Thermal characterization and rheological behavior of some varnishes and paints used for wood protection
International Journal of Environmental Science and Technology, 2021
They were analyzed the thermal and rheological behavior of several varnishes and paints, used for... more They were analyzed the thermal and rheological behavior of several varnishes and paints, used for wood protection, available on the market. The thermogravimetric analysis coupled with mass spectrometry and Fourier transform infrared spectrometry technique revealed that the degradation mechanism is complex and includes two to five decomposition stages depending on the composition. The analysis of the gases resulting from the decomposition processes of the water-based samples showed that carbon dioxide was the main potentially harmful product, whereas for those containing solvent these harmful agents were as follows: benzene, xylene and carbon dioxide. The decomposition of the sample containing urea-alkyd resins also results in hydrocyanic acid. The rheological tests showed a viscoelastic solid behavior in the case of water-based film-forming products, and a viscoelastic liquid behavior in the case of solvent-based ones. The microscale combustion calorimetry technique confirmed that this sample has the lowest thermal stability and can contribute the most to the triggering of fires.
Journal of Analytical and Applied Pyrolysis, Mar 1, 2016
This study assesses the thermal and thermo-oxidative stability and establishes the degradation me... more This study assesses the thermal and thermo-oxidative stability and establishes the degradation mechanism for five aromatic polyetherimides, by simultaneous mass spectrometry and Fourier transform infrared spectroscopy of off-gases from thermogravimetric analyzer in two working atmospheres: air and helium. Aromatic polyetherimides were synthesized starting from 4,4-(4,4isopropylidenediphenoxy)bis(phthalic anhydride) and five aromatic diamines, three of them containing 1,3,4-oxadiazole ring. The study establishes the influence of the structure and of the working atmosphere on the thermal stability and the start mechanism of thermal degradation. Moreover, it determines the main decomposition products both in inert atmosphere (helium) and in air.
This paper presents a thermogravimetric study of azo-polysiloxanic materials that may be used as ... more This paper presents a thermogravimetric study of azo-polysiloxanic materials that may be used as supports for cells culture. This type of polymer may generate nanostructured surfaces when subjected to laser irradiation, yielding a cell response that depends on surface relief. Modification of cell growth supports using nanostructured synthetic materials improves general understanding of the complex mechanisms that control cell adhesion and migration in normal conditions, as well as in various pathologies. These polymers require good thermal stability, since they need to be able to withstand both the interaction with the laser source, as well as various sterilization processes, without noticeable alteration in structure and properties. Thermal stability analysis confirms that the azo-polysiloxanic materials under study here may be used up to 300 °C in dynamic temperature conditions and also for a period of 40 minutes in isothermal conditions at 180 °C.
Thermal behavior, decomposition mechanism by TG/MS/FTIR technique and theoretical study of some symmetric and asymmetric bent-core liquid crystals based on 2,7-dihydroxynaphthalene
Journal of Thermal Analysis and Calorimetry, Jun 2, 2022
Despite a recent sustained preoccupation for developing biobased epoxies with enhanced applicabil... more Despite a recent sustained preoccupation for developing biobased epoxies with enhanced applicability, such products have not been widely accepted for industry because of their inferior characteristics compared to classic petroleum-based epoxy thermosets. Therefore, significant effort is being made to improve the flame retardance of the most commonly used epoxies, such as diglycidyl ether-based bisphenol A (DGEBA), bisphenol F (DGEBF), novalac epoxy, and others, while continuously avoiding the use of hazardous halogen-containing flame retardants. Herein, a phosphorus-containing bisphenol, bis(4-(((4-hydroxyphenyl)amino)(6-oxido-6H-dibenzo[c,e][1,2]oxaphosphinin-6-yl)methyl)phenyl) phenylphosphonate (BPH), was synthesized by reacting bis(4-formylphenyl)phenylphosphonate with 4-hydroxybenzaldehyde followed by the addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to the resulting azomethine groups. Environmentally friendly epoxy-based polymer thermosets were prepared...
The progress of digital technologies demands more speed and larger storage capacity. Optical stor... more The progress of digital technologies demands more speed and larger storage capacity. Optical storage systems have the advantage of being cheap, fast and capacious. This article explores the potential use of polyimide-based films as a recording medium for optical storage devices. The materials were designed through a host–guest approach that involves a cyano-containing polyimide precursor and an azochromophore combined in the following ratios: 1:0.25, 1:0.5, 1:0.75 and 1:1. After thermal treatment up to 200 °C, polyimide systems were formed with supramolecular structures constructed via hydrogen bonding as shown by molecular modeling and FTIR at around 3350 cm−1. The aspects arising from the variation of the azo-dye content in the polyimide samples and their impact on the vitrification temperature, colorimetric features, refractive index, band gap, non-linear optical susceptibility and birefringence were investigated for the first time. The thermal analysis indicated a slight decreas...
