Abstract in English:The ionic conductivity, thermal stability and lithium transference number have been investigated in composite polymer electrolytes (CPE) of poly(vinylidene fluoride - hexafluoropropylene) (PVDF-HFP) incorporating nano fillers of AlO[OH]n or gammaAl2O3, with LiClO4 as salt. The compatibility of the composite polymer electrolyte with lithium metal anode has also been studied. The effect of particle size on the compatibility of Li/ CPE/ Li symmetric cells has also been analyzed.
Abstract in English:Samples of epoxy resin (EP) based on the diglycidyl ether of bisphenol A (DGEBA), cured with nadic methyl anhydride (NMA) and mercaptan (CAPCURE 3-800), or amine-phenol (CAPCURE EH-30), respectively, SE 4 and SE 5, were prepared in the stoichiometric ratio determined by the supplier. The curing behaviour of the epoxy systems SE 4 and SE 5 was followed by DSC (Differential Scanning Calorimetry). These SE and their ingredients were analyzed using FTIR transmission techniques (KBr pellets, pyrolysis without control and controlled pyrolysis-FT-IR, the CONTROLPIR/FT-IR) for characterizing the curing agents (CA). The temperature range used for samples pyrolysis was found from TG (thermogravimetry). Thus, the FT-IR bands of liquid pyrolysate obtained by CONTROLPIR/FT-IR were evaluated, in comparison to the reference spectrum of CA. The characterization of CA was also possible, by the analysis of such SE with the TG/FT-IR technique.
Abstract in English:Successive aqueous (10 ºC, 25 ºC and 80 ºC) and alkaline (1M NaOH; 25 ºC) extractions of milled Parkinsonia aculeata endosperms gave rise to four galactomannan fractions. These extractions furnished viscous galactomannans with Man:Gal ratios ranging from 3.1:1; 3.7:1; 4.9:1 and 6.1:1 (P1, P2, P3 and P4, respectively). Fraction P1 was used for structural studies by using methylation analysis, periodate oxidation and 13C-NMR. It showed a linear backbone of beta(1->4) linked D-mannose units, to which single alpha(1->6)-linked D-galactose are attached. This galactomannan has Mw 775700 g/mol and intrinsic viscosity of 558 mL/g. The four fractions and the crude endosperm were treated with epichlorydrin and used as matrix for affinity chromatography. All columns tested showed ability to bind lectin samples. The efficiency is related to the degree and pattern of substitution of galactosyl units on the D-mannan backbone.
Abstract in English:Poly(phenylene sulfide) (PPS) is an engineering thermoplastic polymer that presents high temperature resistance (glass transition temperature around 85 ºC and melting point at 285 ºC). These properties combined with its mechanical properties and its high chemical resistance allows its use in technological applications such as molding resins and as matrix for structural thermoplastic composites. During the manufacture of thermoplastic composites, the polymer is exposed to repeated melting, quenching and crystallization processes. The properties of semicrystalline polymers, such as PPS, depend on its crystallization behavior. This work deals with the PPS crystallization kinetics under different thermal cycles. This study was performed under isothermal conditions in a differential scanning calorimetry (DSC), coupled to Perkin Elmer crystallization software referred to as Pyris Kinetics - Crystallization. The results were correlated with microscopic analyses carried out in a polarized light microscope, equipped with a controlled heating and cooling accessory. In this case, the experimental conditions were the same adopted for the DSC analyses. From the results, parameters could be established to be used in the composite manufacture.
Abstract in English:The introduction of epoxy groups into the main chain of elastomers has emerged as a promising alternative, considering the monitoring of polymer-filler interaction leading to changes in the properties of vulcanizates. The epoxidation reaction (in situ) was chosen to modify elastomers, such as polybutadiene (BR) and copolymer of styrene-butadiene-rubber (SBR), because it is a simple, easily controlled reaction, even considering the small epoxidation degree. The modification degree of the polymeric chain was studied with FT-IR and ¹H-NMR. The shift of the Tg to high temperatures with the increase of the epoxy group in the polymer chain was monitored through differential scanning calorimetry (DSC). An analysis of the dynamic modulus of the material in relation to its dependence on the amplitude and temperature was carried out. The interaction between epoxidized elastomeric matrix and silica as filler was extremely improved, even in the presence of very low content of epoxy groups into the polymer chain.
