Robust interface on ENR-50/TiO2 nanohybrid material based sol-gel technique: Insights into synthesis,characterization and applications in optical

In this work, the sol–gel technique was used to prepare a new organic–inorganic hybrid from Epoxidized Natural Rubber (ENR-50) and Titanium dioxide (TiO₂) by blending different content of titania precursors (10, 30, and 50 wt%) with an ENR-50 matrix. A wide range of analyses was conducted to understand the nature of this hybrid and also to evaluate its potential uses in applications required high refractive index such as micro optical and optoelectronic devices. Results indicated that the ring-opening reaction of epoxide groups in ENR-50 increased with the increase of titania content in the hybrid resulting a strong bonding between titania and ENR-50 through TiOC bond, which was observed in FTIR spectrum at 1027–1028 cm⁻¹. It is also observed a slight decrease in the intensity of the amorphous peak along with a new crystalline peak appeared at 2θ = 23 and 27° due to the crystalline nature of titania. The hybrids showed three thermal degradation steps in the range of temperature 76 to 769 °C due to the existence of the Ti moieties with the mixture of polymer chains, which in turn shifted the T_g at 24.3, 26.9 and 28.1 °C for the hybrid at 10, 30, and 50 wt% TiO₂ compared to the T_g of ENR-50 at −18.4 °C respectively. The morphology of the ENR-50 showed clear changes during of the synthesis of ENR-50/TiO₂ hybrids, these changes were proven by SEM, TEM, and AFM analyses. Uv–Vis results showed that the higher wavelength peak at 293 nm has shifted to 296, 298 and 300 nm for the hybrid at 10, 30, and 50 wt% TiO₂ respectively due to the strong interaction between titania precursors and ENR-50 matrix. Furthermore, the hybrids showed good optical transparency in the visible light range.     

Thermal behaviour of cephalexin in different mixtures

The thermoanalytical curves (TA), i.e. TG, DTG and DTA for pure cephalexin and its mixtures with talc, magnesium stearate, starch and microcrystalline cellulose, respectively, were drawn up in air and nitrogen at a heating rate of 10 °C min⁻¹. The thermal degradation was discussed on the basis of EGA data obtained for a heating rate of 20 °C min⁻¹. Until 250 °C, the TA curves are similar for all mixtures, up this some peculiarities depending on the additive appears. These certify that between the pure cephalosporin and the excipients do not exists any interaction until 250 °C. A kinetic analysis was performed using the TG/DTG data in air for the first step of cephalexin decomposition at four heating rates: 5, 7, 10 and 12 °C min⁻¹. The data processing strategy was based on a differential method (Friedman), an integral method (Flynn–Wall–Ozawa) and a nonparametric kinetic method (NPK). This last one allowed an intrinsic separation of the temperature, respective conversion dependence on the reaction rate and less speculative discussions on the kinetic model. All there methods had furnished very near values of the activation energy, this being an argument for a single thermooxidative degradation at the beginning (192–200 °C).     

Synthesis And Kinetic Analysis of Poly(2,2'-dymethoxy-4,4'-biphenylenevinylene. A novel conducting polymer

The title polymer was obtained electrochemically by the reduction of 4,4'-bis(dibromomethyl)-2,2'-dimethoxybiphenyl under very smooth conditions. The DSC and TG/DTG curves registered at four different heating rates showed that the polymer is stable in air up to 150°C, where smooth degradation starts. Above 300°C, decomposition is fast and exothermic (ΔH= –323 J g^–1) . The activation energy (116±4 kJ mol^–1 ) was determined by Ozawa's method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermooxidative stabilization of a MDI

Samples of flexible PU foam were prepared from a polyol (Elastoflex W 5516/115) and an isocyanate prepolymer (Iso 145/8), both commercial Elastogram products. For the thermooxidative stabilization, two phenolic compounds were used, separately or in mixture. These compounds were: 2,6-di-t-butyl-4-methyl-phenol (non-reactive) (AO-1), 3,5-di-t-butyl-4-hydroxy-benzyl alcohol (reactive, AO-2), used in total mass% of 0.3/1.5. The TG/DTG/DTA curves were drawn up in dynamic air, with a heating rate of 10 °C min⁻¹, until 500 °C. For the unstabilized sample a single thermodegradative TG step, with a maximum rate at 268–270 °C was observed, whereas for the stabilized samples, supplementary steps at higher temperature were observed. The changes in the TG/DTG/DTA parameters are not in a single relationship with the mass% of the stabilizator, due to the following: AO-1 is easily migrated out from PV, especially, at higher concentrations. AO-2 had positive effect at all studied concentrations. But the most remarkable effect is the synergetic effect of a 1:1 mixture of AO-1 and AO-2.     