The progress of the automated industry has introduced many benefits in our daily life, but it als... more The progress of the automated industry has introduced many benefits in our daily life, but it also produces undesired electromagnetic interference (EMI) that distresses the end-users and functionality of electronic devices. This article develops new composites based on a polyetherimide (PEI) matrix and cobalt ferrite (CoFe2O4) nanofiller (10–50 wt%) by mixing inorganic phase in the poly(amic acid) solution, followed by film casting and controlled heating, to acquire the corresponding imide structure. The composites were designed to contain both electric and magnetic dipole sources by including highly polarizable groups (phenyls, ethers, -CN) in the PEI structure and by loading this matrix with magnetic nanoparticles, respectively. The films exhibited high thermal stability, having the temperature at which decomposition begins in the interval of 450–487 °C. Magnetic analyses indicated a saturation magnetization, coercitive force, and magnetic remanence of 27.9 emu g−1, 705 Oe, and 9....
Among the multitude of polymers with carbon-based macromolecular architectures that easily ignite... more Among the multitude of polymers with carbon-based macromolecular architectures that easily ignite in certain applications where short circuits may occur, polyimide has evolved as a class of polymers with high thermal stability while exhibiting intrinsic flame retardancy at elevated temperatures via a char-forming mechanism. However, high amounts of aromatic rings in the macromolecular backbone are required for these results, which may affect other properties such as film-forming capacity or mechanical properties; thus, much work has been done to structurally derivatize or make hybrid polyimide systems. In this respect, flexible polyimide films (PI(1–4)) containing bulky 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) units have been developed starting from commercial dianhydrides and an aromatic diamine containing two side chain bulky DOPO groups. The chemical structure of PI(1–4)) was characterized by 1H NMR, 13C NMR and 31P NMR spectroscopy. The optical properties, inclu...
Due to the pressing problems of today’s world, regarding both the finding of new, environmentally... more Due to the pressing problems of today’s world, regarding both the finding of new, environmentally friendly materials which have the potential to replace classic ones, and the need to limit the accelerated spread of bacteria in hospitals, offices and other types of spaces, many researchers have chosen to develop their work in this field. Thus, biopolymeric materials have evolved so much that they are gradually becoming able to remove fossil-based plastics from major industries, which are harmful to the environment and implicitly to human health. The biopolymer employed in the present study, Arboblend V2 Nature with silver nanoparticle content (AgNP) meets both aspects mentioned above. The main purpose of the paper is to replace several parts and products in operation which exhibit antibacterial action, preventing the colonization and proliferation of bacteria (Streptococcus pyogenes and Staphylococcus aureus, by using the submerged cultivation method), but also the possibility of deg...
Environmental Engineering and Management Journal, 2021
The aim of this study is to gain a better understanding of ash properties that makes it suitable ... more The aim of this study is to gain a better understanding of ash properties that makes it suitable for obtaining geopolymeric/zeolitic materials, as well as to demonstrate that thermal analysis can be used as an innovative procedure to compare different activation methods. Establishing a relationship between the physical and chemical characteristics of ash and materials obtained from fly ash is an important step towards producing large quantities of zeolitic materials with pre-established properties. In this paper, a direct relationship between TG analysis and the type of materials obtained from the local fly ash, by different methods, was proved for the first time. The experimental results demonstrated that the materials with a surface area over 40 m 2 /g and pores volume over 0.12 cm 3 /g exhibited the highest thermal loss. The samples exhibiting thermal loss over 10% contained zeolites phases, a fact confirmed by FT-IR and XRD, and more than 7% sodium in samples structure, as demonstrated by EDAX analysis. The results shown that thermal analysis allowed identification of the materials, as well as elucidation of the processes occurring during the thermal heating. Concordant to this study, the conditions for the optimum activation method consisted in: direct activation method, temperature equal to 363 o K, contact time 4 h, 1/3 solid/liquid ratio and use of 5M NaOH activation solution. It is known that TG/DTG analysis is an easy and the economic feasible method. TG analysis for establishing the zeolitization degree on the base of the number of stages (four stages), but more important, on the base of total mass losses (over 10%) is recommended.
