The use of a polypyrrole (PPy) is described as an efficient extraction phase for disposable pipette extraction (DPX), in a fast and ruggedized analytical method for simultaneous determination of 18 organic micro-pollutants in water using gas chromatography-mass spectrometry (GC-MS). The DPX-blank pipettes were filled with PPy, a material produced through the chemical polymerization of PPy using iron(III) chloride hexahydrate. The optimized conditions were 5 extraction cycles with 600 µL of sample, adjusted to pH 9, and desorption with 150 µL of ethyl acetate using 7 cycles with the same aliquot. The calibration curves resulted in determination coefficient (R2) higher than 0.9963, the limit of detection (LOD) ranged from 0.4 to 1.5 µg L−1, and the limit of quantification (LOQ) were from 1.4 to 5.0 µg L−1. Excellent results were obtained for repeatability (2.3 to 15%, for 5 µg L−1) and intermediate precision, varying the day of analyses (3.9 to 15.5%) and the pipette tip (3.4 to 22.4%). The analyte recovery ranged from 75.4 to 115.0% for river water, and from 74.9 to 116.2% for tap water, in three different levels of concentration. The DPX-GC-MS method with PPy was successfully applied to determine the 18 analytes in river and tap water from the cities of Joinville and Florianópolis, Santa Catarina, Brazil.

A novel pressure sensing material composed of poly (butylene adipate-co-terephthalate) (PBAT) and montmorillonite-polypyrrole (Mt-PPy) was prepared using melt mixing and injection molding. The structure and properties of the PBAT/Mt-PPy composites were evaluated and compared with those of the PBAT/PPy blends. The PBAT/Mt-PPy displays a very sharp insulator-conductor transition and its percolation threshold was reached at 6.5 wt% of Mt-PPy, which was lower than that for PBAT/PPy (11.0 wt% of PPy). The transmission electron microscopy analysis shows that Mt-PPy displays a high aspect ratio and was better distributed and dispersed into PBAT compared to PPy. PBAT/Mt-PPy exhibits a decrease in the electrical resistivity with an applied compressive stress due to the formation of new conducting pathways. The electromechanical response was dependent on Mt-PPy and the maximum sensitivity was observed for the composite containing 10 wt% of Mt-PPy. In this system, the electrical resistivity drops from 9 x 106 to 2 x 106 Ω cm when a compressive stress of 0.25 MPa was applied. The electrical resistivity changes with applied compressive stress, the reproducibility and the reversibility makes PBAT/Mt-PPy a suitable material for the development of pressure sensors.

In this study, composites based on polyurethane (PU) derived from castor oil and montmorillonite/polypyrrole doped with dodecylbenzenesulfonic acid (MMt-PPy.DBSA) were developed. In order to investigate the potential use of these materials for electromagnetic shielding applications, the electrical and mechanical properties of PU/MMt-PPy.DBSA composites were determined and compared with composites containing neat PPy.DBSA. The electrical conductivity of PU/MMt-PPy.DBSA composites was found to be higher than those for PU/PPy.DBSA with a similar filler content. Additionally, with a higher conductive additive content, significant increases in the tensile stress (σ) and elastic modulus (E) were observed, suggesting that MMt-PPy.DBSA acts as reinforcing agent for the PU matrix. The electromagnetic interference shielding effectiveness (EMI SE) of composites is mainly dependent on the morphology and filler content. The PU/MMt-PPy.DBSA composite containing 25 wt % of MMt-PPy.DBSA showed a maximum EMI SE of -21 dB, which is similar to the value required for commercial applications (-20 dB). The results revealed that PU/MMt-PPy.DBSA composites are promising materials for electromagnetic shielding applications.

