Preparação e caracterização de complexos multicomponentes contendo ciclodextrinas com metotrexato

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Efeito de adições poliméricas na aderência de pastas de cimento a tubos metálicos após ciclagem térmica

Thermal recovery methods, especially steam injection, have been used to produce heavy oils. However, these methods imply that the metallic casing-cement sheath interface is submitted to thermal cycling. As a consequence, cracking may develop due to the thermal expansion mismatch of such materials, which allows the flow of oil and gas through the cement sheath, with environmental and economical consequences. It is therefore important to anticipate interfacial discontinuities that may arise upon Thermal recovery. The present study reports a simple alternative method to measure the shear strength of casing-sheath interfaces using pushthrough geometry, applied to polymer-containing hardened cement slurries. Polyurethane and recycled tire rubber were added to Portland-bases slurries to improve the fracture energy of intrinsically brittle cement. Samples consisting of metallic casing sections surrounded by hardened polymer-cement composites were prepared and mechanically tested. The effect of thermal cycles was investigated to simulate temperature conditions encountered in steam injection recovery. The results showed that the addition of polyurethane significantly improved the shear strength of the casing-sheath interface. The strength values obtained adding 10% BWOC of polyurethane to a Portland-base slurry more than doubled with respect to that of polyurethane-free slurries. Therefore, the use of polyurethane significantly contributes to reduce the damage caused by thermal cycling to cement sheath, improving the safety conditions of oil wells and the recovery of heavy oils

Estudo do aproveitamento de resíduo de gesso como carga para compósito com matriz de resina expansiva de mamona

In the execution of civil engineering works, either by wasting during the coating of wall or demolition of gypsum walls, the generation of the gypsum waste involves serious environmental concerns. These concerns are increased by the high demand of this raw material in the sector and by the difficulties of proper disposal byproduct generated. In the search for alternatives to minimize this problem, many research works are being conducted, giving emphasis in using gypsum waste as fillers in composites materials in order to improve the acoustic, thermal and mechanical performances. Through empirical testing, it was observed that the crystallization water contained in the residue (CaSO4.2H2O) could act like primary agent in the expanding of the polyurethane foam. Considering that polyurethane produced from vegetable oils are biodegradable synthetic polymers and that are admittedly to represent an alternative to petrochemical synthetic polyurethane, this research consist an analysis of the thermal behavior of a composite whose matrix obtained from a resin derived from the expansive castor oil seed, with loads of 4%, 8%, 12% and 16% of gypsum waste replacing to the polyol prepolymer blend. Contributors to this analysis: a characterization of the raw material through analysis of spectroscopy by Fourier transform infrared (FTIR), chemical analysis by X-Ray Fluorescence (XRF) and mineralogical analysis by X Ray Diffraction (XRD), complemented by thermo gravimetric analysis (TGA). In order to evaluate the thermo physical properties and thermal behavior of the composites manufactured in die closed with expansion contained, were also carried tests to determine the percentage of open pore volume using a gas pycnometer, scanning electronic microscopy (SEM), in addition to testing of flammability and the resistance to contact with hot surfaces. Through the analysis of the results, it appears that it is possible to produce a new material, which few changes in their thermo physical properties and thermal performance, promotes significant changes and attractive to the environment

Eletrofiação e caracterização de membranas biopoliméricas a base de quitosana extraídas dos exoesqueletos de crustáceos