Hemp fibres used as a reinforcing agent and three polymeric matrices (polypropylene, bicomponent,... more Hemp fibres used as a reinforcing agent and three polymeric matrices (polypropylene, bicomponent, recycled polyester) were used to obtain composite materials by needle punching and heat pressing. The influence of the hemp/matrix ratio and the nature of the matrix on the properties of the composites were analysed. The obtained composites were characterised by physical–mechanical indices, thermal analysis (thermogravimetry (TG), differential thermogravimetry (DTG) and Differential Scanning Calorimetry (DSC)), Fourier Transform Infrared Spectroscopy (FTIR-ATR) analysis, Scanning Electron Microscopy (SEM) and Chromatic measurements. The mechanical properties of composites are influenced by both the hemp/matrix ratio and the nature of the matrix. The thermal stability of composites decreased as the amount of hemp increased (for the same mass losses, the decomposition temperature decreased significantly for composites containing a quantity of hemp greater than 50%). Regarding the nature o...
Bent-core (BC) molecules became an attractive liquid crystal class due to their potential use in ... more Bent-core (BC) molecules became an attractive liquid crystal class due to their potential use in smart displays and photonic devices. In contrast to calamitic mesogens, bent-shaped mesogens are self-organized superstructures with remarkable properties, given the presence of polar order in mesophases, although the molecules themselves are not chiral. A particular interest represents the biaxial nematic liquid crystal materials that are used in display technology and allow a faster switching response, compared to calamitic liquid crystals, with considerably reduced costs. This chapter briefly reviews the bent-core liquid crystals with three different core units in the structure: (1) 2,5-disubstituted oxadiazole, (2) 1,3disubstituted benzene, and (3) 2,7-disubstituted naphthalene. To the central bent units (BUs) containing reactive functional groups of phenolic or aminic type, various mesogenic groups are symmetrically or asymmetrically connected, via esterification or condensation reactions. The obtained compounds showed biaxial nematic and/or smectic mesophases with high transition temperatures in the case of oxadiazole derivatives or cholesteric and banana-type mesophases with lower transition temperatures in the case of benzene and naphthalene derivatives.
Designing and self-assembly of unconventional star-shaped mesogens or 'hekates' are of interest t... more Designing and self-assembly of unconventional star-shaped mesogens or 'hekates' are of interest to materials science and molecular electronics. This work presents the synthesis of several symmetric trimeric liquid crystalline compounds comprising 1,3,5-trihydroxybenzene (phloroglucinol) as central core. The liquid crystalline behaviour was induced by attaching three rod-like azo-aromatic semiflexible units to the central core via esteric linkages. Based on differential scanning calorimetry and polarising optical microscopy, the mesophase stability mainly depends on the alkyl chain length. The compounds showed monotropic or enantiotropic behaviour, except the compound with nine atoms on the chain end which is non-mesomorphic. In addition to the synthesis and mesophase characterisation, the self-assembled structures and individual properties have been characterised by molecular simulations.
Ketoprofen a non-steroidal anti-inflammatory drug was intercalated into Mg-Al hydrotalcites lamel... more Ketoprofen a non-steroidal anti-inflammatory drug was intercalated into Mg-Al hydrotalcites lamella as an inorganic host by different methods. The intercalation compounds were examined by X-ray diffraction (XRD), FTIR spectroscopy, differential thermal analysis and thermo gravimetric analysis. The XRD patterns of the samples the diffraction peaks are typical to those of well crystallized solids with the hydrotalcite structure. The FTIR spectroscopy and thermogravimetric (DTG) analysis point out the presence of the organic compound in the network structure of the synthesized hydrotalcites.
Shells resulting from food processing and agricultural activities, such as hard shells of apricot... more Shells resulting from food processing and agricultural activities, such as hard shells of apricot, are considered as wastes and are generally used as fuel. However, this residue shows promise as lignocellulosic feedstock for biorefineries, for its conversion to liquid fuel or bio-products. This study is dedicated to the characterization and isolation of lignin, cellulose and hemicelluloses from apricot shells (AS). The chemical composition and thermal stability of AS after chemical treatment with solvents (ethanol-toluene), cellulose, hemicelluloses and lignin were analyzed by standard methods, i.e. Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Further, almost 50.2 wt% of a water-insoluble extract was obtained after the bleaching process, which showed the removal of lignin, and the final percentages for this extraction were 50.2 ± 0.34%, 26.5 ± 0.83%, 23.7 ± 0.29% and 35 ± 1% for holocellulose, cellulose, hemicelluloses and lignin, respectively. FTIR spectroscopy evidenced the structure of lignin, cellulose and hemicelluloses. Thermal analysis and the kinetic study suggested that cellulose had higher thermal stability than the other components, with the activation energy of 289.62 kJ/mol. Thus, our results indicated the high potential of AS to be used as an environmentally friendly material in a biorefinery, as well as in the modern polymer and chemical industries.
