Scielo RSS <![CDATA[PolĂ­meros]]> vol. 25 num. 2 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Melt processing of polymer biocomposites]]> A coupled device extruder and injection moulding were used to prepare biocomposites in order to provide a continuous and large-scale production, and overcome the fiber degradation inside the extruder. Two types of biocomposites were prepared, Sisal/poly(buthylene adipate-co-terephthlate) – PBAT and Juta/poly(lactide acid)/poly(buthylene adipate-co-terephthlate) blend. The biocomposites were prepared with fiber as-received and alkaline treated. The mechanical properties of biocomposites were increased by the fibers content; and the alkaline treatment was efficient to promote a good adhesion between fiber and polymer. In the case of the Juta fiber, the alkaline treatment used was too strong and led to fiber degradation. The results presented here show an alternative and continuous process to obtain biocomposites with relevant mechanical properties using fiber roving and avoiding fiber degradation. <![CDATA[New copolymer of acrylamide with allyl methacrylate and its capacity for the removal of azo dyes]]> The copolymerization reactions of Acrylamide (AA) with the different mole ratios of allyl methacrylate (AMA) such as 25/75, 50/50 and 75/25 were studied by radical polymerization under argon atmosphere using 2,2’-Azobis (isobutyronitri1e) (AIBN) as initiator. The copolymers were characterized with Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TG). FTIR spectra showed that the C=O, C-N and N-H groups in copolymers remained during the copolymerization. It is concluded from the thermograms that Poly(AA-co-AMA) copolymers which contained different ratios of monomer and comonomer exhibit similar thermal behavior. Adsorption capacity, kinetic and isotherm studies of Direct Brown 2 onto the copolymers have been evaluated. Different factors such as the monomer ratio, pH, initial dye concentration, copolymer dosage and contact time affecting the removal process were studied. It was found that the adsorption process agreed with the Freundlich and Dubinin-Raduskevich model and the adsorption of Direct Brown 2 depended on the acrylamide content and pH of the solution. The standard Gibb’s free energy was determined as - 14.7 kJ/mol, which means that adsorption occurred spontaneously and the process is feasible. Increasing the acrylamide content led to increased adsorption of Direct Brown 2 on the copolymer. Moreover, adsorption kinetic studies showed that the adsorption followed a pseudo-second-order kinetic model, indicating that the chemical adsorption was the rate-limiting step. These results show that Poly(AA-co-AMA) can be used as adsorbent for water pollutants such as Direct Brown 2 and has potential applications in related industrial and environmental areas. <![CDATA[Synthesis of polycationic bentonite-ionene complexes and their benzene adsorption capacity]]> The purpose of this work was to structurally modify clays in order to incorporate water-insoluble molecules, such as petroleum hydrocarbons. The potential for ion exchange of quaternary ammonium salts was studied, which revealed their ability to interact with anions on the cationic surface, for environmental applications of the material. Ionenes, also known as polycations, have many potential uses in environmental applications. In this work, cationic aliphatic ammonium polyionenes, specifically 3,6-ionene and 3,6-dodecylionene, were prepared for incorporation into clay to form bentonite-ionene complexes. The intercalation of bentonite with ionene polymers resulted in an increase in the basal spacing of 3,6-dodecylionene from 1.5-3.5 nm. The higher d001 spacing of 3,6-dodecylionene samples than that of 3,6-ionene samples may be attributed to their longer tail length. The behavior of the TG/DTG curves and the activation energy values suggest that 3,6-dodecylionene (E = 174.85 kJ mol–1) is thermally more stable than 3,6 ionene (E = 115.52 kJ mol–1) complexes. The adsorption of benzene by 3,6-ionene and 3,6-dodecylionene was also investigated. The increase in benzene concentrations resulted in increased benzene adsorption by the sorbents tested in this work. The sorption capacity of benzene on ionene-modified bentonite was in the order of 3,6-dodecylionene &gt; 3,6-ionene. <![CDATA[Biodegradation evaluation of bacterial