Chitin and chitosan are nontoxic, biodegradable and biocompatible polymers produced by renewable natural sources with applications in diverse areas such as: agriculture, textile, pharmaceutical, cosmetics and biomaterials, such as gels, films and other polymeric membranes. Both have attracted greater interest of scientists and researchers as functional polymeric materials. In this context, the objective of this study was to take advantage of the waste of shrimp (Litopenaeus vannamei and Aristeus antennatus) and crabs (Ucides cordatus) from fairs, beach huts and restaurant in Natal/RN for the extraction of chitin and chitosan for the production of membranes by electrospinning process. The extraction was made through demineralization, deproteinization, deodorization and deacetylation. Morphological analyzes (SEM and XRD), Thermal analysis (TG and DTG), Spectroscopy in the Region of the Infrared with Transformed of Fourier (FTIR) analysis Calorimetry Differential Scanning (DSC) and mechanical tests for traction were performed. In (XRD) the semicrystalline structure of chitosan can be verified while the chitin had higher crystallinity. In the thermal analysis showed a dehydration process followed by decomposition, with similar behavior of carbonized material. Chitosan showed temperature of maximum degradation lower than chitin. In the analysis by Differential Scanning Calorimetry (DSC) the curves were coherent to the thermal events of the chitosan membranes. The results obtained with (DD) for chitosan extracted from Litopenaeus vannamei and Aristeus antennatus shrimp were (80.36 and 71.00%) and Ucides cordatus crabs was 74.65%. It can be observed that, with 70:30 solutions (v/v) (TFA/DCM), 60 and 90% CH3COOH, occurred better facilitate the formation of membranes, while 100:00 (v/v) (TFA/DCM) had formation of agglomerates. In relation to the monofilaments diameters of the chitosan membranes, it was noted that the capillary-collector distance of 10 cm and tensions of 25 and 30 kV contributed to the reduction of the diameters of membranes. It was found that the Young s modulus decreases with increasing concentration of chitosan in the membranes. 90% CH3COOH contributed to the increase in the deformation resulting in more flexible material. The membranes with 5% chitosan 70:30 (v/v) (TFA/DCM) had higher tensile strength

Desenvolvimento de nanocompósito (hidroxiapatita/ poliuretano) pela gelação (gelling) de poli ( álcool vinílico) (PVA) para remoção de metais pesados

Removing microcontaminants from effluents is a challenge today, because of its high cost and low efficiency, especially in the treatment of effluents containing heavy metals. An alternative that has emerged is the use of biodegradable nanocomposites, which exhibit good removal and recovery performances, in addition to its low cost. With this in mind, the present study aimed to develop and characterize a nanocomposite based on hydroxyapatite (HAP), polyurethane (PU) and polyvinyl alcohol (PVA) for removing heavy metals. Thus, the research was conducted in several steps: i)- Physico-chemical and microbiological hospital effluent characterization; ii)- Production of hydroxyapatite by aqueous precipitation technique, and their characterization; iii)- Production of the nanocomposite in which the hydroxyapatite was added to the polyurethane prepolymers and then the polyvinyl alcohol/hydroxyapatite film was produced; iv)- Polyvinyl composite without film PU/HAp was also produced in the proportions of 20 and 40% HAp; v)- The composites was characterized by the techniques of XRD, FTIR, SEM / EDS, BET, Zeta Potential and TGA; vi)- The sisal and coconut fibres were washed and dried for comparative tests of adsorption; vii)- Adsorption tests for evaluating the removal of heavy metals (nickel and cadmium). Initial screening adsorption capacity (HAp; PU/HAp - 20 and 40%; PU / HAp / PVA), kinetic studies of adsorption of Cd (II) by HAp; multifactorial design analysis (factorial design) for identifying the most important variables in the adsorption of Cd (II) by composite PU/HAp. Also comparative analysis of adsorption of Cd and Ni by composite PU/HAp were conducted, as well as comparative tests of adsorption of Cd (coconut fibre) and Ni (sisal fibre). It was possible to verify that the composite PU/HAp 40% showed better effectiveness for the removal of Cd (II) and Ni (II), above 80%, equivalent to the lignocellulosic fibre used and HAp produced. As main conclusion, it can be referred that the composite PU/HAp 40% is an effective adsorvent to wastewater treatment for heavy metal removal, with low cost and high efficiency

Estudo da introdução de resíduo de britagem de rocha calcária e cinza de biomassa de cana-de-açúcar em formulações de argamassas colantes

The adhesive mortars are a mixture of cement, sand, and additives to polymers that retain the mixing water and promotes adherence, being used in setting on various ceramic substrates. The sand used in the production of these mortars is from the riverbeds, and with the increasing restriction of these sands extraction by environmental agencies, and often having to be transported over long distances to the consumer center. This work aims to design and physical and mechanical characterization of ecological adhesive mortar with total replacement of natural sand by sand from the crushing of limestone, and the addition of mineral ash biomass of cane sugar in partial replacement cement used in the production of adhesive mortar , aiming compositions that meet the regulatory specifications for use adhesive mortar. Standardized tests to determine the tensile bond strength (NBR 14081-4), determination of open time (NBR 14081-3) and determination of slip (NBR 14081-5) were performed. Were also conducted trials squeeze flow in different formulation, the mortar with addition of 15 % gray biomass of cane sugar for cement mortars as well as the total replacement of natural sand by sand limestone crushing, got the best performance among the mortars studied, it was found that the addition of biomass to replace cement is perfectly feasible due to its pozzolanic activity, which contributed to this reduction in the cement matrix formation of adhesive mortar