Environmental Engineering and Management Journal, 2012
The thermogravimetric study of some ferrocene derivatives with liquid crystalline properties was ... more The thermogravimetric study of some ferrocene derivatives with liquid crystalline properties was conducted on a Mettler Toledo TGA-SDTA851e derivatograph. The data were recorded in 20 ml/min outflow nitrogen and air, within the 25-900 °C temperature range and at heating rates of: 7, 10, 13, 16 and 19C/min. The curves were processed in order to detect the thermal and kinetic characteristics by means of STAR software, more precisely on the "Kinetics n th order" module from Mettler Toledo. The thermogravimetric and kinetic studies revealed that the S2 ferrocene derivative presents a better thermal stability than the S1 derivative, regardless of the working atmosphere. The shape of the curves of apparent activation energies variation with the conversion degree, determined by means of the ASTM-E1641 method, provided data about the degradation mechanism. The TG-MS-FTIR study conducted on the sample S1 revealed a higher ionic current intensity for the m/z=28 ionic fragment in the first stage, which means that thermal degradation begins in the-N=N-group and continues by splitting the aromatic rings, the other linkage groups and the cholesteryl ending groups. The TG-MS-FTIR study carried out on the sample S1 also revealed the highest amount of CO 2 in the gases resulting from thermal decomposition. Therefore, this suggests its harmful effects on the environment, which consist of greenhouse effect enhancement, should there occur fires or should household waste be disposed of by incineration, considering the applications that these materials may have in displays technology.
The aim of this work is to present briefly the preparation methodology of four emulsions (named M... more The aim of this work is to present briefly the preparation methodology of four emulsions (named M2, M3, M6, and M7) based on extracted mint oil (Mentha Piperita) and their physical-chemical properties and quality characteristics (pH, density, acidity index, peroxide index, diene and triene content, in-time stability, humidity and fatty matter content), in order to select the most recommendable emulsion to be used in textile field. This work also underlines that the most stable emulsion is M6 emulsion followed by M3 emulsion.
The removal of Co(II) ions from aqueous media was done using three types of biochars obtained fro... more The removal of Co(II) ions from aqueous media was done using three types of biochars obtained from algae waste biomass, mustard waste biomass, and soy waste biomass. The biochar samples were obtained by pyrolysis of waste biomass resulted from biofules production, at relative low temperature (600–650 °C), and this procedure can be considered a suitable alternative to reduce the volume of such waste. FTIR spectra recorded for each type of biochar reveal the presence of several functional groups that can be used as binding sites for Co(II) retention. The batch biosorption experiments were performed as a function of initial Co(II) ions concentration and contact time, at constant solution pH (5.0), sorbent dose (8.0 g/L), and room temperature (25 ± 1 °C). The sorption experiments showed that the Co(II) ions retention reaches the equilibrium in maximum 60 min, and the maximum sorption capacity follows the order: Mustard biochar (MBC—24.21 mg/g) < soy biochar (SBC—19.61 mg/g) < alga...
Three selected mushrooms growing in Romania, i.e. Armillaria mellea (Vahl.: Fr.) P.Kumm., Boletus... more Three selected mushrooms growing in Romania, i.e. Armillaria mellea (Vahl.: Fr.) P.Kumm., Boletus edulis Bull. and Cantharellus cibarius Fr., were analyzed in terms of metal (measured in fruiting bodies) and crude polysaccharide content. Inductively coupled plasma mass spectrometry (ICP-MS) technique was used to determine the metal contents, revealing the abundant presence of several microelements such as copper (varied from 15.8 mg/kg in A. mellea to 64.1 mg/kg in C. cibarius), iron (varied from 118 mg/kg in B. edulis to 221 mg/kg in A. mellea) and zinc (varied from 77.3 mg/kg in A. mellea to 188 mg/kg in C. cibarius). Selenium content varied from 0.2 mg/kg in C. cibarius to 4.18 mg/kg in B. edulis. The yield of the crude polysaccharides content in mushrooms varied from 3.6% in Boletus edulis, to almost 7% in Armillaria mellea and their characterization was employed by Nuclear Magnetic Resonance and Infra-Red Spectroscopy, Gel Permeation Chromatography and Thermogravimetric Analysis. The antioxidant activity of the detected polysaccharides was evaluated by means of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging and ferrous ion chelating assays. The best DPPH radical scavenging activity was found in the crude polysaccharides extracted from A. mellea (CE 50 = 222 ± 3 μg/ mL).