cellulose, vegetable cellulose and poly (3-hydroxybutyrate) in soil]]> In recent years, the inappropriate disposal of polymeric materials has increased due to industrial development and increase of population consumption. This problem may be minimized by using biodegradable polymers, such as bacterial cellulose and poly(hydroxybutyrate), from renewable resources. This work was aimed at monitoring and evaluating degradation of bacterial cellulose, vegetable cellulose and poly(3-hydroxybutyrate) using Thermogravimetric Analysis and Scanning Electron Microscopy. Controlled mass polymer samples were buried in pots containing soil. Samples were removed in 30 day intervals up to 180 days. The results show that the mass of the polymer increased in the first month when in contact with the soil but then it was degraded as evidenced by mass loss and changes on the sample surface. <![CDATA[Extraction of poly(3-hydroxybutyrate) from <em>Spirulina</em> LEB 18 for developing nanofibers]]> The objective of this study was to extract poly(3-hydroxybutyrate) (PHB) from the microalgal biomass of Spirulina LEB 18 for the development of nanofibers by electrospinning method. Different extraction methods were tested. The maximum yield obtained was 30.1 ± 2%. It was possible to produce nanofibers with diameters between 826 ± 188 nm and 1,675 ± 194 nm. An increase in the nanofiber diameter occurred when a flow rate of 4.8 μL min-1 and a capillary diameter of 0.90 mm were used. The nanofibers produced had up to 34.4% of biomass additives, i.e., non-PHB materials. This can be advantageous, because it enables the conservation of microalgal biomass compounds with bioactive functions. <![CDATA[Synthesis of graft copolymers of acrylamide for locust bean gum using microwave energy: swelling behavior, flocculation characteristics and acute toxicity study]]> The graft copolymer of locust bean gum (LBG) and acrylamide has been synthesized by microwave assisted method using potassium persulphate (KPS) as an initiator in aqueous medium. Different reaction parameters such as time, initiator concentration, monomer concentration, polymer concentration, and microwave power were studied to get maximum graft copolymer. The grafted copolymer was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The graft copolymer exhibited pH switching on-off behavior depending on the pH of the external medium. Flocculation capacity of LBG and LBG-graft-polyacrylamide for both coking and non-coking coals has been studied. Results indicated that the graft copolymer exhibited good flocculation properties compared to native polymer. The graft copolymer was non-toxic in the acute toxicity study, since the acute single dose did not cause any toxic signs, or symptoms. All mice treated with the graft copolymer survived beyond the 14 days of observation period. <![CDATA[Flexible thermoplastic composite of Polyvinyl Butyral (PVB) and waste of rigid Polyurethane foam]]> This study reports the preparation and characterization of composites with recycled poly(vinyl butyral) (PVB) and residue of rigid polyurethane foam (PUr), with PUr contents of 20, 35 and 50 wt %, using an extruder equipped with a Maillefer single screw and injection molding. The components of the composites were thermally characterized using differential scanning calorimetry (DSC) and thermogravimetry. The composites were evaluated by melt flow index (MFI), tensile and hardness mechanical tests and scanning electron microscopy (SEM). Tg determined by DSC of PVB sample (53 °C) indicated the presence of plasticizer (Tg of pure PVB is 70 °C). MFI of the composites indicated a viscosity increase with the PUr content and, as the shear rate was held constant during injection molding, higher viscosities promoted higher shear stresses in the composites, thereby causing breaking or tearing of the PUr particles. The SEM micrographs showed low adhesion between PVB and PUr and the presence of voids, both inherent in the rigid foam and in the interphase PVB-PUr. The SEM micrographs also showed that PVB/PUr (50/50) composite exhibited the smallest particle size and a more homogeneous and compact structure with fewer voids in the interface. The stiffness of the composites increases with addition of the PUr particles, as evidenced in the mechanical tests. <![CDATA[Determination of ENB content in EPDM elastomer by using relative bands of transmission FT-IR]]> Foi desenvolvida uma metodologia para a determinação do teor de 5-etilideno 2-norboneno (ENB) em amostras de borracha (elastômero puro), à base do copolímero de etileno-propileno-dieno (EPDM), por espectroscopia no infravermelho com transformada de Fourier (FT-IR) de transmissão, sendo as amostras analisadas, após pirólise controlada e em bico de Bunsen. Embora ambas as técnicas tenham apresentado boa precisão, a realizada por pirólise em bico de Bunsen, com uso de banda e concentração relativa, mostrou-se mais adequada à determinação e ao uso em cálculos complementares de teores de ET e P.