Competitividade de diferentes atmosferas de plasma sobre as propriedades hidrofílicas em tecidos de polilático

Os polímeros biodegradáveis, como o poliácido láctico (PLA) apesar de consolidado nos campos farmacêuticos, médico e biomédico como biomateriais úteis para aplicações variadas, porém, depende da necessidade de funcionalizar a sua superfície estudando suas propriedades tais como hidrofilidade e hidrofobicidade favorecendo a interação do polímero com os materiais de aplicação farmacêutica, médica e biomédica. Este trabalho tem como objetivo produzir um material com características diferentes em cada um de seus lados, sendo um lado hidrofílico e o outro hidrofóbico. O substrato têxtil utilizado neste estudo foi um tecido de malha de composição 100% PLA que é biodegradável e biocompatível, o que possibilita sua aplicação na área biomédica. Para modificação superficial foi utilizado o tratamento a plasma de baixa pressão. A técnica de modificação de superfície por plasma foi escolhida por ser uma tecnologia limpa, anticorrosiva e não tóxica ao contrario de muitos processos químicos convencionais utilizados na indústria têxtil, além disso, não afeta as propriedades de massa do substrato. Neste estudo, um lado da superfície do substrato foi tratado com plasma oxigênio, argônio e nitrogênio, para o trabalho de melhoria da hidrofilidade da superfície e metano para a hidrofobicidade da amostra. A espectroscopia de emissão ótica (OEE) foi utilizada para fazer o diagnóstico das espécies do plasma durante o tratamento. Após o tratamento a plasma as amostras foram caracterizadas por medidas de ângulo de contato, microscopia eletrônica de varredura (MEV), Espectroscopia de fotoelétrons de raios-X (XPS), Infravermelho com Transformada de Fourier (FTIR) de reflexão total atenuada (ATR), medidas da área de espalhamento do líquido e arraste vertical. Onde foi caracterizado o aumento e diminuição da molhabilidade das amostras tratadas por plasma bem como as variáveis que contribuíram para tal efeito. O tratamento das amostras de PLA com O2 + CH4 apresenta comportamento hidrofílico no lado tratado com O2, apresentando aumento de rugosidade e grupos funcionais e no lado tratado com CH4, apresentando a formação de um filme polimérico formado sobre a superfície da amostra. O tratamento com N2 + CH4 apresenta comportamento hidrofóbico, porém com variações no fluxo do CH4 tem-se um controle da molhabilidade na superfície das amostras, podendo ir de hidrofóbico a hidrofílico, neste tratamento as amostras apresentaram pequenas diferenças de molhabilidade entre os lados tratados com plasma de N2 e com plasma de CH4

Avaliação e modelagem reológica de fluido de perfuração base água

The determination of the rheology of drilling fluids is of fundamental importance to select the best composition and the best treatment to be applied in these fluids. This work presents a study of the rheological behavior of some addictives used as viscosifiers in water-based drilling fluids. The evaluated addictives were: Carboxymethylcellulose (CMC), Xanthan gum (GX), and Bentonite. The main objective was to rheologically characterize suspensions composed by these addictives, by applying mathematical models for fluid flow behavior, in order to determine the best flow equation to represent the system, as well as the model parameters. The mathematical models applied in this research were: the Bingham Model, the Ostwald de Wale Model, and the Herschel-Bulkley Model. A previous study of hydration time for each used addictive was accomplished seeking to evaluate the effect of polymer and clay hydration on rheological behavior of the fluid. The rheological characterization was made through typical rheology experiments, using a coaxial cylinder viscosimeter, where the flow curves and the thixotropic magnitude of each fluid was obtained. For each used addictive the rheological behavior as a function of temperature was also evaluated as well as fluid stability as a function of the concentration and kind of addictive used. After analyses of results, mixtures of polymer and clay were made seeking to evaluate the rheological modifications provided by the polymer incorporation in the water + bentonite system. The obtained results showed that the Ostwald de Waale model provided the best fit for fluids prepared using CMC and for fluids with Xanthan gum and Bentonite the best fit was given by the Herschel-Bulkley one

