Influência do envelhecimento termo-oxidativo nas propriedades mecânicas e de amarelamento de blendas de poliestireno com borracha reciclada de estireno-butadieno (SBR)

Este trabalho teve como objetivo avaliar o envelhecimento termo-oxidativo, nas propriedades mecânicas e deíndice de amarelamento (YI), de blendas de poliestireno com borracha reciclada (SBRr), compatibilizadas.As blendas foram preparadas, inicialmente, em uma extrusora de rosca dupla corrotacional e, posteriormente,os grânulos extrudados foram moldados por injeção. Para efeito comparativo, o poliestireno de alto impactocomercial (HIPS) foi processado nas mesmas condições das blendas. Os resultados da caracterização doSBRr indicaram, em sua composição, cargas de sílica, carbonato de cálcio, talco e óxido de zinco, enquantoque, por termogravimetria, verificou-se duas etapas de decomposição térmica. Verificou-se que a resistênciaao impacto diminuiu, significativamente, nos 15 dias iniciais do envelhecimento, e, subsequentemente, apresentouuma tendência de estabilização com pequenas oscilações. As propriedades de módulo de elasticidade,resistência e alongamento na ruptura sob tração apresentaram o mesmo comportamento da resistência ao impacto,redução acentuada nos 15 dias inicias, seguida de estabilização, com o decorrer do envelhecimento.Quando a blenda foi compatibilizada com 5% de estireno-butadieno-estireno (SBS), foram observadas asmelhores propriedades, antes e após o envelhecimento, apresentando resistência ao impacto equiparáveis aoHIPS. A perda de massa das blendas indicou extração de componentes voláteis. Por índice de amarelamento(YI), observou-se, nas blendas, um aumento brusco nos 15 dias iniciais e, em seguida, estabilidade, com umataxa de amarelamento praticamente constante. Até 30 dias de envelhecimento, o HIPS apresentou uma baixataxa de amarelamento, e, posteriormente, ocorreu uma intensificação no YI. No geral, as blendas obtidas pormistura mecânica apresentaram comportamento similar ao HIPS. Porém, somente quando a blenda foi compatibilizadacom SBS que o comportamento de impacto apresentou o mesmo patamar do HIPS.Palavras-chave: envelhecimento, termo-oxidação, blendas poliméricas, propriedades mecânicas, índice deamarelamento

Efeito das variáveis reacionais na síntese de um polímero biodegradável funcionalizado: PCL-g-MA

A Poli(ɛ-caprolactona) (PCL) é um termoplástico sintético biodegradável que tem sido foco de estudos emnovos “polímeros verdes”, devido principalmente as suas boas propriedades mecânicas, o que a torna competitivacom outros polímeros convencionais e biopolímeros, tais como: Poli(ácido lático) (PLA), Poli(hidroxibutirato) (PHB). O objetivo deste trabalho foi a enxertia de grupos reativos anidrido maleico (MA)na PCL para a produção de um polímero funcional biodegradável. A síntese de enxertia do anidrido maleicona PCL ocorreu em um misturador interno de laboratório, utilizando concentrações de 2,5 e 5 % de MA e de0,3 e 0,5% do iniciador peróxido de dicumila (DCP) em duas temperaturas de processo, 110oC e 160oC. Ametodologia do planejamento fatorial 23 foi usada visando à otimização dos experimentos, assim como tambémpara avaliar a eficiência das condições reacionais empregadas para a funcionalização da PCL. Os resultadosindicaram que o anidrido maléico foi enxertado na PCL usando o iniciador peróxido de dicumila. Aporcentagem de anidrido maléico grafitizado (%gMA) foi obtida por titulação e comprovada por Espectroscopiana região do Infravermelho por Transformada de Fourier (FTIR). Através dos resultados obtidos podeseinferir que um maior teor (5,0%) de MA favoreceu positivamente a enxertia. No entanto, acima de determinadaquantidade, possivelmente ocorre uma saturação do sistema e a tendência é a recombinação.Palavras-chave: Funcionalização, anidrido maléico, Poli (ɛ-caprolactona), polímeros biodegradáveis

Propriedades reológicas de blendas de polipropileno copolímero/polipropileno reciclado oriundo de recipientes industriais

Neste estudo, foram avaliadas blendas de polipropileno copolímero (PPCop)/polipropileno reciclado (PPRec), proveniente de baldes industriais pós-consumo, em três proporções diferentes (80:20; 60:40 e 40:60% em peso). As blendas foram avaliadas por índice de fluidez, reometria de torque e reologia em regime dinâmico-oscilatório. Os resultados de índice de fluidez indicaram que a mistura de material reciclado com o PPCop promove uma diminuição da massa molar, em comparação ao PPCop. Por reometria de torque, verificou-se que as blendas melhoraram a processabilidade em comparação ao PPCop. Além disso, as blendas apresentaram estabilidade ao longo do processamento, indicando ausência de degradação para as condições de processos utilizadas. Por meio dos ensaios em regime dinâmico-oscilatório, observou-se que, em baixas frequências ( 1 rad/s), o PPCop e as blendas (PPCop/PPRec) apresentam um comportamento de fluido Newtoniano, enquanto que, para frequências maiores que 1 rad/s, um comportamento de fluido pseudoplástico. Os valores dos pontos de intersecção (G’ = G”) das curvas de módulo de armazenamento (G’) e de módulo de perda (G’’), em função da frequência angular (ω), indicaram que as blendas apresentaram uma redução da massa molar, sendo mais pronunciada na composição contendo 60% de PPRec. Os resultados reológicos das blendas PPCop/PPRec foram de grande relevância, uma vez que permitem analisar o comportamento de blendas contendo material reciclado.Palavras-chave: polipropileno, polipropileno reciclado, blendas poliméricas, reologia.