Thermal characterization and rheological behavior of some varnishes and paints used for wood protection
International Journal of Environmental Science and Technology, 2021
They were analyzed the thermal and rheological behavior of several varnishes and paints, used for... more They were analyzed the thermal and rheological behavior of several varnishes and paints, used for wood protection, available on the market. The thermogravimetric analysis coupled with mass spectrometry and Fourier transform infrared spectrometry technique revealed that the degradation mechanism is complex and includes two to five decomposition stages depending on the composition. The analysis of the gases resulting from the decomposition processes of the water-based samples showed that carbon dioxide was the main potentially harmful product, whereas for those containing solvent these harmful agents were as follows: benzene, xylene and carbon dioxide. The decomposition of the sample containing urea-alkyd resins also results in hydrocyanic acid. The rheological tests showed a viscoelastic solid behavior in the case of water-based film-forming products, and a viscoelastic liquid behavior in the case of solvent-based ones. The microscale combustion calorimetry technique confirmed that this sample has the lowest thermal stability and can contribute the most to the triggering of fires.
Journal of Analytical and Applied Pyrolysis, Mar 1, 2016
This study assesses the thermal and thermo-oxidative stability and establishes the degradation me... more This study assesses the thermal and thermo-oxidative stability and establishes the degradation mechanism for five aromatic polyetherimides, by simultaneous mass spectrometry and Fourier transform infrared spectroscopy of off-gases from thermogravimetric analyzer in two working atmospheres: air and helium. Aromatic polyetherimides were synthesized starting from 4,4-(4,4isopropylidenediphenoxy)bis(phthalic anhydride) and five aromatic diamines, three of them containing 1,3,4-oxadiazole ring. The study establishes the influence of the structure and of the working atmosphere on the thermal stability and the start mechanism of thermal degradation. Moreover, it determines the main decomposition products both in inert atmosphere (helium) and in air.
This paper presents a thermogravimetric study of azo-polysiloxanic materials that may be used as ... more This paper presents a thermogravimetric study of azo-polysiloxanic materials that may be used as supports for cells culture. This type of polymer may generate nanostructured surfaces when subjected to laser irradiation, yielding a cell response that depends on surface relief. Modification of cell growth supports using nanostructured synthetic materials improves general understanding of the complex mechanisms that control cell adhesion and migration in normal conditions, as well as in various pathologies. These polymers require good thermal stability, since they need to be able to withstand both the interaction with the laser source, as well as various sterilization processes, without noticeable alteration in structure and properties. Thermal stability analysis confirms that the azo-polysiloxanic materials under study here may be used up to 300 °C in dynamic temperature conditions and also for a period of 40 minutes in isothermal conditions at 180 °C.
Thermal behavior, decomposition mechanism by TG/MS/FTIR technique and theoretical study of some symmetric and asymmetric bent-core liquid crystals based on 2,7-dihydroxynaphthalene
Journal of Thermal Analysis and Calorimetry, Jun 2, 2022
Despite a recent sustained preoccupation for developing biobased epoxies with enhanced applicabil... more Despite a recent sustained preoccupation for developing biobased epoxies with enhanced applicability, such products have not been widely accepted for industry because of their inferior characteristics compared to classic petroleum-based epoxy thermosets. Therefore, significant effort is being made to improve the flame retardance of the most commonly used epoxies, such as diglycidyl ether-based bisphenol A (DGEBA), bisphenol F (DGEBF), novalac epoxy, and others, while continuously avoiding the use of hazardous halogen-containing flame retardants. Herein, a phosphorus-containing bisphenol, bis(4-(((4-hydroxyphenyl)amino)(6-oxido-6H-dibenzo[c,e][1,2]oxaphosphinin-6-yl)methyl)phenyl) phenylphosphonate (BPH), was synthesized by reacting bis(4-formylphenyl)phenylphosphonate with 4-hydroxybenzaldehyde followed by the addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to the resulting azomethine groups. Environmentally friendly epoxy-based polymer thermosets were prepared...
The progress of digital technologies demands more speed and larger storage capacity. Optical stor... more The progress of digital technologies demands more speed and larger storage capacity. Optical storage systems have the advantage of being cheap, fast and capacious. This article explores the potential use of polyimide-based films as a recording medium for optical storage devices. The materials were designed through a host–guest approach that involves a cyano-containing polyimide precursor and an azochromophore combined in the following ratios: 1:0.25, 1:0.5, 1:0.75 and 1:1. After thermal treatment up to 200 °C, polyimide systems were formed with supramolecular structures constructed via hydrogen bonding as shown by molecular modeling and FTIR at around 3350 cm−1. The aspects arising from the variation of the azo-dye content in the polyimide samples and their impact on the vitrification temperature, colorimetric features, refractive index, band gap, non-linear optical susceptibility and birefringence were investigated for the first time. The thermal analysis indicated a slight decreas...