Thermal analysis of vitamin PP Niacin and niacinamide

Vitamin PP includes two vitamers, niacin and niacinamide which are essential for energy production. Vitamins are sensitive and losses can occur during shelf life and heating processes. Thermal analysis can provide information about thermal behavior of each vitamer relating them with time and/or temperature exposure. The vitamers thermal behavior were studied by TG/DTG and DSC under air and nitrogen atmosphere and the results showed that niacin is more stable than the niacinamide and the decomposition happens by volatilization at 238 °C while niacinamide melts at 129 °C and volatilize at 254 °C when there is the total mass loss in the TG/DTG curves.     

A Structural Study of Epoxidized Natural Rubber (ENR-50) and Its Cyclic Dithiocarbonate Derivative Using NMR Spectroscopy Techniques

A structural study of epoxidized natural rubber (ENR-50) and its cyclic dithiocarbonate derivative was carried out using NMR spectroscopy techniques. The overlapping ¹H-NMR signals of ENR-50 at δ 1.56, 1.68-1.70, 2.06, 2.15-2.17 ppm were successfully assigned. In this work, the ¹³C-NMR chemical shift assignments of ENR-50 were consistent to the previously reported work. A cyclic dithiocarbonate derivative of ENR-50 was synthesized from the reaction of purified ENR-50 with carbon disulfide (CS₂), in the presence of 4-dimethylaminopyridine (DMAP) as catalyst at reflux temperature. The cyclic dithiocarbonate formation involved the epoxide ring opening of the ENR-50. This was followed by insertion of the C-S moiety of CS₂ at the oxygen attached to the quaternary carbon and methine carbon of epoxidized isoprene unit, respectively. The bands due to the C=S and C-O were clearly observed in the FTIR spectrum while the ¹H-NMR spectrum of the derivative revealed the peak attributed to the methylene protons had split. The ¹³C-NMR spectrum of the derivative further indicates two new carbon peaks arising from the >C=S and quaternary carbon of cyclic dithiocarbonate. All other ¹H- and ¹³C-NMR chemical shifts of the derivative remain unchanged with respect to the ENR-50.     

Intercalation of water and guest molecules within Ca<Superscript>2+</Superscript>–Montmorillonite

The high potential for intercalations by water and various guest molecules is induced by the exchangeable cation inside Ca²⁺–Montmorillonite gallery. XRD peak for Mon at 2θ = 6.04° (d ₀₀₁ = 1.462 nm) shows the structural effect on the clay gallery influenced by the intercalated water layers. Further increases in the gallery height are observed with the intercalation of octadecyl ammonium cations in OMON (d ₀₀₁ = 1.840 nm) and ENR-50 matrix chains in CENR-50 (d ₀₀₁ = 1.954 nm). DSC studies on the other hand reveal the thermal behaviors of intercalated molecules that are linked to the exchangeable cations. The endothermic of Ca²⁺–Montmorillonite (H _Mon = 356.3 J/g) in low temperature range (30–100 °C) indicates the removal of free water and hydrogen bonded water molecules, while the endothermic around 150 °C is related to the induced skeletal layer of water within Ca²⁺–Montmorillonite. The OMON endothermic (H _OMON = 47.0 J/g, T _m = 36.94 °C) tells that cation exchange had modified the water structures and content inside the renewed clay. The intercalation of ENR-50 chains into OMON gallery reveals two endothermic with the T _m1 and T _m2 are at 86.24 and 113.80 °C, respectively. These T _ms confirm that the alkyl chain segment on octadecyl ammonium cation occupy the OMON interlayer space.     

Thermal behavior of cashew gum by simultaneous TG/DTG/DSC-FT-IR and EDXRF

Cashew gum, an exudate polysaccharide from Anacardium occidentale L., was purified by alcohol precipitation. Thermal behavior of this polysaccharide was investigated by simultaneous TG/DTG/DSC-FT-IR analysis performed under nitrogen and air atmospheres and heating rate of 10 K min^?1. TG/DTG curves under oxidative atmosphere were similar to the curves under N₂ atmosphere until 340 °C, however, it was observed a profile difference due to the presence of two DTG peaks at 430 and 460 °C. DSC results showed endothermic and exothermic events corroborating with TG/DTG curves. The Simultaneous TG/DSC-FTIR analysis revealed that evolved gases from the decomposition of cashew gum sample were CO₂, CO, and groups: O–H, C–H, C=O, C–C, and C–O, in nitrogen and air atmospheres. Energy dispersive X-ray fluorescence analysis from the ash showed that the elements in larger amounts are CaO, MgO, and K₂O.     