Abstract in English:The aim of this study was to impregnate the chelating agent 3,3-bis-N,N,bis-(carboxymethyl)aminomethyl-o-cresolsulfonephthalein in chitosan and to investigate the adsorption of Cu(II) ions. The chemical modification was confirmed by FTIR spectrometry, thermogravimetric analysis (TGA) and energy dispersive x-ray spectroscopy (EDX). The adsorption studies were carried out with Cu(II) ions in a batch process and were shown to be dependent on pH. The adsorption kinetics was tested using three models: pseudo first-order, pseudo second order and intraparticle diffusion. The experimental kinetics data were best fitted with the pseudo second-order model (R² = 0.999), which provided a rate constant, k2, of 1.21 x 10-3 g mg-1 min-1. The adsorption rate depended on the concentration of Cu(II) ions on the adsorbent surface and on the quantity of Cu(II) ions adsorbed at equilibrium. The Langmuir isotherm model provided the best fit for the equilibrium data in the concentration range investigated, with the maximum adsorption capacity being 81.0 mg of Cu(II) per gram of adsorbent, as obtained from the linear equation of the isotherm. Desorption tests revealed that around 90% of the adsorbed metal was removed, using EDTA solution as the eluent. This result suggests that the polymeric matrix can be reused.
Abstract in English:Composite films were studied as possible candidates for the central or support layer of synthetic paper in a multilayer structure. Recycled post-consumer polypropylene films were reinforced with inorganic fillers at various compositions and under several processing conditions, with the aim of optimizing the physical and mechanical properties of rigidity and low density. Three types of CaCO3, with and without surface treatment of the particles, were used, but only the treated ones were suitable for use in paper films. These samples were then used to analyze possible correlations of properties with composition and processing conditions, varying the CaCO3 particle size distribution and the film processing method, from casting extrusion (flat die) to blown-film extrusion (tubular die). An increase in film stiffness was observed as a function of CaCO3 content and a concentration of 30% CaCO3 was found to be best for the specific application. The flat films were stiffer than the tubular ones. The densities of all the composite films were considered high, compared to a pulp-based paper and a commercial synthetic paper. No significant effect on the physical-mechanical properties analyzed was observed when the CaCO3 particle size distribution was varied. Microcavities were found to form at the surface of flat films submitted to a bi-orientation process performed at laboratory scale; no other sample showed this surface morphology.
Abstract in English:The aim of this research is to study the biodegradation of a polyurethane derived from castor oil, which contains polyester segment in its molecular structure, thus becoming susceptible to the microorganisms attack. The biodegradation of polyurethane was tested in contact with microorganisms resulting from microbiological grease degrading agents, in appropriate liquid media, with a duration of 156 days. The study was done by using scanning electron microscopy (SEM), thermogravimetry (TG) and Fourier-transform infrared spectroscopy with accessory for attenuated total reflectance (FTIR-ATR). The results suggest that the degradation of polyurethane derived from castor oil occurs. TG curves are used in order to indicate the biodegradation, showing changes between the thermal behavior of the samples that were inoculated with microorganisms and control. In the FTIR-ATR spectra, there are detectable changes between the spectra of control and attacked specimens; this suggests that degradation occurs, with the decreased intensity of the absorption band at 1042 cm-1, corresponding to the esters links.
Abstract in Portuguese:Neste trabalho foram preparados nanocompósitos de polipropileno e montmorilonita organofílica comercial Cloisite 20A em concentrações de 2,5%, 5,0%, 7,5% e 10,0% e polipropileno graftizado com anidrido maleico como agente compatibilizante pela técnica de intercalação do fundido em extrusora de dupla rosca. Os materiais obtidos foram caracterizados por difração de raios x, ensaios de tração e impacto de acordo com as normas ASTM D638 e D256, respectivamente. Os resultados de difração de raios x indicaram a formação de nanocompósitos com estruturas parcialmente esfoliadas ou intercaladas, dependendo da composição, que proporcionaram aumento do módulo de elasticidade enquanto as propriedades de resistência ao impacto não foram satisfatórias.
Abstract in English:Nanocomposites of polypropylene and commercial montmorillonite organophilic Cloisite 20A containing 2.5%, 5%, 7.5% and 10% of clay with polypropylene-graft-maleic anhydride as coupling agent were prepared through the melt intercalation by twin-screw extruder. The materials were characterized by x-ray diffraction, tensile and impact properties according to ASTM D638 and D256 test methods, respectively. The x-ray diffraction results showed exfoliated or intercalated structures for different concentrations of the clay. The tensile modulus improved with the increase of the amount of the clay while the impact strength showed unsatisfactory results.