In this study, the relationship between structure and mechanical properties of aged PBT composite was investigated. Short glass fiber reinforced PBT composites were subjected to aging tests in environments typically found in hermetic compressors. Diffusion kinetics were addressed by a periodic control of samples weight, and samples aged in oil presented mass variation of 1.2-1.6%, depending on test temperature. Most diffusion curves followed Fickian behavior, and the diffusion coefficient for each condition was obtained. Aging effect was investigated by 3-point bending tests, where samples aged at 180°C presented a significant reduction in all evaluated properties. Control environment induced minor variations, supposedly related to physical aging and increase in crystallinity. Imaging analyses through scanning electronic microscopy (SEM) technique allowed observation of the predominant fracture mechanism. Aged samples presented few or no localized plastic deformation at all, which is in accordance with the lower strain observed in mechanical tests. Differential scanning calorimetry (DSC) analyses proved degree of crystallinity increase for all aged samples, depending mainly on temperature of exposure. Infrared (FTIR) analysis proved the presence of oil absorbed in PBT chemical structure, and it was proposed a method for comparing degree of crystallinity, based on the absorbance bands ratio A0(1458 cm-1)/A0(956 cm-1).

O presente trabalho visa investigar a viabilidade de utilização de fibras naturais de sílica amorfa (FNSA) como agente de reforço em polímeros de engenharia, assim como avaliar o seu potencial como alternativa às fibras de vidro curtas em aplicações industriais. Diferentes modificações na química de superfície dessas fibras foram avaliadas buscando melhorar a adesão na interface entre fibras e matriz, e consequentemente, melhorar as propriedades mecânicas do compósito. As modificações superficiais das FNSA foram realizadas através de agentes de acoplamento do tipo silano, providos com funções orgânicas distintas. O PBT foi selecionado como matriz devido a sua conhecida facilidade de processamento, mesmo após a incorporação de grandes quantidades de aditivos. A modificação das FNSA foi avaliada a partir da análise termogravimétrica acoplada à espectroscopia no infravermelho com transformada de Fourier. A resistência mecânica e fratura dos compósitos foi investigada por ensaios de tração e microscopia eletrônica de varredura. Finalmente, obtiveram-se compósitos com fibras modificadas com resistência à tração 40% superior ao material base puro.

This work aims to investigate the viability of natural amorphous silicate short fibers (FNSA) as reinforcing agent of thermoplastic engineering polymers, and their possible use as an alternative to short glass fibers in industrial applications. Different surface modifications were performed in order to improve interface adhesion between the matrix and FNSA, and consequently improve mechanical properties. The surface treatments of FNSA were applied with silane coupling agents provided with different organofunctional groups. PBT was chosen as matrix due to its easy manufacturing process even after incorporation of large quantities of additives. The surface chemistry after modification was evaluated through thermogravimetric analyses coupled to a Fourier transformed infrared spectroscopy equipment. Mechanical resistance and composite fracture were investigated through tensile tests and image analyses by scanning electron microscopy. Finally, the tensile strength of modified fibers reinforced PBT was 40% higher than neat PBT.

Nanocompósitos de montmorilonita/polipirrol (MMT/PPy) foram preparados a partir da polimerização in situ do pirrol na presença de argila, bentonita sódica natural, (MMT-Na+) em solução aquosa com ou sem surfactante aniônico, dodecil sulfato de sódio (SDS), utilizando-se o cloreto de ferro (III) hexahidratado (FeCl3.6H2O), como oxidante. A estrutura e propriedades dos nanocompósitos obtidos pela polimerização in situ do pirrol na presença de SDS (MMT/PPy.SDS) e sem surfactante (MMT/PPy) foram avaliadas e comparadas a partir da espectroscopia de infravermelho com transformada de Fourier (FTIR), difração de raios X (DRX), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (MET), análise termogravimétrica (TG) e método padrão quatro pontas. Os difratogramas dos nanocompósitos revelaram que o espaçamento basal d001 da MMT (1,42 nm) foi alterado para valores maiores, indicando a intercalação do PPy na MMT para ambos os nanocompósitos obtidos. Os difratogramas e as imagens de MET e MEV dos nanocompósitos de MMT/PPy.SDS confirmaram que a presença do SDS na reação promoveu, além da intercalação, esfoliação parcial da argila. Os nanocompósitos MMT/PPy.SDS apresentaram condutividade elétrica (9,50 S/cm) maior do que o nanocompósito de MMT/PPy (4,44 S/cm). A presença da argila melhorou de forma significativa a estabilidade térmica do PPy.