Thermal characterization of hydrotalcite used in the transesterification of soybean oil

Hydrotalcite was synthesised by co-precipitation method, calcined and characterized by XRD, BET, IR and TG/DTA/DTG analyses and tested as solid base catalyst in the transesterification of soybean oil with methanol, achieving a methyl ester content of 99.5%. The thermal decomposition of hydrotalcite calcined occurred in four mass loss steps at 28, 105, 203 and 400 °C. The hydrotalcite was recovered and through a simple evaluation by TG/DTA/DTG techniques it was found that at 500 °C is the temperature, where the organic matter should be eliminated from the catalyst. This study shows the importance of thermal analysis in the evaluation of the recovery temperature of hydrotalcite.     

Thermal behavior of verapamil in pure and in solid dosage forms

Verapamil is a phenyl-alchil-amine type pharmaceutical largely used as a specific calcium antagonist. Knowledge of drug-excipient compatibility represents an important phase in development of different dosage forms. Hyphenated techniques are versatile for obtaining such necessary information’s. The TG/DTG/DTA curves were obtained in air at different heating rates and in nitrogen. The IR spectra of pure compound and its char at 400 °C (by U-ATR technique) and the IR identification of Evolved Gasses allowed some discussions on the thermally induced events. In the solid dosage forms verapamil was mixed with talc, magnesium stearate, starch, and cellulose, and the corresponding thermoanalytical curves were compared with that one of pure I. No physical or chemical interactions were observed till 250 °C. A kinetic analysis was performed for TG step of verapamil between 250 and 350 °C. The data at four heating rates (7, 10, 12, 15 °C min⁻¹) were processed on a strategy using at last three different kinetic methods. For these, the NPK method seems to be less speculative, allowing an objective determination of the kinetic parameters.     

Compatibility and decomposition kinetics studies of prednicarbate alone and associated with glyceryl stearate

In this work, TG/DTG and DSC techniques were used to the determination of thermal behavior of prednicarbate alone and associated with glyceryl stearate excipient (1:1 physical mixture). TG/DTG curves obtained for the binary mixture showed a reduction of approximately 37 °C to the thermal stability of drug ( T_{\textdm/\textdt = 0 \textDTG}^\textMax T_{{{\text{d}}m/{\text{d}}t = 0\,{\text{DTG}}}}^{\text{Max}} ). The disappearance of stretching band at 1280 cm⁻¹ (ν_as C–O, carbonate group) and the presence of streching band with less intensity at 1750 cm⁻¹ (ν_s C–O, ester group) in IR spectrum obtained to the binary mixture submitted at 220 °C, when compared with IR spectrum of drug submitted to the same temperature, confirmed the chemical interaction between these substances due to heating. Kinetics parameters of decomposition reaction of prednicarbate were obtained using isothermal (Arrhenius equation) and non-isothermal (Ozawa) methods. The reduction of approximately 45% of activation energy value (E _a) to the first step of thermal decomposition reaction of drug in the 1:1 (mass/mass) physical mixture was observed by both kinetics methods.     

Effect of the Maillard reaction on properties of casein and casein films

The use of biodegradable natural polymers has increased due to the over-solid packaging waste. In this study, a chemical modification of the casein molecule was performed by Maillard reaction, and the modified polymer was evaluated by polyacrylamide gel electrophoresis (PAGE), thermogravimetry/derivative thermogravimetry (TG/DTG), FT-IR, and ¹H-NMR spectroscopy. Subsequently, films based on the modified casein were obtained and characterized by mechanical analysis, water vapor transmission, and erosion behavior. The PAGE results suggested an increase of molecular mass of the modified polymer, and FT-IR spectroscopy data indicated inclusion of C–OH groups into this molecule. The TG/DTG curves of modified casein presented a different thermal decomposition profile compared to the individual compounds. Mechanical tests showed that the chemical modification of the casein molecules provided higher elongation rates (45.5%) to the films, suggesting higher plasticity, than the original molecules (13.4%). The modified casein films presented higher permeability (0.505 ± 0.006 μg/h mm³) than the original polymer (0.387 ± 0.006 μg/h mm³) films at 90% relative humidity (RH). In pH 1.2, modified casein films presented higher erosion rates (32.690 ± 0.692%) than casein films (19.910 ± 2.083%) after 8 h, suggesting an increased sensibility for erosion of the modified casein films in acid environment. In water (pH 7.0), the films erosion profiles were similar. Those findings indicate that the modification of molecule by Maillard reaction provided films more plastic, hydrophilic, and sensitive to erosion in acid environment, suggesting that a new polymer with changed properties was founded.     