Abstract in Portuguese:O estudo da degradação in vitro de polímeros bioreabsorvíveis em soluções alcalinas vem sendo proposto nos últimos anos como alternativa aos estudos tradicionais feitos em tampão fosfato. Este trabalho descreve a degradação acelerada de poli(épsilon-caprolactona) (PCL) e poli(D,L-ácido láctico-co-ácido glicólico) (50/50) (PLGA50), polímeros biodegradáveis e bioreabsorvíveis, amplamente estudados em aplicações biomédicas. Amostras foram preparadas pelo método de fusão seguido de injeção em molde cilíndrico (2 mm diâmetro), a 160 ºC, e submetidas à degradação em soluções de NaOH em pH 12, 13 e 13,7 a 37 ºC. Por meio da caracterização da variação da massa, morfologia e propriedades térmicas, por calorimetria exploratória diferencial, os resultados mostraram que as amostras de PCL são mais estáveis quando comparadas às de PLGA50. Pela taxa de variação das propriedades térmicas foi possível extrapolá-las em função do tempo em pH fisiológico, 7,4. Validado, o estudo da degradação acelerada em meio alcalino mostrou-se como uma técnica útil e de baixo custo para avaliar o comportamento em curtos períodos de degradação.
Abstract in English:The in vitro degradation studies of bioresorbable polymers in alkaline medium have been proposed as alternative to the traditional studies in phosphate buffer solution. This work describes the study of the accelerated degradation of the poly(epsilon-caprolactone) (PCL) and poly(D,L-lactic acid lactic-co-glycolic acid) (50/50) (PLGA50), a biodegradable and bioresorbable polymer widely studied for biomedical applications. Samples were prepared with the melt compression method in a cylindrical mold (2 mm diameter), at 160 ºC, and submitted to the degradation in solutions of NaOH in pH 12, 13 and 13.7 at 37 ºC. The results from the characterization of the mass variation, morphology and thermal properties, using differential scanning calorimetry, showed that the samples of PCL are stable compared to the one of PLGA50. The thermal properties could be extrapolated as a function of time in the physiological pH, 7.4. Once validated, the accelerate study of degradation in alkaline medium proved to be a useful, low cost technique for evaluation of samples with short degradation times.
Abstract in Portuguese:Devido a suas excelentes propriedades mecânicas o polietileno linear de baixa densidade, PELBD, tem ganhado cada vez mais importância na indústria de embalagens. Essas propriedades são resultado de sua estrutura molecular, da existência de ramificações curtas, SCB, e da distribuição dessas ramificações, DSCB. Junto com o peso molecular, PM, e sua distribuição, DPM, as ramificações curtas também afetam o processo de sopro de filmes influenciando na solidificação do filme até a linha de neve, já que a cinética de cristalização é dependente da distribuição destas ramificações. Assim, este trabalho teve como objetivo verificar a influência da DSCB do PELBD nas propriedades reológicas e óticas de filmes tubulares. Para isso, três PELBD foram escolhidos; dois sintetizados com catalisador Ziegler-Natta e um com catalisador metaloceno, de peso molecular ponderal médio, Mw, similar e DSCB diferentes. Observou-se que a DSCB exerce influência nas propriedades reológicas que refletem a elasticidade do material como a primeira diferença de tensões normais N1, o módulo de armazenamento G'(<FONT FACE=Symbol>w</font>), e a deformação recuperável gamar; entretanto na viscosidade em função da taxa de cisalhamento eta(gama), e no módulo de perda G"(ômega), a diferença nessa distribuição não foi percebida. Observou-se também que quanto maior a deformação recuperável dos PELBD, menores foram as estruturas cristalinas formadas o que diminuiu a opacidade dos filmes. Porém essa proporcionalidade manteve-se até uma determinada gamar mínima, acima da qual a fratura do fundido se sobrepôs à recuperação da deformação e a opacidade voltou a aumentar.