Educomunicação e suas áreas de intervenção: Novos paradigmas para o diálogo intercultural

oai:omp.abpeducom.org.br:publicationFormat/1O material aqui divulgado representa, em essência, a contribuição do VII Encontro Brasileiro de Educomunicação ao V Global MIL Week, da UNESCO, ocorrido na ECA/USP, entre 3 e 5 de novembro de 2016. Estamos diante de um conjunto de 104 papers executivos, com uma média de entre 7 e 10 páginas, cada um. Com este rico e abundante material, chegamos ao sétimo e-book publicado pela ABPEducom, em seus seis primeiros anos de existência. A especificidade desta obra é a de trazer as “Áreas de Intervenção” do campo da Educomunicação, colocando-as a serviço de uma meta essencial ao agir educomunicativo: o diálogo intercultural, trabalhado na linha do tema geral do evento internacional: Media and Information Literacy: New Paradigms for Intercultural Dialogue

Toughening of polystyrene using styrene-butadiene rubber (SBRr) waste from the shoe industry

Abstract The vulcanized rubber waste from the shoe industry causes environmental damage when it is incinerated or inappropriately discarded, turning this into a problem of major concern. Therefore, this study had as the main objective the Polystyrene (PS) toughening using different contents of white vulcanized styrene-butadiene rubber (SBRr) waste produced in the shoe industry. The mixtures were initially prepared in a co-rotational double screw extruder and, thereafter, the extruded granules were injection molded. Analyzed were the rheological, mechanical, thermomechanical properties and morphology of the produced blends. The rheological results showed a viscosity increase as the SBRr concentration was augmented, leading to a higher stability when compared to pure Polystyrene. Verified was an increase of impact resistance of 189% to the blend that contained 50% of SBR rather than pure Polystyrene. On the other hand, the traction properties, hardness Shore D, thermal deflection temperature (HDT) and Vicat softening temperature of the blends tended to decrease when compared to pure Polystyrene results. However, as this SBR waste is made up of a complex mixture of SBR, filler, processing additions, curing agents and stabilizers, it probably acted in the sense of not causing such a drastic reduction of the properties, even using a high concentration of SBRr waste. The morphologies obtained with the SEM method (Scanning Electronic Microscope) were quite different and typical of immiscible blends. The results show that it is possible to obtain a new material with good properties, valuing a discarded industrial waste and avoiding environment aggression

Toughening of polystyrene using styrene-butadiene rubber (SBRr) waste from the shoe industry

<div><p>Abstract The vulcanized rubber waste from the shoe industry causes environmental damage when it is incinerated or inappropriately discarded, turning this into a problem of major concern. Therefore, this study had as the main objective the Polystyrene (PS) toughening using different contents of white vulcanized styrene-butadiene rubber (SBRr) waste produced in the shoe industry. The mixtures were initially prepared in a co-rotational double screw extruder and, thereafter, the extruded granules were injection molded. Analyzed were the rheological, mechanical, thermomechanical properties and morphology of the produced blends. The rheological results showed a viscosity increase as the SBRr concentration was augmented, leading to a higher stability when compared to pure Polystyrene. Verified was an increase of impact resistance of 189% to the blend that contained 50% of SBR rather than pure Polystyrene. On the other hand, the traction properties, hardness Shore D, thermal deflection temperature (HDT) and Vicat softening temperature of the blends tended to decrease when compared to pure Polystyrene results. However, as this SBR waste is made up of a complex mixture of SBR, filler, processing additions, curing agents and stabilizers, it probably acted in the sense of not causing such a drastic reduction of the properties, even using a high concentration of SBRr waste. The morphologies obtained with the SEM method (Scanning Electronic Microscope) were quite different and typical of immiscible blends. The results show that it is possible to obtain a new material with good properties, valuing a discarded industrial waste and avoiding environment aggression.</p></div

Toughening of polystyrene using styrene-butadiene rubber (SBRr) waste from the shoe industry