The progress of the automated industry has introduced many benefits in our daily life, but it als... more The progress of the automated industry has introduced many benefits in our daily life, but it also produces undesired electromagnetic interference (EMI) that distresses the end-users and functionality of electronic devices. This article develops new composites based on a polyetherimide (PEI) matrix and cobalt ferrite (CoFe2O4) nanofiller (10–50 wt%) by mixing inorganic phase in the poly(amic acid) solution, followed by film casting and controlled heating, to acquire the corresponding imide structure. The composites were designed to contain both electric and magnetic dipole sources by including highly polarizable groups (phenyls, ethers, -CN) in the PEI structure and by loading this matrix with magnetic nanoparticles, respectively. The films exhibited high thermal stability, having the temperature at which decomposition begins in the interval of 450–487 °C. Magnetic analyses indicated a saturation magnetization, coercitive force, and magnetic remanence of 27.9 emu g−1, 705 Oe, and 9....
Among the multitude of polymers with carbon-based macromolecular architectures that easily ignite... more Among the multitude of polymers with carbon-based macromolecular architectures that easily ignite in certain applications where short circuits may occur, polyimide has evolved as a class of polymers with high thermal stability while exhibiting intrinsic flame retardancy at elevated temperatures via a char-forming mechanism. However, high amounts of aromatic rings in the macromolecular backbone are required for these results, which may affect other properties such as film-forming capacity or mechanical properties; thus, much work has been done to structurally derivatize or make hybrid polyimide systems. In this respect, flexible polyimide films (PI(1–4)) containing bulky 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) units have been developed starting from commercial dianhydrides and an aromatic diamine containing two side chain bulky DOPO groups. The chemical structure of PI(1–4)) was characterized by 1H NMR, 13C NMR and 31P NMR spectroscopy. The optical properties, inclu...
Due to the pressing problems of today’s world, regarding both the finding of new, environmentally... more Due to the pressing problems of today’s world, regarding both the finding of new, environmentally friendly materials which have the potential to replace classic ones, and the need to limit the accelerated spread of bacteria in hospitals, offices and other types of spaces, many researchers have chosen to develop their work in this field. Thus, biopolymeric materials have evolved so much that they are gradually becoming able to remove fossil-based plastics from major industries, which are harmful to the environment and implicitly to human health. The biopolymer employed in the present study, Arboblend V2 Nature with silver nanoparticle content (AgNP) meets both aspects mentioned above. The main purpose of the paper is to replace several parts and products in operation which exhibit antibacterial action, preventing the colonization and proliferation of bacteria (Streptococcus pyogenes and Staphylococcus aureus, by using the submerged cultivation method), but also the possibility of deg...
Environmental Engineering and Management Journal, 2021
The aim of this study is to gain a better understanding of ash properties that makes it suitable ... more The aim of this study is to gain a better understanding of ash properties that makes it suitable for obtaining geopolymeric/zeolitic materials, as well as to demonstrate that thermal analysis can be used as an innovative procedure to compare different activation methods. Establishing a relationship between the physical and chemical characteristics of ash and materials obtained from fly ash is an important step towards producing large quantities of zeolitic materials with pre-established properties. In this paper, a direct relationship between TG analysis and the type of materials obtained from the local fly ash, by different methods, was proved for the first time. The experimental results demonstrated that the materials with a surface area over 40 m 2 /g and pores volume over 0.12 cm 3 /g exhibited the highest thermal loss. The samples exhibiting thermal loss over 10% contained zeolites phases, a fact confirmed by FT-IR and XRD, and more than 7% sodium in samples structure, as demonstrated by EDAX analysis. The results shown that thermal analysis allowed identification of the materials, as well as elucidation of the processes occurring during the thermal heating. Concordant to this study, the conditions for the optimum activation method consisted in: direct activation method, temperature equal to 363 o K, contact time 4 h, 1/3 solid/liquid ratio and use of 5M NaOH activation solution. It is known that TG/DTG analysis is an easy and the economic feasible method. TG analysis for establishing the zeolitization degree on the base of the number of stages (four stages), but more important, on the base of total mass losses (over 10%) is recommended.