Montmorillonite/polypyrrole (MMT/PPy) nanocomposites were prepared by the in situ polymerization of pyrrole in the presence of clay, natural sodium bentonite, (MMT-Na+) in aqueous solutions with or without an anionic surfactant, sodium dodecyl sulfate (SDS), using Iron (III) chloride hexahydrate (FeCl3.6H2O) as oxidant. The structure and properties of the nanocomposites obtained by the in situ polymerization of pyrrole in the presence of SDS (MMT/PPy.SDS) and without surfactant (MMT/PPy) were compared and evaluated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis and the four-point probe method. The XRD patterns of the MMT/PPy composites shows that the d001 spacing in MMT (1.42 nm) was changed to higher values, indicating the intercalation of PPy on MMT for both nanocomposites. The XRD pattern, SEM and TEM images of the MMT/PPy.SDS nanocomposites confirmed that the presence of SDS in the reaction medium promoted, beyond intercalation, the partial exfoliation of the clay. The MMT/PPy.SDS nanocomposites showed electrical conductivity (9.50 S/cm) higher than the MMT/PPy nanocomposites (4.44 S/cm). The presence of the clay significantly improved the thermal stability of PPy.

The aim of this study was to obtain and evaluate the electrical, thermal and mechanical properties of iron oxide-filled castor oil polyurethane (PU/Fe2O3). The iron oxide used in this study was a residue derived from the steel pickling process of a Brazilian steel rolling industry. Polymeric composites with different iron oxide volume fractions (2.5, 5.0, 7.5, 10.0 and 12.5%) were prepared through the casting process followed by compression molding at room temperature. The composites were analyzed by FTIR, XRD and densities, tensile strength, Young's modulus, electrical and thermal conductivities measurements. By increasing the iron oxide content, the apparent density, tensile strength, Young's modulus and electrical conductivity values of the composites were also increased. The iron oxide additions did not change significantly the value of thermal conductivity (from 0.191 W.mK-1 for PU up to 0.340 W.mK-1 for PU enriched with 12.5% v/v of iron oxide). Thus, even at the higher iron oxide concentration, the compounds as well as the pure polyurethane can be classified as thermal insulators.

Neste trabalho foi avaliada a influência do tratamento químico de fibras vegetais nas propriedades mecânicas e dinâmico-mecânicas de resina epóxi reforçada com tecidos de fibras de juta. As fibras foram modificadas a partir de solução de hidróxido de sódio, e caracterizadas por microscopia eletrônica de varredura (MEV), espectrometria no infravermelho com transformada de Fourier (FTIR) e resistência à tração. As análises de FTIR e MEV evidenciaram, respectivamente, que o tratamento alcalino promoveu a remoção parcial da hemicelulose e modificou a morfologia das fibras de juta. Amostras dos compósitos com fibras tratadas e não tratadas foram confeccionadas a partir da laminação manual seguida da moldagem por compressão. Compósitos com fibras tratadas apresentaram propriedades mecânicas e módulo de armazenamento maiores do que as da resina epóxi sem reforço e compósitos com fibras sem tratamento. As micrografias de microscopia eletrônica de varredura (MEV) revelaram que compósitos com fibras tratadas possuem menor quantidade de vazios e menor quantidade de pull-out, sugerindo maior adesão com a matriz polimérica do que os compósitos com fibras sem tratamento.