Nano emulsões aplicadas a recuperação avançada de petróleo

A exploração de petróleo está a cada dia em circunstâncias mais adversas, no que diz respeito à profundidade dos poços como também, em relação à fluidez do óleo. Os reservatórios de descobertas recentes não possuem energia própria para produzir ou os métodos convencionais não são eficientes para fazer com que esses reservatórios tenham uma vida útil elevada, devido a alterações das propriedades físico-químicas, como por exemplo a viscosidade, que torna o deslocamento do óleo pelos poros do reservatório até a superfície cada vez mais complexo. O presente trabalho tem como objetivo estudar a preparação, caracterização e a utilização de nanoemulsões obtidas a partir de sistemas microemulsionados, com e sem a presença de polímero. Esses sistemas foram aplicados como método químico de recuperação de petróleo, com o intuito de obter maior eficiência de volume de óleo deslocado. O interesse por esse tipo de sistema existe devido a sua baixa tensão superficial, o pequeno tamanho de gotícula e, principalmente, pelo baixo percentual de matéria ativa presente em sua composição. Os ensaios realizados para caracterizar esses sistemas foram: aspecto físico, medidas de tamanho de gotícula, índice de polidispersão, tensão superficial, pH e condutividade. Ensaios de reologia e de adsorção dos sistemas foram realizados com o objetivo de avaliar sua influencia na recuperação de petróleo. Os ensaios de recuperação foram realizados em um equipamento que simula as condições de um reservatório de petróleo, utilizando plugs de rocha arenito Botucatu. Esses plugs foram saturados com salmoura (KCl 2%) e com petróleo proveniente da Bacia Potiguar do campo de Ubarana. Após essas etapas foi realizada a recuperação convencional utilizando a salmoura e, por último, foi injetada, a nanoemulsão, como método de recuperação avançada. Os sistemas obtidos variaram de 0% à 0,4% de polímero. Os ensaios de tamanhos de partícula obtiveram como resultado uma variação de 9,22 a 14,8 nm, caracterizando que as nanoemulsões estão dentro da faixa de tamanho inerente a esse tipo de sistema. Para ensaios de tensão superficial os valores foram na faixa de 33,6 a 39,7 dynas/cm, valores semelhantes à microemulsões e bem abaixo da tensão superficial da água. Os resultados obtidos para os valores de pH e condutividade se mantiveram estáveis ao longo do tempo de armazenamento, essa avaliação indica estabilidade das nanoemulsões estudadas. O teste de recuperação avançada utilizando nanoemulsão com baixo percentual de matéria ativa obteve como resultado de eficiência de deslocamento 39,4%. Porém esse valor foi crescente, de acordo com o aumento do percentual de polímero na nanomeulsão. Os resultados de eficiência de deslocamento de petróleo estão diretamente relacionados com o aumento da viscosidade das nanoemulsões. A nanoemulsão V (0,4% polímero) é o sistema mais viscoso dentre os analisados, e obteve o maior percentual de óleo deslocado (76,7%), resultando na maior eficiência de deslocamento total (90%). Esse estudo mostrou o potencial de sistemas nanoemulsionados, com e sem polímeros, na recuperação avançada de petróleo. Eles apresentam algumas vantagens com relação a outros métodos de recuperação avançada, como: o baixo percentual de matéria ativa, baixo índice de adsorção do polímero, dissolvido em nanoemulsão, na rocha e alta eficiência de recuperação

Degradação fotoquímica de efluentes industriais contendo polipropileno e isoniazida