Hemp fibres used as a reinforcing agent and three polymeric matrices (polypropylene, bicomponent,... more Hemp fibres used as a reinforcing agent and three polymeric matrices (polypropylene, bicomponent, recycled polyester) were used to obtain composite materials by needle punching and heat pressing. The influence of the hemp/matrix ratio and the nature of the matrix on the properties of the composites were analysed. The obtained composites were characterised by physical–mechanical indices, thermal analysis (thermogravimetry (TG), differential thermogravimetry (DTG) and Differential Scanning Calorimetry (DSC)), Fourier Transform Infrared Spectroscopy (FTIR-ATR) analysis, Scanning Electron Microscopy (SEM) and Chromatic measurements. The mechanical properties of composites are influenced by both the hemp/matrix ratio and the nature of the matrix. The thermal stability of composites decreased as the amount of hemp increased (for the same mass losses, the decomposition temperature decreased significantly for composites containing a quantity of hemp greater than 50%). Regarding the nature o...
Bent-core (BC) molecules became an attractive liquid crystal class due to their potential use in ... more Bent-core (BC) molecules became an attractive liquid crystal class due to their potential use in smart displays and photonic devices. In contrast to calamitic mesogens, bent-shaped mesogens are self-organized superstructures with remarkable properties, given the presence of polar order in mesophases, although the molecules themselves are not chiral. A particular interest represents the biaxial nematic liquid crystal materials that are used in display technology and allow a faster switching response, compared to calamitic liquid crystals, with considerably reduced costs. This chapter briefly reviews the bent-core liquid crystals with three different core units in the structure: (1) 2,5-disubstituted oxadiazole, (2) 1,3disubstituted benzene, and (3) 2,7-disubstituted naphthalene. To the central bent units (BUs) containing reactive functional groups of phenolic or aminic type, various mesogenic groups are symmetrically or asymmetrically connected, via esterification or condensation reactions. The obtained compounds showed biaxial nematic and/or smectic mesophases with high transition temperatures in the case of oxadiazole derivatives or cholesteric and banana-type mesophases with lower transition temperatures in the case of benzene and naphthalene derivatives.
Designing and self-assembly of unconventional star-shaped mesogens or 'hekates' are of interest t... more Designing and self-assembly of unconventional star-shaped mesogens or 'hekates' are of interest to materials science and molecular electronics. This work presents the synthesis of several symmetric trimeric liquid crystalline compounds comprising 1,3,5-trihydroxybenzene (phloroglucinol) as central core. The liquid crystalline behaviour was induced by attaching three rod-like azo-aromatic semiflexible units to the central core via esteric linkages. Based on differential scanning calorimetry and polarising optical microscopy, the mesophase stability mainly depends on the alkyl chain length. The compounds showed monotropic or enantiotropic behaviour, except the compound with nine atoms on the chain end which is non-mesomorphic. In addition to the synthesis and mesophase characterisation, the self-assembled structures and individual properties have been characterised by molecular simulations.
Ketoprofen a non-steroidal anti-inflammatory drug was intercalated into Mg-Al hydrotalcites lamel... more Ketoprofen a non-steroidal anti-inflammatory drug was intercalated into Mg-Al hydrotalcites lamella as an inorganic host by different methods. The intercalation compounds were examined by X-ray diffraction (XRD), FTIR spectroscopy, differential thermal analysis and thermo gravimetric analysis. The XRD patterns of the samples the diffraction peaks are typical to those of well crystallized solids with the hydrotalcite structure. The FTIR spectroscopy and thermogravimetric (DTG) analysis point out the presence of the organic compound in the network structure of the synthesized hydrotalcites.
Shells resulting from food processing and agricultural activities, such as hard shells of apricot... more Shells resulting from food processing and agricultural activities, such as hard shells of apricot, are considered as wastes and are generally used as fuel. However, this residue shows promise as lignocellulosic feedstock for biorefineries, for its conversion to liquid fuel or bio-products. This study is dedicated to the characterization and isolation of lignin, cellulose and hemicelluloses from apricot shells (AS). The chemical composition and thermal stability of AS after chemical treatment with solvents (ethanol-toluene), cellulose, hemicelluloses and lignin were analyzed by standard methods, i.e. Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Further, almost 50.2 wt% of a water-insoluble extract was obtained after the bleaching process, which showed the removal of lignin, and the final percentages for this extraction were 50.2 ± 0.34%, 26.5 ± 0.83%, 23.7 ± 0.29% and 35 ± 1% for holocellulose, cellulose, hemicelluloses and lignin, respectively. FTIR spectroscopy evidenced the structure of lignin, cellulose and hemicelluloses. Thermal analysis and the kinetic study suggested that cellulose had higher thermal stability than the other components, with the activation energy of 289.62 kJ/mol. Thus, our results indicated the high potential of AS to be used as an environmentally friendly material in a biorefinery, as well as in the modern polymer and chemical industries.