This study was aimed at evaluating the efficiency of chemical treatment on the dynamic mechanical and mechanical properties of composite materials with jute fibers and epoxy matrix resin. The surfaces of the jute fibers were modified by contact with sodium hydroxide solutions, and characterized through scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and tensile strength testing. The FTIR and SEM analysis evidenced that the alkaline treatment promoted removal of the hemicellulose and modification in the morphology of the jute fibers, respectively. Polymeric composites with untreated and treated jute fiber were prepared through hand lay-up process followed by compression molding. The treated jute fiber composites displayed higher mechanical properties and storage modulus values than the epoxy resin and untreated fiber composites. The scanning electron micrographs (SEM) revealed that treated jute fiber composites have less voids and pull-out, suggesting a better adhesion with the polymeric matrix than untreated fiber composites.

Neste trabalho, três derivados do poli(éter éter cetona) [PEEK] foram preparados em suspensão por meio da nitração, redução para o grupo amino e redução da carbonila. Os polímeros modificados foram caracterizados por espectroscopia de infravermelho (FTIR), Ressonância Magnética Nuclear (NMR), análise termogravimétrica (TGA) e apresentaram características interessantes para a preparação de membranas e compósitos, tais como, basicidade e solubilidade em solventes orgânicos, como DMF.

In this study, three derivatives of poly(ether ether ketone) [PEEK] were prepared in suspension by nitration (NO2-PEEK), reduction to the amino group (NH2-PEEK) and carbonyl reduction (PEEK-OH). These modified polymers were characterized by NMR, IR spectroscopy and thermogravimetric analysis. They showed interesting characteristics, such as, basicity and higher solubility in organic solvents, like DMF, for use as membranes and composites in different applications.

Biossensores têm a função de detectar e analisar tanto quantitativa como qualitativamente a presença de uma certa molécula em um determinado meio, isto com resposta em tempo real e sem etapas intermediárias de processo. Para isso, o biossensor possui sempre em seu conjunto um sistema de reconhecimento biológico que o diferencia de qualquer outro tipo de sensor. O objetivo deste trabalho foi desenvolver hidrogéis condutores a partir da combinação de polianilina com hidrogel poli(metacrilato de hidroxietila) e avaliar alguns aspectos associados à possível utilização deste como base de um biossensor capaz de detectar a presença de frações tóxicas do antígeno do veneno do escorpião Tytius Serrulatus. Hidrogéis condutores foram sintetizados a partir da mistura, em diferentes proporções, de polianilina e poli(metacrilato de hidroxietila) em um solvente comum. A condutividade elétrica (método de quatro pontas), capacidade de inchamento e morfologia (microscopia eletrônica de varredura) foram avaliadas para blendas com diferentes composições. Antígenos relativos ao veneno do escorpião Tytius Serrulatus foram incorporados às blendas condutoras a partir do inchamento dos hidrogéis por soluções aquosas contendo as moléculas de interesse. A imobilização e bioatividade das biomacromoléculas nos hidrogéis foram constatadas através de ensaio imunoabsorvente ELISA cujos resultados foram avaliados por espectroscopia na região do ultravioleta-vísivel. Os resultados mostraram que a incorporação de baixos conteúdos de Pani (20% em massa) em hidrogéis de poli(metacrilato de hidroxietila) foi suficiente para a produção de materiais com elevada condutividade elétrica e grande capacidade de inchamento. Moléculas associadas ao veneno do escorpião Tytius Serrulatus foram imobilizadas com sucesso nos hidrogéis condutores e mantiveram suas capacidades funcionais.