Abstract in English:Linear low-density polyethylene, LLDPE, has increased its market share in the packaging industry due to its excellent mechanical properties. These properties are the result of its molecular structure due to its short chain branching, SCB, and their distribution, DSCB. Together with the molecular weight and the distribution of molecular weights, the SCB affects the blown film process because it interferes in the film solidification and crystallization kinetics up to the freezing line. The objective of this work was to verify the influence of the DSCB of LLDPE in the rheological and optical properties of blown films. Three LLDPE, synthesized with Ziegler-Natta and metallocene catalysts, were studied, all with similar weight average molecular weight, Mw, but with different DSCB. It was observed that the DSCB influenced the rheological properties that reflect the material elasticity, such as the first normal tension difference, N1(<FONT FACE=Symbol>g</font>), the storage modulus G'(w) and the recoverable strain gammar; however, the rheological properties that reflect the viscosity, such as the shear viscosity eta(gamma) and the loss modulus G"(w), were not affected. In addition, the higher the gammar of the LLDPE, the lower the crystalline structures of the films, which decreased their opacity. However this proportionality was kept up to a given value of gammar above which the melt fracture dominated the recoverable strain and the opacity increased again.
Abstract in Portuguese:O objetivo deste trabalho é a caracterização do AES, um copolímero de enxertia de poli(estireno-co-acrilonitrila), SAN, em poli(etileno-co-propileno-co-dieno), EPDM. Para tanto, o AES foi submetido à extração seletiva de seus componentes: o SAN livre, o EDPM livre, e o copolímero de enxertia EPDM-g-SAN. O AES e suas frações foram caracterizados por espectroscopia de infravermelho, análise elementar, calorimetria diferencial de varredura e ressonância magnética nuclear, RMN¹H e RMN13C. O AES analisado apresenta a seguinte composição em massa: 65% de EPDM-g-SAN, 13% de EPDM livre e 22% de SAN livre. O EPDM apresenta 69,8% em massa de etileno, 26,5% em massa de propileno e 4,6% em massa do dieno, 2-etilideno-5-norboneno, ENB. O SAN apresenta razão em massa acrilonitrila/estireno de 28/72 e distribuição randômica de comonômeros de estireno e acrilonitrila. Estes resultados são concordantes com a composição do AES fornecida pelo fabricante, indicando que a metodologia proposta é adequada.
Abstract in English:This work aims the characterization of AES, a graft copolymer based on poly(styrene-co-acrylonitrile), SAN, and poly(etyhlene-co-propylene-co-diene), EPDM. AES was submitted to selective extraction of its components: free SAN, EPDM chains and the graft copolymer EPDM-g-SAN. AES and its fractions were characterized by infrared spectroscopy, elemental analysis, differential scanning calorimetry, 13C and ¹H nuclear magnetic resonance. The AES has 65 wt % of EPDM-g-SAN, 13 wt % of free EPDM and 22 wt % of free SAN. EPDM has 69.8 wt % of ethylene, 26.5 wt % of propylene and 4.6 wt % of diene, 2-ethylidene-5-norbonene ENB. SAN presents acrylonitrile/styrene mass ratio of 28/72 and a random distribution of acrylonitrile and styrene comonomers. These results are in agreement with the composition reported by the AES supplier, indicating that the proposed methodology is adequate.
Abstract in Portuguese:Este artigo busca analisar a relação existente entre o grau de gelificação de compostos de PVC rígido (U-PVC) durante seu processamento e as propriedades mecânicas finais dos produtos obtidos através do processo de extrusão de tubos. Para tanto, a morfologia das resinas de PVC é analisada a fim de se entender seu desenvolvimento ao longo da extrusão e entender sua influência na gelificação já que o desempenho do produto dependerá dessa influência. O desenvolvimento morfológico, devido às condições de processamento e ambiente termo-mecânico, bem como alguns testes como microscopia eletrônica de varredura para monitorar esse desenvolvimento são descritos. O grau de gelificação e sua quantificação são analisados utilizando reometrias de torque, rotacional e capilar, utilizando análises térmicas (DSC) e utilizando imersão em solvente (cloreto de metileno).
Abstract in English:This paper analyses the relation between the degree of gelation of rigid unplasticised PVC compounds (U-PVC) and the mechanical properties of final products made of them. The morphology of PVC resins is analyzed in order to understand its development during the extrusion process and the influence in the gelation process, once the performance of the final product depends of it. The morphological development, the processing conditions, the thermal-mechanical environment and some techniques for its determination, such as scanning electron microscopy, are described. The degree of gelation and its quantification are determined using torque, rotational and capillary rheometry, differential scanning calorimetry (DSC) and solvent immersion (dichloromethane).