Environmental Engineering and Management Journal, 2012
The thermogravimetric study of some ferrocene derivatives with liquid crystalline properties was ... more The thermogravimetric study of some ferrocene derivatives with liquid crystalline properties was conducted on a Mettler Toledo TGA-SDTA851e derivatograph. The data were recorded in 20 ml/min outflow nitrogen and air, within the 25-900 °C temperature range and at heating rates of: 7, 10, 13, 16 and 19C/min. The curves were processed in order to detect the thermal and kinetic characteristics by means of STAR software, more precisely on the "Kinetics n th order" module from Mettler Toledo. The thermogravimetric and kinetic studies revealed that the S2 ferrocene derivative presents a better thermal stability than the S1 derivative, regardless of the working atmosphere. The shape of the curves of apparent activation energies variation with the conversion degree, determined by means of the ASTM-E1641 method, provided data about the degradation mechanism. The TG-MS-FTIR study conducted on the sample S1 revealed a higher ionic current intensity for the m/z=28 ionic fragment in the first stage, which means that thermal degradation begins in the-N=N-group and continues by splitting the aromatic rings, the other linkage groups and the cholesteryl ending groups. The TG-MS-FTIR study carried out on the sample S1 also revealed the highest amount of CO 2 in the gases resulting from thermal decomposition. Therefore, this suggests its harmful effects on the environment, which consist of greenhouse effect enhancement, should there occur fires or should household waste be disposed of by incineration, considering the applications that these materials may have in displays technology.
The aim of this work is to present briefly the preparation methodology of four emulsions (named M... more The aim of this work is to present briefly the preparation methodology of four emulsions (named M2, M3, M6, and M7) based on extracted mint oil (Mentha Piperita) and their physical-chemical properties and quality characteristics (pH, density, acidity index, peroxide index, diene and triene content, in-time stability, humidity and fatty matter content), in order to select the most recommendable emulsion to be used in textile field. This work also underlines that the most stable emulsion is M6 emulsion followed by M3 emulsion.
The removal of Co(II) ions from aqueous media was done using three types of biochars obtained fro... more The removal of Co(II) ions from aqueous media was done using three types of biochars obtained from algae waste biomass, mustard waste biomass, and soy waste biomass. The biochar samples were obtained by pyrolysis of waste biomass resulted from biofules production, at relative low temperature (600–650 °C), and this procedure can be considered a suitable alternative to reduce the volume of such waste. FTIR spectra recorded for each type of biochar reveal the presence of several functional groups that can be used as binding sites for Co(II) retention. The batch biosorption experiments were performed as a function of initial Co(II) ions concentration and contact time, at constant solution pH (5.0), sorbent dose (8.0 g/L), and room temperature (25 ± 1 °C). The sorption experiments showed that the Co(II) ions retention reaches the equilibrium in maximum 60 min, and the maximum sorption capacity follows the order: Mustard biochar (MBC—24.21 mg/g) < soy biochar (SBC—19.61 mg/g) < alga...
Three selected mushrooms growing in Romania, i.e. Armillaria mellea (Vahl.: Fr.) P.Kumm., Boletus... more Three selected mushrooms growing in Romania, i.e. Armillaria mellea (Vahl.: Fr.) P.Kumm., Boletus edulis Bull. and Cantharellus cibarius Fr., were analyzed in terms of metal (measured in fruiting bodies) and crude polysaccharide content. Inductively coupled plasma mass spectrometry (ICP-MS) technique was used to determine the metal contents, revealing the abundant presence of several microelements such as copper (varied from 15.8 mg/kg in A. mellea to 64.1 mg/kg in C. cibarius), iron (varied from 118 mg/kg in B. edulis to 221 mg/kg in A. mellea) and zinc (varied from 77.3 mg/kg in A. mellea to 188 mg/kg in C. cibarius). Selenium content varied from 0.2 mg/kg in C. cibarius to 4.18 mg/kg in B. edulis. The yield of the crude polysaccharides content in mushrooms varied from 3.6% in Boletus edulis, to almost 7% in Armillaria mellea and their characterization was employed by Nuclear Magnetic Resonance and Infra-Red Spectroscopy, Gel Permeation Chromatography and Thermogravimetric Analysis. The antioxidant activity of the detected polysaccharides was evaluated by means of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging and ferrous ion chelating assays. The best DPPH radical scavenging activity was found in the crude polysaccharides extracted from A. mellea (CE 50 = 222 ± 3 μg/ mL).
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