Biosensors can detect and analyze quantitatively and qualitatively the presence of a given molecule in a specific environment. Biosensors always have a biological recognition system that distinguishes them from any other kind of sensor. The goals of this work were to develop conductive hydrogels from the combination of polyaniline and poly(hydroxyethyl methacrylate) and to evaluate some important aspects related to the possibility of using these materials as matrices in biosensors that would detect toxic fractions of antigens associated with the venom of the Tytius Serrulatus scorpion. Different conductive blends from poly(hydroxyethyl methacrylate) and polyaniline were produced by dissolving the polymers in a common solvent. The electrical conductivity, morphology and swelling ability were measured the four-probe measuring system, scanning electron microscopy and weight gain in water, respectively. Immobilization and bioactivity of molecules associated with the venom of the Tytius Serrulatus scorpion were evaluated by combining the ELISA immunoassay method and ultraviolet-visible spectroscopy. The results showed that even low concentrations of polyaniline led to high values of electrical conductivity and swelling. The biological tests indicated that the immobilization and bioactivity of the biomacromolecules associated with the venom of the Tytius Serrulatus scorpion were successfully achieved within the conductive hydrogel.

Neste trabalho foram estudadas as propriedades micro e macroscópicas de misturas físicas binárias de poliamida 6 [PA6] com copolímero poli(etileno-co-propileno-co-dieno) [EPDM] e em presença de pequenas quantidades de EPDM ou EPM enxertados com anidrido maleico, atuando como agentes compatibilizantes. Os componentes puros (poliamida 6 e EPDM) e as blendas poliméricas em diferentes composições foram analisados por calorimetria diferencial de varredura (DSC) e espectroscopia de infravermelho (FTIR). Os resultados indicaram a imiscibilidade dos componentes da mistura em toda a faixa de composição estudada. A utilização das técnicas de análise elementar, microscopia eletrônica de varredura e propriedades mecânicas permitiu avaliar a homogeneidade da mistura, a redução do tamanho dos domínios do elastômero e o aumento da força de impacto da matriz de PA6 com a adição do agente compatibilizante à mistura binária de PA6/EPDM.

This study describes the micro- and macroscopic properties of polyamide 6 (PA6) and ethylene /propylene/diene copolymer (EPDM) blends, and the effects from small quantities of EPDM or EPM grafted with maleic anhydride in this polymer mixture. The components and polymer blends at different compositions were analyzed by differential scanning calorimeter (DSC) and infrared spectroscopy (FTIR). The results suggest immiscible mixture in all ranges of the blend's compositions. Scanning electron microscopy (SEM) micrographs of the blends indicated that the size of rubber aggregates decreases as the functionalized elastomer (EPDM-g-MA or EPM-g-MA) is added to the PA6/EPDM mixture, and the impact strength of the PA6 matrix increases significantly.

Misturas elastoméricas condutoras de eletricidade envolvendo copolímero tribloco poli(estireno-b-butadieno-b-estireno) (SBS) e polianilina dopada com ácido dodecilbenzenosulfônico (Pani.DBSA) foram obtidas por polimerização "in situ". Os filmes obtidos por moldagem por compressão mostraram baixo limiar de percolação, apresentando valores de condutividade semelhantes aos encontrados para o polímero condutor puro com cerca de 20 % em massa de Pani.DBSA. A caracterização das misturas por análise termodinâmico-mecânica (DMTA) evidenciou uma ligeira interação da Pani.DBSA com ambas fases do copolímero SBS. Na região borrachosa, o módulo da mistura aumenta com o aumento do conteúdo de Pani. No entanto, existe uma progressiva queda no fator de amortecimento ("damping") com o aumento da concentração de Pani. A energia de ativação, Ea, do processo de transição vítreo-borrachoso de ambas fases do SBS foi calculada, utilizando a equação de Arrhenius com os dados obtidos tanto por DMTA como por análise termodielétrica (DETA). A caracterização dielétrica não proporcionou informações a respeito da localização da Pani.DBSA na matriz de SBS. No entanto, observou-se o fenômeno de polarização interfacial entre a Pani e o SBS. Uma morfologia do tipo microtubos foi observada para Pani.DBSA na mistura SBS/Pani.DBSA, utilizando-se a técnica de microscopia eletrônica de varredura.