<hr/>A methodology was developed for determining the 5-ethylidene-2-norbornene (ENB) content in unvulcanized (pure elastomer) ethylene-propylene-diene (EPDM) elastomer, by transmission Fourier Transform infrared spectroscopy (FT-IR), after pyrolysis with and without temperature (T) control. Although both techniques have shown good accuracy, the pyrolysis without T control technique, with relative bands and concentrations, was more suitable for the ENB content determination and for the complementary calculations of ET and P. <![CDATA[Evaluation of the characteristics of an epoxy resin with different degassing agents]]> Este trabalho tem por objetivo a busca por técnicas alternativas para diminuir a incidência de vazios em resinas poliméricas e, por consequência, em materiais compósitos. Foram produzidas formulações diferentes utilizando resina epóxi à base de éter diglicidílico do Bisfenol A, endurecedor de poliamina alifática com e sem a adição de diferentes aditivos desaerantes a base de éteres e ésteres modificados. As formulações produzidas foram submetidas a condições extremas de agitação e processamento, sendo posteriormente avaliadas quanto a incidência de bolhas e vazios, densidade, propriedades mecânicas, morfológicas e térmicas. Os resultados foram bastante positivos quanto à diminuição da quantidade e do tamanho de poros pela utilização de técnicas de desgaseificação a vácuo e pelo uso de aditivos desaerantes.<hr/>This study aims alternative techniques to reduce the incidence of voids in polymeric resins and in composite materials. Different formulations were prepared using epoxy resin based on bisphenol A diglycidyl ether and an aliphatic polyamine hardener, with and without the addition of different degasing agents based on modified esters and ethers. The formulations produced were subjected to extreme agitation and processing conditions and we evaluated the incidence of bubbles and voids, density, mechanical, morphological and thermal properties. The results were very positive. We observed the decrease in number and size of pores by the use of vacuum degassing techniques and degasing agent additives. <![CDATA[Magnetic microspheres based on poly(divinylbenzene-<em>co</em>-methyl methacrylate) obtained by suspension polymerization]]> Microesferas poliméricas à base de metacrilato de metila (MMA), divinilbenzeno (DVB) e material magnético foram preparadas via polimerização por suspensão. Foi estudada a influência da polimerização em suspensão ou semisuspensão, concentração de material magnético e concentração de divinilbenzeno sobre as características das microesferas obtidas. As partículas poliméricas foram caracterizadas por espectroscopia vibracional na região do infravermelho por transformada de Fourier (FT-IR), microscopia eletrônica de varredura, analisador de área específica e porosimetria, espalhamento de luz e magnetometria de amostra vibrante. O material magnético também foi caracterizado por FT-IR, além de difratometria de raios X e espectroscopia Mössbauer. Foram obtidas, com sucesso, microesferas poliméricas magnéticas à base de MMA e DVB (P(MMA-co-DVB)-M), contendo partículas magnéticas tanto na superfície quanto no interior da microesfera. As partículas obtidas através de polimerização em semisuspensão apresentaram tamanhos menores e distribuição de tamanhos de partículas mais estreita que as partículas obtidas através de suspensões convencionais. Os compósitos apresentaram um comportamento superparamagnético. As microesferas magnéticas sintetizadas neste trabalho têm potencial para serem modificadas e aplicadas como resinas de troca iônica ou suportes catalíticos.