Kinetic study of the polymeric binder burnout in green low temperature co-fired ceramic tapes

The binder decomposition and burnout process of a commercial low temperature co-fired ceramic (LTCC) tape and an alumina tape which is used as a sacrificial tape for the constrained sintering process of the LTCC-tape was investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG) up to 550 °C at different heating rates (from 1.5 to 10 K min⁻¹) in air. TG revealed a multistage degradation behaviour of the binder system for both tapes, but the temperature range of the different degradation stages varied. The activation energy of decomposition was determined by the Flynn–Wall isoconversional method and the Coats–Redfern method.     

Catalytic pyrolysis of Phragmites (reed): Investigation of its potential as a biomass feedstock

In this paper, thermogravimetry, TG, and pyrolysis are used for the thermochemical evaluation of the common reed (Pragmites australis) as a candidate biomass feedstock. The TG analysis indicated that the material loses 4% of its weight below 150 °C through dehydration. The main decomposition reaction occurs between 200 and 390 °C. The rate of weight loss, represented by the derivative thermogravimetric, DTG, signal indicated a multi-step reaction. Kinetic analysis helped in the resolution of the temperature ranges of the overlapping steps. The first step corresponds to the degradation of the hemi-cellulosic fraction and the second to the cellulosic fraction degradation. The TG and DTG signals of reed samples treated with increasing concentration of potassium carbonate (0.6–10 wt%) indicated a catalytic effect of the salt on reed decomposition. The temperature of maximum weight loss rate, DTGmax, exponentially decreased with increasing catalyst content, whilst the initial temperature of the decomposition decreased linearly. The pyrolysis studies were carried out in a Pyrex vertical reactor with sintered glass disc to hold the sample and to aid the fluidization with the nitrogen stream flowing upwards. The reactor was connected to a cyclone and condenser and a gas sampling device. Tar and char are collected and weighed. The gas chromatographic analysis of the evolved gases demonstrated the effect of pyrolysis temperature (400, 450, and 500 °C) on their composition. The temperature increase favors the yields of hydrocarbons, carbon monoxide and hydrogen at the expense of methanol and carbon dioxide. Similarly, reed samples treated with K2CO3 at 10 wt% were pyrolyzed and analyzed. Comparisons for the various parameters (yields, gas composition and carbon–hydrogen recovery) between the untreated and catalyzed reed conversion were also made.     

Evaluation of CO2 adsorption capacity of solid sorbents

The CO₂ adsorption capacity of the low-cost solid sorbents of waste tire char (TC) and chicken waste char (CW) was compared with commercial active carbon (AC) and 5 ? zeolite (ZA) using thermogravimetric analysis (TG), pressurized TG, and differential scanning calorimetry (DSC). The sorbents were degassed in a TG up to 150 °C to release all gases on the surface of the sample, then cooled down to the designed temperature for adsorption. TG results indicated that the CO₂ adsorption capacity of TC was higher than that of CW, but lower than those of AC and ZA. The maximum adsorption rate of TC at 50 °C was 0.61% min⁻¹, lower than that of AC, but higher than that of CW, 0.44% min⁻¹. The maximum adsorption rate of ZA at 50 °C was 3.1% min⁻¹. When the pressure was over 4 bar, the adsorption rate of ZA was lower than that of TC and AC. At 30 bar, the total CO₂ uptake of TC was 20 wt%, higher than that of CW and ZA but lower than that of AC. The temperature, nitrogen concentration, and water content also influenced the CO₂ adsorption capacity of sorbents to some extent. DSC results showed that adsorption was an exothermic process. The heat of CO₂ adsorption per mole of CO₂ of TC at 50 °C was 24 kJ mol⁻¹ while the ZA had the largest heat of adsorption at 38 kJ mol⁻¹. Comparing the characteristics of TC and CW, TC may be a promising sorbent for removal of CO₂.     