Conducting rubbery blends of styrene-butadiene-styrene (SBS) triblock copolymer and polyaniline doped with dodecylbenzenesulfonic acid (Pani.DBSA) were produced by "in situ" polymerization. The films obtained by compression-molding display low percolation threshold with conductivity values similar to that found for pure Pani.DBSA with only 20 wt% of Pani.DBSA in the SBS/Pani.DBSA blend. The dynamic-mechanical characterization demonstrated that PAni.DBSA presents a slight interaction with both phases of the SBS copolymer. In the rubbery region, the modulus of the blend increases with the increase of the Pani content. The values of Tg of the polybutadiene block were not affected by the addition of Pani. However, there is a progressive drop of the damping values with the increase of Pani concentration. The activation energy Ea for the glass transition process for both SBS phases was calculated from DMTA and DETA results, using the Arrhenius equation. From DMTA data, it is found that Ea corresponding to the PB segment of SBS presents a slight increase with the addition of Pani.DBSA, whereas the Ea corresponding to the PS segment increases substantially with the presence of Pani.DBSA. These results were also confirmed by DETA. The dielectric characterization does not provide conclusive information concerning the preferential localization of Pani.DBSA, but gives some information about interfacial polarization between the Pani and SBS in this blend. The formation of microtubules was observed by scanning electron microscopy in the SBS/Pani.DBSA blends.

Compósitos condutores de eletricidade envolvendo polianilina e resina epoxídica foram preparados utilizando-se o método da polimerização in situ. O método consiste da polimerização em emulsão da anilina na presença da resina epoxídica. Ácido dodecilbenzenossulfônico foi utilizado como agente dopante, que age também como surfactante da polimerização em emulsão. A condutividade elétrica do sistema Pani/resina epoxídica alcançou valores tão altos quanto 2 x 10-3 S/cm, com uma concentração de Pani correspondente a 7% em peso. O conteúdo de Pani na mistura foi determinado por análise elementar. O efeito do método de cura da resina epoxídica na condutividade elétrica, temperatura de transição vítrea e propriedades mecânicas do sistema foi também investigado.

The conductive composites of polyaniline (Pani) and epoxy resin were prepared by polymerization of aniline in the presence of epoxy resin, using a direct, one step in situ polymerization method. The polymerization of aniline was performed in an emulsion system comprising water and toluene containing epoxy resin in the presence of dodecylbenzene sulfonic acid, which acts as surfactant and a dopant for Pani. The electrical conductivity of Pani/ epoxy resin reached values as high as 2 x 10-3 S/cm at a Pani content corresponding of 7 wt% of Pani. The Pani content in the mixtures was calculated by means of elemental analysis. The relationships between glass transition temperature (Tg) and Pani.DBSA content obtained by two different cured methods were also investigated.

Nos últimos anos tem sido estudada a modificação de polímeros com grupos funcionais específicos, com o objetivo de obter blendas compatíveis com propriedades macroscópicas desejáveis. Neste trabalho foi determinado a percentagem do enxerto do EPDM com anidrido maleico (AM), em solução, utilizando peróxido de benzoila como iniciador. As condições de enxerto foram estudadas em função do tempo de reação e da quantidade de anidrido maleico. Para a determinação quantitativa do AM enxertado na cadeia do EPDM foi utilizado o método de espectroscopia de infravermelho, sendo o procedimento discutido em detalhes.

Several attempts have been made to compatibilize immiscible blends by introducing suitably-chosen polymer additives. This work studies the EPDM elastomer, chemically modified with maleic anhydride (MA), through reaction in solution of EPDM and MA, using dibenzoyl peroxide as an initiator. The best conditions for obtaining the maximum grafting were studied at different times and percentage weights of maleic anhydride. The evaluation of MA grafting onto EPDM was determined with multiple internal reflectance infrared spectroscopy as discussed in detail.