<hr/>Magnetic polymeric microspheres based on methyl methacrylate (MMA), divinylbenzene (DVB) and magnetic materials were prepared via suspension polymerization. We studied the influence of the suspension or semi-suspension polymerization, magnetic materials and divinylbenzene concentration on the characteristics of the microspheres. Polymeric particles were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy, accelerated surface area and porosimetry analyzer (ASAP), dynamic light scattering (DLS) and vibrating sample magnetometer (VSM). The magnetic materials were also characterized by FT-IR, X-ray diffraction and Mössbauer spectroscopy. Magnetic polymeric microspheres based on MMA and DVB (P(MMA-co-DVB)-M), containing magnetic particles on the surface or inside the microspheres, were successfully obtained. The polymer particles obtained through semi-suspension polymerization had smaller sizes and narrower particle size distribution than particles obtained by conventional suspension. The composites showed a superparamagnetic behavior. The magnetic microspheres synthesized in this work have potential to be modified and applied as ion-exchange resins or catalyst supports. <![CDATA[Evaluation of the fluorescence of enamel and dentin composite resins from different commercial sources]]> O objetivo do presente estudo foi analisar e avaliar comparativamente pelo método visual, a fluorescência das resinas compostas de cor A2 tanto para esmalte como para dentina, de sete diferentes marcas comerciais. Foram confeccionados para este experimento 52 corpos de prova de resina composta da cor A2 do tipo anterior/posterior, de diversas marcas comerciais disponíveis no mercado. Os corpos de prova foram obtidos com o auxílio de uma matriz de acrílico rígida e transparente. A fotoativação foi realizada com o aparelho 3M Curing Light 2500, com intensidade de 600 mW cm–2 pelo período de 40 s. Na superfície dos espécimes foi realizado um polimento com discos Soft-Lex. Foi confeccionada uma caixa de madeira, pintada com tinta preta fosca, para evitar reflexos e a ação de outras fontes de luz. O experimento foi realizado em câmara escura. Nesse experimento três avaliadores calibrados e instruídos avaliaram o grau de fluorescência dos espécimes, quando sob o efeito da iluminação de raios ultravioleta, e os classificaram de acordo com sua intensidade. Para cada avaliador os corpos de prova foram novamente misturados e dispostos aleatoriamente dentro da caixa. Para a avaliação da fluorescência entre resinas de esmalte e dentina, foi aplicado o teste estatístico de Kruskal-Wallis (p&lt;0,05). Constatou-se que as melhores resinas em termos de fluorescência para esmalte são das marcas comerciais Esthet-X HD e TPH, Opallis e Z350 e para dentina são Opallis e Evolu-X.<hr/>This study analyzes and comparatively evaluate, by a visual method, the fluorescence of the color A2 composite resins for both enamel and dentin from seven different commercial sources. We made fifty-two specimens of anterior/posterior composite resins. The specimens were obtained with a rigid and transparent acrylic matrix. The polymerization was done irradiating with the 3M Curing Light 2500, intensity of 600 mW cm–² for 40 s. The specimens were polished with Sof-Lex discs. A wooden box painted with flat black paint was used to avoid light reflection and other light sources and the experiment was conducted in a darkroom. Three calibrated and trained evaluators rated the degree of fluorescence of the specimens under the effect of ultraviolet light, and classified them according to their intensity. For each evaluator, the specimens were mixed and randomly arranged inside the box. For the evaluation of fluorescence between resin enamel and dentin, the Kruskal-Wallis test (p &lt;0.05) was applied. The best resins in terms of fluorescence of enamel are Esthet X-HD, TPH, Z350 and Opallis and for dentin are Opallis and Evolu-X. <![CDATA[Chemical characterization and healing effect of chitosan with low molar mass and acetylation degree in skin lesions]]> Inúmeras pesquisas buscam fármacos com propriedades cicatrizantes, capazes de reparar lesões cutâneas. O objetivo deste estudo foi caracterizar quimicamente uma quitosana e avaliar seus efeitos cicatrizantes em lesões cutâneas de ratos. A quitosana foi caracterizada quanto à viscosidade, massa molar, grau de acetilação, análise elementar, termogravimetria e espectroscopia na região do infravermelho. As propriedades cicatrizantes da