One of the main impacts to the environment is the water pollution, where the industrial sector is one of the main sources of this problem. In order to search for a solution, the industrial sector is looking forward to new technologies to treat its wastewaters with the goal to reuse the water in the own process. In this mode, the treatment presents a reduction in its costs with the water suply. One of these technologies that are getting more and more applications is the advanced oxidative processes (AOP´s). In this work two industrial wastewaters have been studied, i.e., containing polymers and pharmacus. In the case of the wastewaters with polymers the UV/H2O2 process has been applied with a systematic series of experiments, using irradiation from a mercury lamp and also solar. The following variables of the UV/H2O2 process for the polymers wastewaters have been studied systematically with the lamp reactor: mode of addition of hydrogen peroxide, temperature, time of reaction, hydrogen peroxide concentration and power of the lamp (80, 125, 250 and 400W). The results demonstrated to be satisfactory, obtaining rates of organic charge removal of 100% in 120 minutes of reaction. The studied variables for the experiments with solar irradiation using polymers wastewaters were only the time of reaction, the mode of addition and concentration of the hydrogen peroxide. The results with the solar irradiation demonstrated to be not satisfactory, reaching maximum of 22% of TOC removal in 240 minutes of reaction. This is in accordance with the fact that the solar source has only 5% of low UV irradiation. With respect to the photodegradation of the pharmacus wastewaters, the process UV/H2O2 and photo-Fenton have been applied. As a source of photons, in this case, a mercury UV lamp of 80 W has been used. The studied variables for the experiments with artificial irradiation with the pharmacus wastewaters were: initial concentration of the pollutant, concentration of Fe2+ and time of reaction. The results demonstrated a degree of degradation fairly satisfactory, showing a maximum conversion value of 46% in 120 minutes

Preparação de poliuretana à base de óleo de mamona

Polyurethanes are very versatile macromolecular materials that can be used in the form of powders, adhesives and elastomers. As a consequence, they constitute important subject for research as well as outstanding materials used in several manufacturing processes. In addition to the search for new polyurethanes, the kinetics control during its preparation is a very important topic, mainly if the polyurethane is obtained via bulk polymerization. The work in thesis was directed towards this subject, particularly the synthesis of polyurethanes based castor oil and isophorone diisocianate. As a first step castor oil characterized using the following analytical methods: iodine index, saponification index, refraction index, humidity content and infrared absorption spectroscopy (FTIR). As a second step, test specimens of these polyurethanes were obtained via bulk polymerization and were submitted to swelling experiments with different solvents. From these experiments, the Hildebrand parameter was determined for this material. Finally, bulk polymerization was carried out in a differential scanning calorimetry (DSC) equipment, using different heating rates, at two conditions: without catalyst and with dibutyltin dilaurate (DBTDL) as catalyst. The DSC curves were adjusted to a kinetic model, using the isoconversional method, indicating the autocatalytic effect characteristic of this class of polymerization reaction

Não-extensividade em percolação por ligações de longo - alcance

A linear chain do not present phase transition at any finite temperature in a one dimensional system considering only first neighbors interaction. An example is the Ising ferromagnet in which his critical temperature lies at zero degree. Analogously, in percolation like disordered geometrical systems, the critical point is given by the critical probability equals to one. However, this situation can be drastically changed if we consider long-range bonds, replacing the probability distribution by a function like . In this kind of distribution the limit α → ∞ corresponds to the usual first neighbor bond case. In the other hand α = 0 corresponds to the well know "molecular field" situation. In this thesis we studied the behavior of Pc as a function of a to the bond percolation specially in d = 1. Our goal was to check a conjecture proposed by Tsallis in the context of his Generalized Statistics (a generalization to the Boltzmann-Gibbs statistics). By this conjecture, the scaling laws that depend with the size of the system N, vary in fact with the quantitie