<div><p>Abstract The vulcanized rubber waste from the shoe industry causes environmental damage when it is incinerated or inappropriately discarded, turning this into a problem of major concern. Therefore, this study had as the main objective the Polystyrene (PS) toughening using different contents of white vulcanized styrene-butadiene rubber (SBRr) waste produced in the shoe industry. The mixtures were initially prepared in a co-rotational double screw extruder and, thereafter, the extruded granules were injection molded. Analyzed were the rheological, mechanical, thermomechanical properties and morphology of the produced blends. The rheological results showed a viscosity increase as the SBRr concentration was augmented, leading to a higher stability when compared to pure Polystyrene. Verified was an increase of impact resistance of 189% to the blend that contained 50% of SBR rather than pure Polystyrene. On the other hand, the traction properties, hardness Shore D, thermal deflection temperature (HDT) and Vicat softening temperature of the blends tended to decrease when compared to pure Polystyrene results. However, as this SBR waste is made up of a complex mixture of SBR, filler, processing additions, curing agents and stabilizers, it probably acted in the sense of not causing such a drastic reduction of the properties, even using a high concentration of SBRr waste. The morphologies obtained with the SEM method (Scanning Electronic Microscope) were quite different and typical of immiscible blends. The results show that it is possible to obtain a new material with good properties, valuing a discarded industrial waste and avoiding environment aggression.</p></div

Tailoring Poly(lactic acid) (PLA) Properties: Effect of the Impact Modifiers EE-g-GMA and POE-g-GMA

Poly(ethylene-octene) grafted with glycidyl methacrylate (POE-g-GMA) and ethylene elastomeric grafted with glycidyl methacrylate (EE-g-GMA) were used as impact modifiers, aiming for tailoring poly(lactic acid) (PLA) properties. POE-g-GMA and EE-g-GMA was used in a proportion of 5; 7.5 and 10%, considering a good balance of properties for PLA. The PLA/POE-g-GMA and PLA/EE-g-GMA blends were processed in a twin-screw extruder and injection molded. The FTIR spectra indicated interactions between the PLA and the modifiers. The 10% addition of EE-g-GMA and POE-g-GMA promoted significant increases in impact strength, with gains of 108% and 140%, respectively. These acted as heterogeneous nucleating agents in the PLA matrix, generating a higher crystallinity degree for the blends. This impacted to keep the thermal deflection temperature (HDT) and Shore D hardness at the same level as PLA. By thermogravimetry (TG), the blends showed increased thermal stability, suggesting a stabilizing effect of the modifiers POE-g-GMA and EE-g-GMA on the PLA matrix. Scanning electron microscopy (SEM) showed dispersed POE-g-GMA and EE-g-GMA particles, as well as the presence of ligand reinforcing the systems interaction. The PLA properties can be tailored and improved by adding small concentrations of POE-g-GMA and EE-g-GMA. In light of this, new environmentally friendly and semi-biodegradable materials can be manufactured for application in the packaging industry

Tailoring Nylon 6/Acrylonitrile-Butadiene-Styrene Nanocomposites for Application against Electromagnetic Interference: Evaluation of the Mechanical, Thermal and Electrical Behavior, and the Electromagnetic Shielding Efficiency

Nylon 6/acrylonitrile-butadiene-styrene nanocomposites were prepared by mixing in a molten state and injection molded for application in electromagnetic interference shielding and antistatic packaging. Multi-wall carbon nanotubes (MWCNT) and maleic anhydride-grafted ABS compatibilizer were incorporated to improve the electrical conductivity and mechanical performance. The nanocomposites were characterized by oscillatory rheology, Izod impact strength, tensile strength, thermogravimetry, current-voltage measurements, shielding against electromagnetic interference, and scanning electron microscopy. The rheological behavior evidenced a severe increase in complex viscosity and storage modulus, which suggests an electrical percolation phenomenon. Adding 1 to 5 phr MWCNT into the nanocomposites produced electrical conductivities between 1.22 &times; 10&minus;6 S/cm and 6.61 &times; 10&minus;5 S/cm. The results make them suitable for antistatic purposes. The nanocomposite with 5 phr MWCNT showed the highest electromagnetic shielding efficiency, with a peak of &ndash;10.5 dB at 9 GHz and a value around &ndash;8.2 dB between 11 and 12 GHz. This was possibly due to the higher electrical conductivity of the 5 phr MWCNT composition. In addition, the developed nanocomposites, regardless of MWCNT content, showed tenacious behavior at room temperature. The results reveal the possibility for tailoring the properties of insulating materials for application in electrical and electromagnetic shielding. Additionally, the good mechanical and thermal properties further widen the application range

The Effect of ZnO on the Failure of PET by Environmental Stress Cracking

The aim of the present work is to evaluate the effect of NaOH solution as a stress cracking agent on the thermal and tensile properties of PET and PET/ZnO composites. The solutions were applied during tensile testing and the effects were monitored by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and testing the actual mechanical properties. The rate of crystallization was increased when the samples were exposed to NaOH, as observed by both cold and melt crystallization; this is possibly due to the reduction in molar mass of the PET molecules caused by NaOH. During melting, the DSC peaks became more complex, which is probably due to the distinct macromolecular mass, as well as crystallites with different sizes and levels of perfection. According to TGA analyses, no drastic changes were observed on the thermal stability of PET due to the action of NaOH. The tensile properties were shown to decrease drastically upon exposure to NaOH, which is the main symptom of stress cracking, leading to increased fragility, as also observed in the scanning electron microscopy (SEM) images. The presence of ZnO improved PET crystallization and provided some protection against the harmful effects of NaOH