quitosana foram avaliadas, para isso ratos adultos foram submetidos à excisão tecidual e tratados por 21 dias, sendo avaliados parâmetros macroscópicos, semanalmente, e microscópicos, ao final do experimento. A quitosana apresentou viscosidade de 5 mPa s, baixo grau de acetilação (GA=5,9%) e massa molar (132,0 kDa). Por análise elementar observou-se que a composição da quitosana se aproxima da fórmula C6H11O4N, suas principais bandas características foram observadas no espectro de infravermelho e a curva termogravimétrica mostrou que esta apresenta somente duas etapas de decomposição. Não houve diferença significativa na histologia, no 21º dia da lesão, entre os grupos controle e tratado, porém, macroscopicamente, a quitosana promoveu redução de 81,4% da largura das lesões, porcentagem significativamente superior à observada no grupo controle (71,2%), auxiliando a cura de lesões cutâneas, o que reforça seu potencial de aplicação médica.<hr/>Several researches look for drugs with healing properties, capable to cure skin lesions. The objective of this study was to chemically characterize one chitosan and evaluate its healing effects in mice skin lesions. The chitosan was characterized in relation to the viscosity, molar mass, acetylation degree, elementary analysis, thermogravimetry and infrared spectroscopy. To evaluate the healing properties of chitosan mices were submitted to tissue excision and treated during 21 days. The macroscopic parameters were weekly evaluated and the microscopic parameters at the end of the experiment. Chitosan presented viscosity of 5 mPa s, low acetylation degree (GA= 5.9%) and molar mass of 132.0 kDa. By elemental analysis, we observed that the composition of chitosan is similar to the formula C6H11O4N, its main characteristic bands were observed in the infrared spectrum and the thermogravimetric curve showed two decomposition steps. There was no significant difference on the histology between the control and the treated group after the 21st day of lesion. Macroscopically, chitosan caused the reduction of 81.4% of the lesions width, which is significantly superior to the observed reduction in the control group (71.2%), thus helping the cure of skin lesions. These results reinforces its potential use for medical application. <![CDATA[Chemical surface treatment and metallization of ABS, PVC and PVC/ABS blends]]> Visando à substituição do ABS em peças cromadas, amostras de PVC e blendas de PVC/ABS, na razão mássica de 20/80, 40/60 e 60/40, foram submetidas ao pré-tratamento em solução sulfocrômica sob diferentes condições de concentração, tempo e temperatura e sendo em seguida cromadas. As modificações na superfície das peças após o condicionamento foram analisadas por microscopia eletrônica de varredura, microscopia de força atômica e rugosidade. A qualidade da deposição metálica foi avaliada por inspeção visual e teste de adesão. Os resultados mostraram que, aumentando a concentração de PVC nas peças necessitou-se de condições operacionais mais agressivas, tais como maiores temperaturas de banho, tempo de imersão e concentração de solução sulfocrômica para que ocorresse a adesão da camada metálica. De todas as condições testadas com a solução condicionante sulfocrômica no tratamento das peças de PVC e blendas PVC/ABS de 20/80 e 40/60, a concentração de 350 g/L de ácido crômico e 400 g/L de ácido sulfúrico, temperatura de 70°C e tempo de imersão de 15 minutos, ocasionou deposição do metal em toda a superfície das peças, as quais foram aprovadas nos testes de adesão e corrosão.<hr/>To replace ABS in plated objects, samples of PVC and blends of PVC/ABS, in mass ratio of 20/80, 40/60 and 60/40, were subjected to step-conditioning (etching) in sulfochromic solution, under different conditions of concentration, time and temperature, being plated in sequence. Modifications of the surface of the samples after conditioning were analyzed by scanning electron microscopy, atomic force microscopy and roughness. The quality of metal deposition was evaluated by visual inspection and adhesion tests. Results show that increasing the amount of PVC in the blend required more aggressive operational conditions to promote metallic adhesion; higher temperature, immersion time and sulfochromic solution concentration. From all tested conditions with the sulfochromic solution for the treatment of PVC, and 20/80 