Alquilação redutiva da quitosana a partir do glutaraldeído e 3-amino-1-pr

Chitosan derivatives were prepared by reductive alkylation using glutaraldehyde and 3-amino-1-propanol. The reducing agent used was the sodium borohydride. Tests of solubility, stability and viscosity were performed in order to evaluate these parameters effects in the reaction conditions (molar ratio of the reactants and presence of nitrogen in the reaction system). The molecular structure of commercial chitosan was determined by infrared (IR) and hydrogen nuclear magnetic resonance spectroscopy (1H NMR). The intrinsic viscosity and average molecular weight of the chitosan were determined by viscosimetry in 0.3 M acetic acid aqueous solution 0.2 M sodium acetate at 25 ºC. The derivatives of chitosan soluble in aqueous acidic medium were characterized by 1H NMR. The rheological behavior of the chitosan and of the derivative of chitosan (sample QV), which presented the largest viscosity, were studied as a function of polymer concentration, temperature and ionic strength of the medium. The results of characterization of the commercial chitosan (the degree of deacetylation obtained equal 78.45 %) used in this work confirmed a sample of low molar weight (Mv = 3.57 x 104 g/mol) and low viscosity (intrinsic viscosity = 213.56 mL/g). The chemical modification of the chitosan resulted in derivatives with thickening action. The spectra of 1H NMR of the soluble derivatives in acid aqueous medium suggested the presence of hydrophobic groups grafted into chitosan in function of the chemical modification. The solubility of the derivatives of chitosan in 0.25 M acetic acid aqueous solution decreased with increase of the molar ratio of the glutaraldehyde and 3-amino-1-propanol in relation to the chitosan. The presence of nitrogen and larger amount of reducing agent in reaction system contributed to the increase of the solubility, the stability and the viscosity of the systems. The viscosity of the polymeric suspensions in function of the shear rate increased significantly with polymer concentration, suggesting the formation of strong intermolecular associations. The chitosan presented pseudoplastic behavior with the increase in polymer concentration at a low shear rate. The derivative QV presented pseudoplastic behavior at all concentrations used and in a large range of shear rate. The viscosity of chitosan in solution decreased with an increase of the temperature and with the presence of salt. However, there was an increase of the viscosity of the chitosan solution at higher temperature (65 ºC) and ionic strength of the medium which were promoted by hydrophobic associating of the acetamide groups. The solutions of the chitosan derivatives (sample QV) were significantly more viscous than chitosan solution and showed higher thermal stability in the presence of salt as a function of the hydrophobic groups grafted into chitosan backbone

Hidrólise e caracterização de poliacrilamida hidrofobicamente modificada: avaliação da aplicabilidade na recuperação de petróleo

The hydrolysis reaction in alkaline conditions of the commercial polymer poly(acrylamide-co-metacrylate of 3,5,5-trimethyl-hexane) called HAPAM, containing 0.75 % of hydrophobic groups, was carried out in 0.1 M NaCl and 0.25M NaOH solutions, varying the temperature and reaction time. The polymers were characterized by 1H and 13C Nuclear Magnetic Resonance (NMR), Elemental Analysis and Size Exclusion Chromatography (SEC). The values of the hydrolysis degree were obtained by 13C NMR. The viscosity of HAPAM and HAPAM-10N-R solutions was evaluated as a function of shear rate, ionic strength and temperature. At high polymer concentration (Cp), the viscosity of HAPAM solutions increased with the ionic strength and decreased with the temperature. The viscosity of HAPAM-10N-R solutions increased significantly in distilled water, due to repulsions between the carboxylate groups. At high Cp, with the increase of ionic strength and temperature, occurred a decrease of viscosity, due to mainly the high hydrolysis degree and the low amount of hydrophobic groups. These results indicated that the studied polymers have properties more suitable for the application in Enhanced Oil Recovery (EOR) in low salinity and moderate temperature reservoirs

Obtenção e Caracterização Físico-Química do Sistema Compósito PEG-TiO2

Hybrid systems formed from polymers and transition metals have now their physical and chemical properties extensively investigated for use in electronic devices. In this work, Titanium Dioxide (TiO2) from the precursor of titanium tetrabutoxide and the composite system Poly(Ethylene Glycol)-Titanium Dioxide (TiO2-PEG) were synthesized by sol-gel method. The PEG as acquired and TiO2 and composites powders were analyzed by X-Ray Diffraction (XRD), Spectroscopy in the Infrared region with Fourier transform (IRFT), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS). In the XRD analysis were observed in the TiO2 crystal faces of one of its polymorphs - anatase phase, crystal planes in Poly (Ethylene Glycol) with considerable intensity and in the composite systems the mixture of crystal faces of their precursors isolated and reduction of crystallinity. The TG / DTG suggested increasing the thermal instability of PEG in the composite powders as TiO2 is incorporated into the system. Spectral analysis presented in the infrared overlapping bands for the polymer and metal oxide, reducing the intensity of symmetric stretching of ligand groups in the main chain polymer and angular deformations; were observed using SEM micrographs of the morphological changes suffered by composite systems with the variation of the oxide concentration. Analyses by impedance spectroscopy indicated that the increased conductivity in composite occurs in line with the addition of the metal oxide concentration in the composite system