such as, aerospace, automotive, civil engineering, sports goods and technical applications due to its low-weight, strength and stiffness. However, the technology of recycling of these thermosetting polymer composites remains an engineering challenge because of their cross-linked structures that impede their reprocessing by simple heating. The aim of this work was to study the influence of the amount and dimensions of carbon fibers arising from composite waste into a new composite of polypropylene matrix. In order to carry out the study, the carbon fiber composite waste has been mechanically processed for the production of chopped fibers with two different lengths (4.5 mm and 3.0 mm). Thermoplastic composites made of chopped carbon fiber/ polypropylene at proportions 1%, 5% and 7% in fiber weight content were obtained by extrusion and injection process. Then, a series of laboratory test (mechanical, thermal and morphological) were performed in order to characterize the composite material obtained. The results showed that the fibers were capable of causing a reinforcing, even though the new composite presents a complex phase system with low adhesion between the recycled carbon fibers and the polypropylene matrix.

Poly(ethylene tereftalate) (PET) is a polymer highly susceptible to the hydrolytic reactions that occur during applications and mainly in thermomechanical processing. These reactions lead to the decrease of molecular weight of the polymer, limiting the recycling number of the material. The reactive extrusion of the PET in presence of chain extenders is an alternative to recover mechanical and rheological properties that were depreciated by the polymer degradation. In this study, PET wastes from nonwoven fabrics production were extruded in presence of the secondary stabilizer Irgafos 126 (IRG) on variable concentrations. The results showed that Irgafos 126 increased molecular weight, decreased crystallinity and changed processing behavior of the PET, similarly to the effects produced by the well-known chain extender pyromellitic dianhydride (PMDA), showing that the secondary stabilizer Irgafos 126 can also act as a chain extender for the PET.

O consumo crescente de materiais poliméricos em diversas formas de aplicação leva à produção de uma quantidade enorme de resíduos pós-consumo e pós-industriais com potencial poluidor elevado. A reciclagem mecânica é uma das maneiras mais adequadas para contornar os problemas gerados por estes rejeitos, uma vez que permite conciliar interesse econômico com benefícios ambientais. Neste trabalho foi feito um estudo sobre a reciclagem de rejeitos pós-industriais de poli(tereftalato de etileno) (PET) provenientes da fabricação de mantas de tecido não tecido e de resíduos de poliamida (PA) oriundos de pneus usados na forma de blendas, produzidas por meio de extrusão reativa dos dois resíduos em presença de catalisador. Os resultados obtidos a partir de caracterização térmica e química das blendas evidenciaram a ocorrência de trans-reações entre segmentos de cadeia polimérica dos dois polímeros, possibilitando a compatibilização do sistema. A produção de blendas PET/PA se configura como uma forma adequada para a reciclagem dos rejeitos de PET e de PA.

The increasing use of polymeric materials in several applications leads to the production of a high amount of post consume and post industrial wastes with expressive pollutant potential. Mechanical recycling is an important way to decrease the problems caused by these wastes because it allows one to associate economic viability with environmental benefits. In this paper a study was carried out on the recycling of poly(ethylene tereftalate) (PET) wastes from the production of nonwoven fabrics (NWF) and of polyamide (PA) wastes from old tires for production of polymeric blends via reactive extrusion in the presence of trans-reaction catalysts. The results from thermal and chemical characterization indicated trans-reactions between segments of polymeric chains of the two polymers, promoting the system compatibilization. The production of PET/PA blends is an interesting alternative for recycling PET and PA wastes.

Compostos orgânicos e inorgânicos, tais como óxidos, sais de metais, compostos policíclicos e azo, são freqüentemente usados como colorantes para polímeros. O pigmento vanadato de bismuto vem sendo usado como uma alternativa a pigmentos baseados em cádmio. Corantes baseados na antraquinona pertencem a classe de colorantes policíclicos amplamente usados em polímeros. Além de suas características como colorantes, o vanadato de bismuto e colorantes a base de antraquinona apresentam atividade fotocatalítica ou propriedades fotoquímicas que podem influenciar o mecanismo e a cinética de fotodegradação do polímero que o contem. Neste trabalho estudou-se a influencia do pigmento vanadato de bismuto e de um corante a base de antraquinona sobre a fotodegradação do policarbonato. Para tanto, amostras de policarbonato contendo os colorantes foram submetidas a envelhecimento fotoquímico de acordo com as recomendações da ASTM G53. Os resultados indicaram que o vanadato de bismuto acelera a fotodegradação do policarbonato, causando uma acentuada perda nas propriedades mecânicas e aumento na concentração de hidroperóxido durante o envelhecimento. As características relacionadas a cor do pigmento também foram alteradas. O comportamento do policarbonato contendo o vanadato de bismuto frente a fotodegradação é atribuído a possíveis reações envolvendo o polímero e o pigmento promovidas pela radiação UV. Por outro lado, a presença de um corante a base de antraquinona aparentemente estabilizou o policarbonato frente à fotodegradação através de um mecanismo de desativação de estados excitados no policarbonato.

Both inorganic and organic compounds, such as oxides or salts of metals and polycyclic and azo compounds, are frequently used as colorants in polymeric systems. Bismuth vanadate pigment has been used as an environmentally friendly alternative for cadmium containing pigments and anthraquinone dyes represent a polycyclic colorant class of wide use in polymers. Besides their coloring properties, both bismuth vanadate and anthraquinone present photocatalytic activity or photochemical properties that can influence the mechanism and the kinetics of the photodegradation of the polymer into which they are incorporated. In this paper the influence of bismuth vanadate pigment and anthraquinone dye on the photodegradation of polycarbonate was evaluated. For this purpose, samples of polycarbonate containing the colorants were submitted to photochemical aging following the recommendations of ASTM G53. Bismuth vanadate accelerates the photodegradation of polycarbonate, causing a faster drop in the mechanical properties and an increase in the hydroperoxide concentration during the aging process. The coloring ability of the pigment is also affected. The photodegradation behavior of polycarbonate in presence of bismuth vanadate may be caused by a possible direct chemical reaction between pigment and polymer, promoted by UV radiation. On the other hand, the presence of anthraquinone dye seems to stabilize the polycarbonate against photodegradation through a deactivation mechanism of the excited state.

Dyes and pigments are additives used in polymers to improve mainly the aesthetic properties of the material. However, the incorporation of these additives can directly affect polymer stability. The colorants can drastically decrease the lifetime and the performance of the material or can act as a stabilizer, improving significantly the stability of the polymer against degradation. Interaction between colorants and polymers is the cause of the stability changes. Some mechanisms are proposed to explain the action of colorants on polymers. However it is difficult to foresee this action without experiments. This work reviews the main mechanisms involved in the degradation and stabilization of polymers containing colorants.