and 40/60 PVC/ABS blend samples, the concentration of 350 g L–1 of chromic acid and 400 g L–1 of sulfuric acid at 70 oC and immersion time of 15 minutes, resulted in the deposition of metal layers in all evaluated specimens. These were approved in adhesion and corrosion tests. <![CDATA[Influence of nanoclay modification on the mechanical, thermo-mechanical and morphological properties of polyamide 6/Acrylonitrile-EPDM-Styrene blend-based nanocomposites]]> O efeito da organofilização da argila no comportamento mecânico, morfológico e termo-mecânico de nanocompósitos baseados em blendas de poliamida 6 )/acrilonitrila-EPDM-estireno foi estudado. Três nanoargilas foram utilizadas para a preparação dos nanocompósitos: duas montmorilonitas comerciais modificadas organicamente (Cloisite®30B and Cloisite® 20A) e uma montmorilonita sódica não modificada (Cloisite®Na+). Difração de raios-X em alto ângulo, microscopia eletrônica de transmissão e testes de tração e resistência ao impacto foram utilizados para avaliar o efeito da organofilização da nanoargila na morfologia e propriedades mecânicas dos materiais. As propriedades termo-mecânicas foram avaliadas por análise dinâmico mecânica e temperatura de deflexão térmica. Os resultados mostraram que a modificação da nanocarga afeta simultaneamente o grau de reforço da matriz, dispersão das lamelas de argila na blenda e tamanho da fase dispersa AES. A adição das diferentes nanoargilas aumenta o módulo elástico de todos os nanocompósitos ternários em relação à blenda pura sem argila. Por outro lado, um aumento na tenacidade foi obtido apenas para os sistemas com Cloisite®Na+. Um aumento significativo no módulo de armazenamento e HDT foi observado pela incorporação da Cloisite®30B na blenda.<hr/>The effect of clay organophilization on mechanical, morphological and thermo-mechanical behavior of polyamide-6/acrylonitrile-EPDM (ethylene/propylene/diene elastomer)-styrene blends was studied. Three nanoclays were used for the preparation of nanocomposites: two commercial organically modified montmorillonites (Cloisite®30B and Cloisite® 20A) and an unmodified sodium montmorillonite (Cloisite®Na+). We used wide angle X-ray scattering, transmission electron microscopy and mechanical tests to evaluate the effect of clay modification on the morphology and mechanical properties of the nanocomposites. The thermo-mechanical properties were characterized using dynamic mechanical analysis and heat distortion temperature (HDT). The results show that the modification of clay affected simultaneously the degree of PA6 matrix reinforcement, dispersion of the clay lamellas in the blend and size of the dispersed phase AES. The incorporation of different nanoclays increase the elastic modulus of all the ternary nanocomposites compared to the neat blend. An increase in the toughness is obtained only for systems with Cloisite®Na+. A significant increment in the storages modulus and HDT was observed by the incorporation of Cloisite®30B in the PA6/AES blends. <![CDATA[PVC micro and nanofibers produced via Solution Blow Spinning]]> Neste trabalho, micro e nanofibras de PVC foram obtidas pela técnica de Fiação por Sopro em Solução, uma técnica recentemente desenvolvida capaz de produzir micro e nanoestruturas poliméricas com velocidade alta e preços que rivalizam a eletrofiação. As micro e nanofibras produzidas neste trabalho, a partir de soluções de PVC em tetrahidrofurano tiveram diâmetros médios entre 217 nm e 2,5 μm. Os efeitos das condições de processamento foram avaliados, sendo que a concentração da solução polimérica foi o parâmetro de maior influência no diâmetro médio. Também foi observado que a estabilidade térmica das micro e nanofibras não foi afetada pela técnica de fiação por sopro em solução.<hr/>We obtained PVC micro- and nanofibers by Solution Blow Spinning, a recently developed technique capable of producing polymeric micro- and nanostructures with high speed as compared to other techniques such as electrospinning. The PVC fibers produced had an average diameter ranging from 217 nm to 2.5 µm, depending on the experimental conditions. We evaluated the effects of processing conditions and polymer concentration in solution had the most significant effect in fiber diameter. It was also observed that the thermal stability of the fibers was unaffected when compared to PVC films and powder.