Thermogravimetric Analysis of Corn Cob Impregnated With Zinc Chloride for Preparation of Activated Carbon

The thermochemical decomposition of agricultural by-product corn cob impregnated with ZnCl₂, as a precursor material for producing the activated carbons, was investigated by thermogravimetric (TG) analysis at the heating rate of 5 and 10°C min^–1 under a controlled atmosphere of nitrogen (60 ml min^–1). The appearance of a peak in the differential thermogravimetric plot (DTG) in the temperature range of 400–600°C is significantly related to the extent of impregnation. The DTG curve of the sample impregnated with the optimal impregnation ratio of 175% (i.e., the ratio of ZnCl₂ mass of 87.5 g in the 200 cm³ of water to corn cobmass of 50 g), which yields an optimal BET surface area of the activated carbon and displays a DTG peak at about 500°C. This may be partially due to the intense chemical activation and results in the formation of a porous structure in the activated solid residue. This observation is also in close agreement with previous results at optimal pyrolysis temperatures of 500°C and with similar experimental conditions. In order to support the results in the TG-DTG analysis, the development of pore structure of the resulting activated carbons thus obtained by previous studies was also examined and explained using the scanning electron microscopy (SEM). This revised version was published online in August 2006 with corrections to the Cover Date.     

A potential pentaerythritol-based bio-lubricants from 10-undecylenic acid: Its physico-chemical assessment

In this study, renewable, non-toxic, sulphur free bio-lubricants are synthesized as alternative for fossil fuels. We utilized a bio-derived 10-undecylenic acid (UDA) and pentaerythritol (PE) as raw materials to synthesize bio-lubricants by two-step chemical processes like esterification and followed by epoxidation reactions. And achieved a UDA-PE epoxide yielded 73.4%. The formation of UDA-PE ester and UDA-PE epoxide was confirmed by spectral analysis such as NMR (¹H and ¹³C), FTIR and mass spectra, Physico-chemical and basic lubricant properties by standard American Society for Testing and Materials methods (ASTM). The results showed that the products of UDA-PE ester and UDA-PE epoxide had high viscosity index (262 and 200), good pour points (−29 °C to −15 °C), high flash points (296 °C and 301 °C) respectively and these met the ISO VG (International Organization for Standardization-Viscosity grade) 22 and 220 standard values. In general, both synthesized products are plausible to be employed as bio-lubricant in industrial application.     

Study of degradation kinetics of sunflower oil on H-Beta zeolite

In this study, were studied the degradation of pure sunflower oil and mixed with H-Beta zeolite. This zeolite was synthesized by the hydrothermal method, followed by calcination and ion exchanged. The characterization of the zeolite was performed by X-ray diffraction and nitrogen adsorption/desorption by the method of BET. The analysis showed that H-Beta zeolite presented a good crystallinity and the template was completely removed from the catalyst. The thermal and catalytic degradation study was carried out using the TG/DTG method in multiple heating rates of 5, 10, and 20 °C min⁻¹. The isoconversion method proposed by Vyazovkin was applied to determine the kinetic parameters for degradation of the sunflower oil. The activation energy for the degradation process of pure sunflower oil was 193 kJ mol⁻¹, while for sunflower oil mixed with 20% of H-Beta zeolite was equivalent to 88 kJ mol⁻¹. It was verified that for the degradation of 90% of the sunflower oil mixed with H-Beta, for a period of 1 h, a temperature of 356 °C was required, whereas for the pure vegetable oil, this value was of 387 °C, at the same time period, showing that the catalyst was effective for the degradation process of sunflower oil.     

New Regional Editor

Thermal decomposition of an agrowaste, namely banana trunk fibers (BTF) were investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG) up to 900 °C at different heating rates (from 5 to 100 °C/min). The BTF was subjected to modification by means of various known chemical methods (mercerization, acetylation, peroxide treatment, esterification, and sulfuric acid treatment). Various degradation models, such as the Kissinger, Friedman, and Flynn–Wall–Ozawa were used to determine the apparent activation energy. The obtained apparent activation energy values (149–210 kJ/mol) allow in developing a simplified approach to understand the thermal decomposition behavior of natural fibers as a function of polymer composite processing.     

Thermal decomposition of metal methanesulfonates in air

The thermal decompositions of dehydrated or anhydrous bivalent transition metal (Mn, Fe, Co, Ni, Cu, Zn, Cd) and alkali rare metal (Mg, Ca, Sr, Ba) methanesulfonates were studied by TG/DTG, IR and XRD techniques in dynamic Air at 250–850 °C. The initial decomposition temperatures were calculated from TG curves for each compound, which show the onsets of mass loss of methanesulfonates were above 400 °C. For transition metal methanesulfonates, the pyrolysis products at 850 °C were metal oxides. For alkali rare metal methanesulfonates, the pyrolysis products at 850 °C of Sr and Ba methanesulfonates were sulphates, while those of Mg and Ca methanesulfonate were mixtures of sulphate and oxide.